105 Peer-Reviewed Studies on Medical Marijuana Medical Studies Involving Cannabis and Cannabis Extracts (1990 – 2012)

Studies are listed as Pro, Con, or Not Clearly Pro or Con, based on their conclusions regarding cannabis’ potential medical benefit for the specific purpose being investigated in that study. For example, a study about the effectiveness of using marijuana’s to treat Multiple Sclerosis would be categorized as Pro if the authors concluded that the result was positive. If the results were mixed, the study would be categorized as Not Clearly Pro or Con. A study with negative results would be labeled Con.

Extracts, such as Sativex, are derived directly from the plant, and are not synthetically created. Studies involving man-made substances, such as Marinol, Nabilone, Cannabinor, and others were not included in this review. If there are any peer-reviewed studies involving marijuana that we have not included, please let us know.

Pro

for the specific purpose being investigated in the study

Not Clearly Pro or Con

for the specific purpose being investigated in the study
Con

for the specific purpose being investigated in the study
Totals
Type of Study # of studies % of total # of studies % of total # of studies % of total # of studies % of total
I. Double-Blind Human Studies
12 54.54% 7 31.82% 3 13.64% 22 100%
II. Human Studies
24 30.38% 25 31.65% 30 37.97% 79 100%
III. Animal Studies
4 100% 0 0% 0 0% 4 100%
TOTALS 40 38.09% 32 30.48% 33 31.43% 105 100%

Pro

for the specific purpose being investigated in the study

Not Clearly Pro or Con

for the specific purpose being investigated in the study
Con

for the specific purpose being investigated in the study
Totals
Decade # of studies % of total # of studies % of total # of studies % of total # of studies % of total
2010 – present 5 27.78% 2 11.11% 11 61.11% 18 100%
2000 – 2009 31 40.26% 28 36.36% 18 23.38% 77 100%
1990 – 1999 4 40.00% 2 20.00% 4 40.00% 10 100%
TOTALS  40 38.09% 32 30.48% 33 31.43% 105 100%

 

I. Double-Blind Human Studies
DATE / JOURNAL DESCRIPTION OF STUDY Pro, Con, or Not Clearly Pro or Con for the specific purpose being investigated in the study
22.
Double-Blind

Mar. 1, 2011
European Journal of Neurology

Alena Novotna, MD, et al., stated the following in their Mar. 1, 2011 study titled “A Randomized, Double-blind, Placebo-controlled, Parallel-group, Enriched-design Study of Nabiximols (Sativex), as Add-on Therapy, in Subjects with Refractory Spasticity Caused by Multiple Sclerosis,” published in the European Journal of Neurology:

“Spasticity is a disabling complication of multiple sclerosis, affecting many patients with the condition. Subjects were treated with nabiximols [Sativex], as add-on therapy, in a single-blind manner… This study has shown Sativex to improve spasticity in patients who had failed to respond adequately to other antispasticity medications…”
Mar. 1, 2011 – Alena Novotna, MD

Pro

21.
Double-Blind

Aug. 30, 2010
Canadian Medical Association Journal

Mark A. Ware, MD, MSc, et al., stated the following in their Aug. 30, 2010 study titled “Smoked Cannabis for Chronic Neuropathic Pain: A Randomized Controlled Trial,” published in the Canadian Medical Association Journal:

“Adults with post-traumatic or postsurgical neuropathic pain were randomly assigned to receive cannabis at four potencies (0%, 2.5%, 6% and 9.4% tetrahydrocannabinol) over four 14-day periods in a crossover trial. Participants inhaled a single 25-mg dose through a pipe three times daily for the first five days in each cycle, followed by a nine-day washout period. Daily average pain intensity was measured using an 11-point numeric rating scale.

Conclusion

A single inhalation of 25 mg of 9.4% tetrahydrocannabinol herbal cannabis three times daily for five days reduced the intensity of pain, improved sleep and was well tolerated.”
Aug. 30, 2010 – Mark A. Ware, MD, MSc

Pro

20.
Double-Blind

Nov. 6, 2009
Journal of Pain and Symptom Management

Jeremy R. Johnson, MBChB, Medical Director at the Shropshire and Mid Wales Severn Hospice, et. al, wrote the following in a Nov. 2009 article titled “Multicenter, Double-Blind, Randomized, Placebo-Controlled, Parallel-Group Study of the Efficacy, Safety, and Tolerability of THC:CBD Extract and THC Extract in Patients With Intractable Cancer-Related Pain,” published on the Journal of Pain and Symptom Management website:

“The primary analysis of change from baseline in mean pain Numerical Rating Scale (NRS) score was statistically significantly in favor of THC:CBD compared with placebo…

Conclusion
This study shows that THC:CBD extract is efficacious for relief of pain in patients with advanced cancer pain not fully relieved by strong opioids.”
Nov. 6, 2009 – Jeremy R. Johnson, MBChB

Pro

19.
Double-Blind

Aug. 2008
Neuropsychopharmacology

Ronald J. Ellis, MD, PhD, Professor In Residence in the Department of Neuroscience at the University of California at San Diego, et al., stated the following in their Aug. 2008 study titled “Smoked Medicinal Cannabis for Neuropathic Pain in HIV: A Randomized, Crossover Clinical Trial,” published in Neuropsychopharmacology:

“In a double-blind, randomized, clinical trial of the short-term adjunctive treatment of neuropathic pain in HIV-associated distal sensory polyneuropathy, participants received either smoked cannabis or placebo cannabis cigarettes…

Among completers, pain relief was significantly greater with cannabis than placebo. The proportion of subjects achieving at least 30% pain relief was again significantly greater with cannabis (46%) compared to placebo (18%). It was concluded that smoked cannabis was generally well-tolerated and effective when added to concomitant analgesic therapy in patients with medically refractory pain due to HIV-associated neuropathy.”
Aug. 2008 – Ronald J. Ellis, MD, PhD

Pro

18.
Double-Blind

Aug. 2008
European Neuropsychopharmacology

Patrik Roser, PhD, Professor of Psychiatry at Ruhr-University Bochum (Germany), et al., wrote in their Aug. 2008 article “Effects of Acute Oral Delta9-tetrahydrocannabinol and Standardized Cannabis Extract on the Auditory P300 Event-related Potential in Healthy Volunteers” in European Neuropsychopharmacology:

“Reduced amplitudes of auditory evoked P300 are a robust finding in schizophrenic patients, indicating deficient attentional resource allocation and active working memory. Delta9-Tetrahydrocannabinol (Delta9-THC), the main active constituent of Cannabis sativa, has been known to acutely impair cognitive abilities in several domains, particularly in memory and attention. Given the psychotic-like effects of Delta9-THC, a cannabinoid hypothesis of schizophrenia has been proposed. This prospective, double-blind, placebo-controlled cross-over study investigated the acute effects of cannabinoids on P300 amplitude in 20 healthy volunteers (age 28.2+/-3.1 years, 10 male) by comparing Delta9-THC and standardized cannabis extract containing Delta9-THC and cannabidiol (CBD)… CBD has been known to abolish many of the psychotropic effects of Delta9-THC, but, unexpectedly, failed to demonstrate a reversal of Delta9-THC-induced P300 reduction… These data suggest that Delta(9)-THC may lead to acute impairment of attentional functioning and working memory.”
Aug. 2008 – Patrik Roser, PhD, MD

Con

17.
Double-Blind

June 2008
Journal of Pain

Barth Wilsey, MD, Director of the University of California at Davis Analgesic Research Center, et al., stated the following in their June 2008 study titled “A Randomized, Placebo Controlled Cross-Over Trial of Cannabis Cigarettes in Neuropathic Pain,” published in the Journal of Pain:

“This study’s objective was to examine the efficacy of two doses of smoked cannabis on pain in persons with neuropathic pain of different origins (e.g., physical trauma to nerve bundles, spinal cord injury, multiple sclerosis, diabetes). In a double-blind, randomized clinical trial participants received either lowdose, high-dose, or placebo cannabis cigarettes…

Thirty-eight patients underwent a standardized procedure for smoking either high-dose (7%), low-dose (3.5%), or placebo cannabis; of these, 32 completed all three smoking sessions. The study demonstrated an analgesic response to smoking cannabis with no significant difference between the low and the high dose cigarettes. The study concluded that both low and high cannabis doses were efficacious in reducing neuropathic pain of diverse causes.”
June 2008 – Barth Wilsey, MD

Pro

16.
Double-Blind

Nov. 2007
Anesthesiology

Mark Wallace, MD, Professor of Anesthesiology at the University of California at San Diego, et al., stated the following in their Nov. 2007 article titled “Dose-Dependent Effects of Smoked Cannabis on Capsaicin-Induced Pain and Hyperalgesia in Healthy Volunteers,” published in the journal Anesthesiology:

“In summary, in this model of human experimental pain, smoked cannabis was demonstrated to have a delayed biphasic [two phase] effect on pain scores induced by intradermal capsaicin [chili pepper heat injected into the skin]. The low dose [of marijuana] had no effect, the medium dose significantly reduced the pain and the high dose significantly increased the pain… No conclusions on the analgesic efficacy of smoked cannabis on clinical pain states can be made from this study as the relationship between analgesic effects in experimental pain and clinical pain states is unknown.”
Nov. 2007 – Mark Wallace, MD

Not Clearly Pro or Con

15.
Double-Blind

Mar. 2007
European Journal of Neurology

Christine Collin, MD, Senior Consultant in Neuro-rehabilitation at the Royal Berkshire and Battle Hospitals, et al., wrote the following in their article “Randomized Controlled Trial of Cannabis-Based Medicine in Spasticity Caused by Multiple Sclerosis,” published in the Mar. 2007European Journal of Neurology:

 “Symptoms relating to spasticity are common in multiple sclerosis (MS) and can be difficult to treat. We have investigated the efficacy, safety and tolerability of a standardized … cannabis-based medicine (CBM) containing delta-9 tetrahydrocannabinol (THC) and cannabidiol (CBD), upon spasticity in MS. A total of 189 subjects with definite MS and spasticity were randomized to receive daily doses of active preparation (n = 124) or placebo (n = 65) in a double blind study over 6 weeks…

The primary efficacy analysis… showed the active preparation to be significantly superior…

We conclude that this CBM [cannabis-based medicine] may represent a useful new agent for treatment of the symptomatic relief of spasticity in MS.”
Mar. 2007 – Christine Collin, MD

Pro

14.
Double-Blind

Feb. 13, 2007
Neurology

Donald Abrams, MD, Professor of Clinical Medicine at the University of California at San Francisco, et al. wrote in their Feb. 13, 2007 article titled “Cannabis in Painful HIV-Associated Sensory Neuropathy: A Randomized Placebo-Controlled Trial” in the journal Neurology:

“Objective: To determine the effect of smoked cannabis on the neuropathic pain of HIV-associated sensory neuropathy, and an experimental pain model…

Patients were randomly assigned to smoke either cannabis (3.56% thc) or identical placebo cigarettes with the cannabinoids extracted three times daily for 5 days…

Conclusion: Smoked cannabis was well tolerated and effectively relieved chronic neuropathic pain from HIV-associated sensory neuropathy The findings are comparable to oral drugs used for chronic neuropathic pain.”
Feb. 13, 2007 – Donald Abrams, MD

Pro

13.
Double-Blind

Oct. 2006
Journal of Glaucoma

Ileana Tomida, MD, Ophthalmology Specialist, et al. wrote in an Oct. 2006 article titled “Effect of Sublingual Application of Cannabinoids on Intraocular Pressure: A Pilot Study” in the Journal of Glaucoma:

“PURPOSE: The purpose of this study was to assess the effect on intraocular pressure (IOP) and the safety and tolerability of oromucosal administration of a low dose of delta-9-tetrahydrocannabinol (Delta-9-THC) and cannabidiol (CBD)…

CONCLUSIONS: A single 5 mg sublingual dose of Delta-9-THC reduced the IOP temporarily and was well tolerated by most patients. Sublingual administration of 20 mg CBD did not reduce IOP, whereas 40 mg CBD produced a transient increase IOP rise.”
Oct. 2006 – Ileana Tomida, MD

Not Clearly Pro or Con

12.
Double-Blind

July 2006
Journal of Clinical Oncology

Florian Strasser, MD, Assistant Medical Director of the Swiss Society of Palliative Care et al., wrote in a July 2006 article titled “Comparison of Orally Administered Cannabis Extract and Delta-9-Tetrahydrocannabinol in Treating Patients with Cancer-Related Anorexia-Cachexia Syndrome: A Multicenter, Phase III, Randomized, Double-Blind, Placebo-Controlled Clinical Trial From The Cannabis-in-Cachexia-Study-Group” in the Journal of Clinical Oncology:

“PURPOSE: To compare the effects of cannabis extract (CE), delta-9-tetrahydrocannabinol (THC), and placebo (PL) on appetite and quality of life (QOL) in patients with cancer-related anorexia-cachexia syndrome (CACS)…

CONCLUSION: CE at the oral dose administered was well tolerated by these patients with CACS. No differences in patients’ appetite or QOL were found either between CE, THC, and PL or between CE and THC at the dosages investigated.”
July 2006 – Florian Strasser, MD

Not Clearly Pro or Con

11.
Double-Blind

Dec. 2005
Journal of Neurology, Neurosurgery and Psychiatry

John P. Zajicek, PhD, Professor of Clinical Neuroscience at the Neurology Research and Clinical Trials Unit of the Peninsula Medical School at the University of Plymouth, et al., wrote the following in a Dec. 2005 article titled “Cannabinoids in Multiple Sclerosis (CAMS) Study: Safety and Efficacy Data for 12 Months Follow Up” in the Journal of Neurology, Neurosurgery and Psychiatry:

“OBJECTIVE: To test the effectiveness and long term safety of cannabinoids in multiple sclerosis (MS), in a follow up to the main Cannabinoids in Multiple Sclerosis (CAMS) study…

RESULTS: Intention to treat analysis of data from the 80% of patients followed up for 12 months showed evidence of a small treatment effect on muscle spasticity as measured by change in Ashworth score from baseline to 12 months…There was suggestive evidence for treatment effects of Delta(9)-THC on some aspects of disability. There were no major safety concerns. Overall, patients felt that these drugs were helpful in treating their disease…CONCLUSIONS: These data provide limited evidence for a longer term treatment effect of cannabinoids. A long term placebo controlled study is now needed to establish whether cannabinoids may have a role beyond symptom amelioration in MS.”
Dec. 2005 – John P. Zajicek, PhD

Not Clearly Pro or Con

10.
Double-Blind

Sep. 2005
Neurology

David J. Rog, PhD, from the Walton Centre for Neurology and Neurosurgery at the University of Liverpool, et al., wrote in a Sep. 2005 article titled “Randomized, Controlled Trial of Cannabis-Based Medicine in Central Pain in Multiple Sclerosis” in the journal Neurology:

“BACKGROUND: Central pain in multiple sclerosis (MS) is common and often refractory to treatment…

CONCLUSIONS: Cannabis-based medicine is effective in reducing pain and sleep disturbance in patients with multiple sclerosis related central neuropathic pain and is mostly well tolerated.”
Sep. 2005 – David J. Rog, PhD

Pro

9.
Double-Blind

Dec. 2004
Pain

Jonathan S. Berman, MA, Consulting Anaesthetist at the Royal National Orthopaedic Hospital, et al., wrote the following in a Dec. 2004 article titled “Efficacy of Two Cannabis Based Medicinal Extracts for Relief of Central Neuropathic Pain from Brachial Plexus Avulsion: Results of a Randomised Controlled Trial” in the journal Pain:

“The objective was to investigate the effectiveness of cannabis-based medicines for treatment of chronic pain associated with brachial plexus root avulsion. This condition is an excellent human model of central neuropathic pain as it represents an unusually homogenous group in terms of anatomical location of injury, pain descriptions and patient demographics…

The primary outcome measure was the mean pain severity score during the last 7 days of treatment. Secondary outcome measures included pain related quality of life assessments. The primary outcome measure failed to fall by the two points defined in our hypothesis. However, both this measure and measures of sleep showed statistically significant improvements.The study medications were generally well tolerated with the majority of adverse events, including intoxication type reactions, being mild to moderate in severity and resolving spontaneously. Studies of longer duration in neuropathic pain are required to confirm a clinically relevant, improvement in the treatment of this condition.”
Dec. 2004 – Jonathan S. Berman, MA

Pro

8.
Double-Blind

Oct. 2004
Neurology

Camille B. Carroll, PhD, Clinical Research Fellow at the Peninsula College of Medicine and Dentistry, et al., wrote in an Oct. 2004 article titled “Cannabis For Dyskinesia In Parkinson Disease: A Randomized Double-blind Crossover Study” in the journal Neurology:

“Seventeen patients completed the RCT. Cannabis was well tolerated, and had no pro- or antiparkinsonian action. There was no evidence for a treatment effect on levodopa-induced dyskinesia as assessed by the UPDRS, or any of the secondary outcome measures.

CONCLUSIONS: Orally administered cannabis extract resulted in no objective or subjective improvement in dyskinesias or parkinsonism.”
Oct. 2004 – Camille B. Carroll, PhD

Not Clearly Pro or Con

7.
Double-Blind

Aug. 2004
Multiple Sclerosis

Derick T. Wade, MD, Professor in the Department of Clinical Neurology at the University of Oxford, et al., wrote the following in an Aug. 2004 article titled “Do Cannabis-based Medicinal Extracts Have General Or Specific Effects on Symptoms in Multiple Sclerosis? A Double-blind, Randomized, Placebo-controlled Study on 160 Patients,” published in the journal Multiple Sclerosis:

“The primary outcome measure was a Visual Analogue Scale (VAS) score for each patient’s most troublesome symptom. Additional measures included VAS scores of other symptoms, and measures of disability, cognition, mood, sleep and fatigue. Following CBME the primary symptom score reduced from mean (SE) 74.36 (11.1) to 48.89 (22.0) following CBME and from 74.31 (12.5) to 54.79 (26.3) following placebo [ns].

Spasticity VAS scores were significantly reduced by CBME (Sativex) in comparison with placebo (P=0.001). There were no significant adverse effects on cognition or mood and intoxication was generally mild.”
Aug. 2004 – Derick T. Wade, MD

Pro

6.
Double-Blind

Aug. 2004
Multiple Sclerosis

Claude Vaney, MD, Medical Director of the Neurological Rehabilitation and MS Centre, Montana, Switzerland, et al., wrote in an Aug. 2004 article titled “Efficacy of Tetrahydrocannabinol in Patients Refractory to Standard Antiemetic Therapy. Efficacy, Safety and Tolerability of an Orally Administered Cannabis Extract in the Treatment of Spasticity in Patients with Multiple Sclerosis: A Randomized, Double-blind, Placebo-controlled, Crossover Study” in the journal Multiple Sclerosis:

“In the 50 patients included into the intention-to-treat analysis set, there were no statistically significant differences associated with active treatment compared to placebo, but trends in favour of active treatment were seen for spasm frequency, mobility and getting to sleep.

In the 37 patients (per-protocol set) who received at least 90% of their prescribed dose, improvements in spasm frequency (P = 0.013) and mobility after excluding a patient who fell and stopped walking were seen (P = 0.01). Minor adverse events were slightly more frequent and severe during active treatment, and toxicity symptoms, which were generally mild, were more pronounced in the active phase.

CONCLUSION: A standardized Cannabis sativa plant extract might lower spasm frequency and increase mobility with tolerable side effects in MS patients with persistent spasticity not responding to other drugs.”
Aug. 2004 – Claude Vaney, MD

Pro

5.
Double-Blind

Apr. 2004
Neurology

Patrick Fox, MD, Clinical Neurologist at the Peninsula Medical School at the University of Plymouth, et al., wrote in an Apr. 2004 article titled “The Effect of Cannabis on Tremor in Patients with Multiple Sclerosis” in the journal Neurology:

“BACKGROUND: Disabling tremor is common in patients with multiple sclerosis (MS). Data from animal model experiments and subjective and small objective studies involving patients suggest that cannabis may be an effective treatment for tremor associated with MS. To our knowledge, there are no published double-blind randomized controlled trials of cannabis as a treatment for tremor in MS patients…

RESULTS: Analysis of the data showed no significant improvement in any of the objective measures of upper limb tremor with cannabis extract compared to placebo. Finger tapping was faster on placebo compared to cannabis extract (p < 0.02). However, there was a nonsignificant trend for patients to experience more subjective relief from their tremors while on cannabis extract compared to placebo.

CONCLUSIONS: Cannabis extract does not produce a functionally significant improvement in MS-associated tremor.”
Apr. 2004 – Patrick Fox, MD

Not Clearly Pro or Con

4.
Double-Blind

Feb. 2003
Clinical Rehabilitation

Derick T. Wade, MD, Professor in the Department of Clinical Neurology at the University of Oxford, et al., wrote in a Feb. 2003 article titled “A Preliminary Controlled Study to Determine Whether Whole-Plant Cannabis Extracts Can Improve Intractable Neurogenic Symptoms” in the journal Clinical Rehabilitation:

“OBJECTIVES: To determine whether plant-derived cannabis medicinal extracts (CME) can alleviate neurogenic symptoms unresponsive to standard treatment, and to quantify adverse effects…

Measures used: Patients recorded symptom, well-being and intoxication scores on a daily basis using visual analogue scales. At the end of each two-week period an observer rated severity and frequency of symptoms on numerical rating scales, administered standard measures of disability (Barthel Index), mood and cognition, and recorded adverse events.RESULTS: Pain relief associated with both THC and CBD was significantly superior to placebo. Impaired bladder control, muscle spasms and spasticity were improved by CME in some patients with these symptoms. Three patients had transient hypotension and intoxication with rapid initial dosing of THC-containing CME.

CONCLUSIONS: Cannabis medicinal extracts can improve neurogenic symptoms unresponsive to standard treatments. Unwanted effects are predictable and generally well tolerated. Larger scale studies are warranted to confirm these findings.”
Feb. 2003 – Derick T. Wade, MD

Pro

3.
Double-Blind

May 2002
Neurology

Joep Killestein, MD, PhD, Multiple Sclerosis Researcher in the Department of Neurology at the MS Centre at VU Medical Centre in Amsterdam, et al., wrote in a May 2002 article titled “Safety, Tolerability, and Efficacy of Orally Administered Cannabinoids in MS” in the journalNeurology:

“The authors conducted a randomized, double-blind, placebo-controlled, twofold crossover study in 16 patients with MS who presented with severe spasticity to investigate safety, tolerability, and efficacy of oral Delta(9)-Tetrahydrocannabinol (THC) and Cannabis sativa plant extract. Both drugs were safe, but adverse events were more common with plant-extract treatment. Compared with placebo, neither THC nor plant-extract treatment reduced spasticity. Both THC and plant-extract treatment worsened the participant’s global impression.”
May 2002 – Joep Killestein, MD, PhD

Con

2.
Double-Blind

Mar. 1994
Clinical Pharmacology and Therapeutics

Harry S. Greenberg, MD, Professor in the Department of Neurology at the University of Michigan, et al., wrote the following in their Mar. 1994 article titled “Short-term Effects of Smoking Marijuana on Balance in Patients with Multiple Sclerosis and Normal Volunteers,” published in the journal Clinical Pharmacology and Therapeutics:

“A double-blind randomised placebo-controlled study of inhaled marijuana smoke on postural responses was performed in 10 adult patients with spastic multiple sclerosis (MS) and 10 normal volunteers matched as closely as possible for age, sex, and weight. A computer-controlled dynamic posturographic platform with a video line scan camera measured shoulder displacement in response to pseudorandom platform movements.

Pre-marijuana smoking patient tracking was inferior to that of the normal volunteers as indicated by the higher noise variance of the former.

Smoking one marijuana cigarette containing 1.54% Delta-9-tetrahydrocannabinol increased postural tracking error in both the patients and normal control subjects with both eyes open and closed; this untoward effect was greatest for the patients. The tracking error was also accompanied by a decrease in response speed for the patients with their eyes closed.

Marijuana smoking further impairs posture and balance in patients with spastic MS.”
Mar. 1994 – Harry S. Greenberg, MD

Con

1.
Double-Blind

Nov. 1991
Pharmacology, Biochemistry and Behavior

Paul F. Consroe, PhD, Professor Emeritus in the Department of Pharmacology and Toxicology at the University of Arizona, et al., wrote the following in their Nov. 1991 article titled “Controlled Clinical Trial of Cannabidiol in Huntington’s Disease,” published in the journal Pharmacology, Biochemistry and Behavior:

“Based on encouraging preliminary findings, cannabidiol (CBD), a major nonpsychotropic constituent of Cannabis, was evaluated for symptomatic efficacy and safety in 15 neuroleptic-free patients with Huntington’s Disease (HD). The effects of oral CBD (10 mg/kg/day for 6 weeks) and placebo (sesame oil for 6 weeks) were ascertained weekly under a double-blind, randomized cross-over design…

In summary, CBD, at an average daily dose of about 700 mg/day for 6 weeks, was neither symptomatically effective nor toxic, relative to placebo, in neuroleptic-free patients with HD.”
Nov. 1991 – Paul F. Consroe, PhD

Not Clearly Pro or Con

 

II. Human Studies
BACK TO TOP

 

DATE / JOURNAL DESCRIPTION OF STUDY Pro, Con, or Not Clearly Pro or Con for the specific purpose being investigated in the study
79.
Human Studies

July 2012
PLoS ONE

Gustaaf Albert Dekker, MD, PhD, Professor in the Department of Obstetrics and Gynaecology at the University of Adelaide, et al., stated the following in their July 2012 study titled “Risk Factors for Preterm Birth in an International Prospective Cohort of Nulliparous Women,” published in PLoS ONE:

“Regular marijuana use up to conception was a significant and strong risk factor [for SPTB-IM, spontaneous preterm birth with intact membranes]…We have shown that marijuana is a strong environmental risk factor or SPTB-IM in this population. We are unable to determine whether this association is due to a toxic effect of marijuana or is a marker of a suite of lifestyle factors that contribute to the risk.”
July 2012 – Gustaaf Albert Dekker, MD, PhD

Con

78.
Human Studies

May 2012
Psychiatry Research

Raphael J. Braga, MD, Assistant Professor of Psychiatry at Hofstra North Shore-LIJ School of Medicine, et al., stated the following in their May 2012 study titled “Cognitive and Clinical Outcomes Associated with Cannabis Use in Patients with Bipolar I Disorder,” published in Psychiatry Research:

“The objective of the present study was to compare clinical and neurocognitive measures in individuals with bipolar disorder with a history of cannabis use disorder (CUD) versus those without a history of CUD…Results from our analysis suggest that subjects with bipolar disorder and history of CUDs demonstrate significantly better neurocognitive performance, particularly on measures of attention, processing speed, and working memory…

These data could be interpreted to suggest that cannabis use may have a beneficial effect on cognitive functioning in patients with severe psychiatric disorders. However, it is also possible that these findings may be due to the requirement for a certain level of cognitive function and related social skills in the acquisition of illicit drugs.”
May 2012 – Raphael J. Braga, MD

Pro

77.
Human Studies

Jan. 2012
Journal of the American Medical Association

Mark J. Pletcher, MD, MPH, Associate Professor, In Residence, in the Departments of Epidemiology, Biostatistics, and Medicine at the University of California at San Francisco, et al., stated the following in their Jan. 2012 study titled “Association Between Marijuana Exposure and Pulmonary Function over 20 Years. The Coronary Artery Risk Development in Young Adults (CARDIA) Study,” published in the Journal of the American Medical Association:

“In this 20-year study of marijuana and pulmonary function [n=5,115], we confirmed the expected reductions in FEV1 [forced expiratory volume in the first second of expiration] and FVC [forced vital capacity] from tobacco use. In contrast, marijuana use was associated with higher FEV1 and FVC at the low levels of exposure typical for most marijuana users… we found no evidence that increasing exposure to marijuana adversely affects pulmonary function. Marijuana may have beneficial effects on pain control, appetite, mood, and management of other chronic symptoms. Our findings suggest that occasional use of marijuana for these or other purposes may not be associated with adverse consequences on pulmonary function. It is more difficult to estimate the potential effects of regular heavy use, because this pattern of use is relatively rare in our study sample; however, our findings do suggest an accelerated decline in pulmonary function with heavy use and a resulting need for caution and moderation when marijuana use is considered.”
Jan. 2012 – Mark J. Pletcher, MD, MPH

Pro

76.
Human Studies

May 2012
Schizophrenia Research

Deidre M. Anglin, PhD, Assistant Professor of Clinical Psychology at the City College and Graduate Center, City University of New York, et al., wrote the following in their May 2012 article “Early Cannabis Use and Schizotypal Personality Disorder Symptoms from Adolescence to Middle Adulthood,” published in Schizophrenia Research:

“Prospective data from 804 participants was used to determine associations between early cannabis use and later schizotypal symptoms… Cannabis use with onset prior to age 14 strongly predicted SPD [schizotypal personality disorder] symptoms in adulthood, independent of early adolescent SPD symptoms, major depression, anxiety disorder, other drug use, and cigarette use…

Our data provide further support for a strong association of early cannabis use with the development of symptoms characteristic of schizophrenia spectrum disorders. As with studies in schizophrenia, early SPD symptoms could not fully explain the association of early cannabis use with later schizotypal symptoms.”
May 2012 – Deidre M. Anglin, PhD

Con

75.
Human Studies

Jan. 11, 2012
Journal of the American Medical Association

Mark J. Pletcher, MD, MPH, et al., wrote the following in their Jan. 11, 2012 article titled “Association Between Marijuana Exposure and Pulmonary Function Over 20 Years,” published in the Journal of the American Medical Association:

“In this 20-year study of marijuana and pulmonary function, we confirmed the expected reductions in FEV [forced expiratory volume in first second of expiration] and FVC [forced vital capacity] from tobacco use. In contrast, marijuana use was associated with higher FEV and FVC at the low levels of exposure typical for most marijuana users [2-3 episodes in the last 30 days]… Although our sample contained insufficient numbers of heavy users to confirm a detrimental effect of very heavy marijuana use on pulmonary function, our findings suggest this possibility.

Marijuana may have beneficial effects on pain control, appetite, mood, and management of other chronic symptoms. Our findings suggest that occasional use of marijuana for these or other purposes may not be associated with adverse consequences on pulmonary function. It is more difficult to estimate the potential effects of regular heavy use, because this pattern of use is relatively rare in our study sample; however, our findings do suggest an accelerated decline in pulmonary function with heavy use and a resulting need for caution and moderation when marijuana use is considered.”
Jan. 11, 2012 – Mark J. Pletcher, MD, MPH

Pro

74.
Human Studies

July 12, 2011
Acta Psychiatrica Scandinavica

D.H. Linszen, PhD, MD, Professor Emeritus of Psychiatry at the University of Amsterdam, et al., wrote in their July 12, 2011 article “Cannabis Use and Age at Onset of Symptoms in Subjects at Clinical High Risk for Psychosis” in Acta Psychiatrica Scandinavica:

“Objective: Numerous studies have found a robust association between cannabis use and the onset of psychosis. Nevertheless, the relationship between cannabis use and the onset of early (or, in retrospect, prodromal) symptoms of psychosis remains unclear. The study focused on investigating the relationship between cannabis use and early and high-risk symptoms in subjects at clinical high risk for psychosis.

Results: Younger age at onset of cannabis use or a cannabis use disorder was significantly related to younger age at onset of six symptoms. Onset of cannabis use preceded symptoms in most participants.

Conclusion: Our results provide support that cannabis use plays an important role in the development of psychosis in vulnerable individuals. Cannabis use in early adolescence should be discouraged.”
July 12, 2011 – D.H. Linszen, PhD, MD

Con

73.
Human Studies

Mar. 29, 2011
Neurology

Anthony Feinstein, PhD, MD, Professor of Psychiatry at the University of Toronto, et al., wrote in their Mar. 29, 2011 article “Effects of Cannabis on Cognitive Function in Patients with Multiple Sclerosis” in Neurology:

“Given that MS is associated with cognitive deterioration, the aim of this study was to determine the neuropsychological effects of cannabis use in this population.

Results: Cannabis users performed significantly more poorly than nonusers on measures of information processing speed, working memory, executive functions, and visuospatial perception. They were also twice as likely as nonusers to be classified as globally cognitively impaired.”
Mar. 29, 2011 – Anthony Feinstein, PhD, MD

Con

72.
Human Studies

Mar. 9, 2011
Schizophrenia Bulletin

Verity C. Leeson, MD, PhD, Honorary Research Associate at the University College London (UCL) Institute of Neurology, et al., wrote in their Mar. 9, 2011 article “The Effect of Cannabis Use and Cognitive Reserve on Age at Onset and Psychosis Outcomes in First-Episode Schizophrenia” in the Schizophrenia Bulletin:

“Objective: Cannabis use is associated with a younger age at onset of psychosis, an indicator of poor prognosis, but better cognitive function, a positive prognostic indicator. We aimed to clarify the role of age at onset and cognition on outcomes in cannabis users with first-episode schizophrenia as well as the effect of cannabis dose and cessation of use… Conclusions: Cannabis use brings forward the onset of psychosis in people who otherwise have good prognostic features indicating that an early age at onset can be due to a toxic action of cannabis rather than an intrinsically more severe illness. Many patients abstain over time, but in those who persist, psychosis is more difficult to treat.”
Mar. 9, 2011 – Verity C. Leeson, MD, PhD

Con

71.
Human Studies

Mar. 1, 2011
British Medical Journal

Jim van Os, PhD, MD, Professor of Psychiatry at Maastricht University Medical Centre, et al., wrote in their Mar. 1, 2011 article “Continued Cannabis Use and Risk of Incidence and Persistence of Psychotic Symptoms: 10 Year Follow-up Cohort Study” in the British Medical Journal:

“Cannabis use is a risk factor for the development of incident psychotic symptoms. Continued cannabis use might increase the risk for psychotic disorder by impacting on the persistence of symptoms.
Mar. 1, 2011 – Jim van Os, PhD, MD

Con

70.
Human Studies

Mar. 2011
Schizophrenia Research

Marc de Hert, PhD, MD, Clinical Psychiatrist and Psychotherapist in the University Psychiatric Centre at Katholieke Universiteit Leuven (Belgium), et al., wrote in their Mar. 2011 article “Effects of Cannabis Use on Age at Onset in Schizophrenia and Bipolar Disorder” in Schizophrenia Research:

“BACKGROUND: Cannabis use may decrease age at onset in both schizophrenia and bipolar disorder, given the evidence for substantial phenotypic and genetic overlap between both disorders.

RESULTS: Cannabis and other substance use was more frequent in patients with schizophrenia compared to the bipolar group. Both cannabis use and a schizophrenia diagnosis predicted earlier age at onset. There was a significant interaction between cannabis use and diagnosis, cannabis having a greater effect in bipolar patients. Age at onset in users of cannabis was comparable in both diagnostic groups whereas bipolar non-users were significantly older than schizophrenia non-users at onset.

CONCLUSION: Cannabis use may decrease age at onset in both schizophrenia and bipolar patients and reduce the effect of diagnosis. This is consistent with the view that cannabis use may unmask a pre-existing genetic liability that is partly shared between patients with schizophrenia and bipolar disorder.”
Mar. 2011 – Marc de Hert, PhD, MD

Con

69.
Human Studies

Feb. 7, 2011
Archives of General Psychiatry

Matthew Large, MBBS, Senior Lecturer at the University of New South Wales, et. al, wrote the following in their Feb. 7, 2011 article titled “Cannabis Use and Earlier Onset of Psychosis: A Systematic Meta-analysis,” published in the Archives of General Psychiatry:

“The results of meta-analysis provide evidence for a relationship between cannabis use and earlier onset of psychotic illness, and they support the hypothesis that cannabis use plays a causal role in the development of psychosis in some patients. The results suggest the need for renewed warnings about the potentially harmful effects of cannabis.
Feb. 7, 2011 – Matthew Large, MBBS

Con

68.
Human Studies

July 2010
Schizophrenia Research

Serge Sevy, MD, MBA, Adjunct Associate Professor of Clinical Psychiatry and Behavioral Sciences at the Albert Einstein College of Medicine, et al., wrote in their July 2010 article “Are Cannabis Use Disorders Associated with an Earlier Age at Onset of Psychosis? A Study in First Episode Schizophrenia” in Schizophrenia Research:

“[A]lthough cannabis use precedes the onset of illness in most patients, there was no significant association between onset of illness and CUD (cannabis use disorders) that was not accounted by demographic and clinical variables. Previous studies implicating CUD in the onset of schizophrenia may need to more comprehensively assess the relationship between CUD and schizophrenia, and take into account additional variables that we found associated with CUD.
July 2010  – Serge Sevy, MD, MBA

Not Clearly Pro or Con

67.
Human Studies

June 2010
British Journal of Psychiatry

Cécile Henquet, PhD, Researcher in the Department of Psychiatry and Neuropsychology at Maastricht University, et al., wrote the following in their June 2010 article titled “Psychosis Reactivity to Cannabis Use in Daily Life: An Experience Sampling Study,” published in the British Journal of Psychiatry:

“Cannabis use in daily life was associated with subsequent increases in hallucinatory experiences, in particular auditory hallucinations. Patients with a psychotic disorder [such as schizophrenia or schizoaffective disorder] were more sensitive to the hallucinogenic effects of cannabis than healthy controls… The data suggest that the positive effects of cannabis on mood are acute [occurring in the short term] whereas its association with psychotic experiences is sub-acute [occurring in the longer term].”
June 2010 – Cécile Henquet , PhD

Con

66.
Human Studies

May 2010
Drug and Alcohol Review

Silvia Minozzi, MD, MS, Professor of Epidemiology at Local Health Unit Roma E (Italy), et al., wrote in their May 2010 article titled “An Overview of Systematic Reviews on Cannabis and Psychosis: Discussing Apparently Conflicting Results,” in Drug and Alcohol Review:

Issues. Cannabis intoxication can lead to acute, transient psychotic symptoms and the short-term exacerbation of pre-existing psychotic symptoms. However, controversy exists about whether cannabis can actually cause long-term psychosis.

Key Findings. We included five systematic reviews. Four of the reviews performed a meta-analysis and showed a consistent association between cannabis use and psychosis; the fifth review considered psychological problems more broadly, did not perform a meta-analysis and reported an inconsistent association. The reasons for discordance were: different outcomes (psychosis vs. psychological problems), different inclusion criteria for primary studies and different methods for summarising the results.

Implications. This overview shows a consistent association between cannabis use and psychotic symptoms, though it is not possible to draw firm conclusions about a causal relationship. Reverse causality and residual confounding cannot be excluded. An interaction with other environmental and genetic factors is difficult to ascertain.

Conclusion. We conclude that there is insufficient knowledge to determine the level of risk associated with cannabis use in relation to psychotic symptoms and that more information is needed on both the risks of cannabis use and the benefits of preventive interventions to support evidence-based approaches in this area.”
May 2010 – Silvia Minozzi, MD, MS

Not Clearly Pro or Con

65.
Human Studies

May 2010
Archives of General Psychiatry

John McGrath, MBBS, MD, PhD, Director of Developmental Neurobiology at the Queensland Center for Mental Health Research, et al., wrote in their May 2010 article titled “Association Between Cannabis Use and Psychosis-Related Outcomes Using Sibling Pair Analysis in a Cohort of Young Adults,” in the Archives of General Psychiatry:

“Longer duration since first cannabis use was associated with multiple psychosis-related outcomes in young adults… the longer the duration since first cannabis use, the higher the risk of psychosis-related outcomes…

Compared with those who had never used cannabis, young adults who had 6 or more years since first use of cannabis (i.e., who commenced use when around 15 years or younger) were twice as likely to develop a nonaffective psychosis…

This study provides further support for the hypothesis that early cannabis use is a risk-modifying factor for psychosis-related outcomes in young adults.”
May 2010 – John McGrath, MBBS, MD, PhD

Con

64.
Human Studies

Feb. 2010
European Archives of Psychiatry and Clinical Neuroscience

Patrik Roser, PhD, Patrik Roser, PhD, Professor of Psychiatry at Ruhr-University Bochum (Germany), et al., wrote in their Feb. 2010 article “Auditory Mismatch Negativity Deficits in Long-term Heavy Cannabis Users” in the European Archives of Psychiatry and Clinical Neuroscience:
“Mismatch negativity (MMN) is an auditory event-related potential indicating auditory sensory memory and information processing. The present study tested the hypothesis that chronic cannabis use is associated with deficient MMN generation… The results indicate that chronic cannabis use may cause a specific impairment of auditory information processing. In particular, duration and quantity of cannabis use could be identified as important factors of deficient MMN generation.

Feb. 2010 – Patrik Roser, PhD, MD

Con

63.
Human Studies

Sep. 2009
Schizophrenia Research

Martin Frisher, PhD, Senior Lecturer in Health Services Research at Keele University, et al., wrote in their Sep. 2009 article “Assessing the Impact of Cannabis Use on Trends in Diagnosed Schizophrenia in the United Kingdom from 1996 to 2005” in Schizophrenia Research:
“The results of this study indicate that the incidence and prevalence of diagnoses of schizophrenia and psychoses in general practice did not increase between 1996 and 2005…
This study does not therefore support the specific causal link between cannabis use and the incidence of psychotic disorders…
The most parsimonious explanation of the results reported here are that the schizophrenia/psychoses data presented here are valid and the causal models linking cannabis with schizophrenia/psychoses are not supported by this study.”

Sep. 2009 – Martin Frisher, PhD

Not Clearly Pro or Con

62.
Human Studies

Sep. 2009
Neuroscience Letters

Patrik Roser, PhD, Patrik Roser, PhD, Professor of Psychiatry at Ruhr-University Bochum (Germany), et al., wrote in their Sep. 2009 article “No Association Between Chronic Cannabis Use and Loudness Dependence of Auditory Evoked Potentials as Indicator of Central Serotonergic Neurotransmission” in Neuroscience Letters:
“Chronic cannabis use has been found to be associated with major depression. It is suggested that cannabis use induces changes in neurotransmitter systems involved in the pathogenesis of depressive disorders, particularly in the serotonergic system. The analysis of the loudness dependence of auditory evoked potentials (LDAEP) is a valid non-invasive indicator of central serotonergic activity in animals and humans. In the present study, we investigated the effects of chronic cannabis use on LDAEP in 30 psychiatrically unaffected users compared to 30 non-user controls… LDAEP… scores did not differ between cannabis users and controls. Moreover, LDAEP neither correlate with duration and quantity of cannabis use nor with psychometric assessments. These results indicate that chronic cannabis use had no influence on the LDAEP in this study sample. It can be suggested that significant alterations in serotonergic systems may rather be related to acute activation of the endogenous cannabinoid system or to cannabis dependence accompanied by manifest depressive symptoms.

Sep. 2009 – Patrik Roser, PhD, MD

Not Clearly Pro or Con

61.
Human Studies

Feb. 9, 2009
Cancer

Janet R. Daling, PhD, Professor Emeritus of Epidemiology at the University of Washington School of Public Health and member of the Fred Hutchinson Cancer Research Center’s Public Health Sciences Division, et al., wrote the following in their Feb. 9, 2009 article titled “Association of Marijuana Use and the Incidence of Testicular Germ Cell Tumors,” published in Cancer:

“BACKGROUND:
The incidence of testicular germ cell tumors (TGCTs) has been increasing the past 4 to 6 decades; however, exposures that account for this rise have not been identified. Marijuana use also grew during the same period, and it has been established that chronic marijuana use produces adverse effects on the human endocrine and reproductive systems. In this study, the authors tested the hypothesis that marijuana use is a risk factor for TGCT.

METHODS:
A population-based, case-control study of 369 men ages 18 to 44 years who were diagnosed with TGCT from January 1999 through January 2006 was conducted in King, Pierce and Snohomish Counties in Washington State. The responses of these men to questions on their lifetime marijuana use were compared with the responses of 979 age-matched controls who resided in the same 3 counties during the case diagnosis period.

RESULTS:
Men with a TGCT were more likely to be current marijuana smokers at the reference date compared with controls… We observed a 70% increased risk of TGCT associated with current marijuana use, and the risk was particularly elevated for current use that was at least weekly or that began in adolescence. These associations were independent of known TGCT risk factors.”
Feb. 9, 2009 – Janet R. Daling, PhD

Con

60.

Human Studies

2009
British Journal of Psychiatry

Marta Di Forti, MD, MRCPsych, Clinical Lecturer in the Institute of Psychiatry at King’s College London, et al., wrote in their 2009 study “High-potency Cannabis and the Risk of Psychosis” in the British Journal of Psychiatry:

Background: People who use cannabis have an increased risk of psychosis, an effect attributed to the active ingredient ?9-tetrahydrocannabinol (D9-THC). There has recently been concern over an increase in the concentration of D9-THC in the cannabis available in many countries.

Aims: To investigate whether people with a first episode of psychosis were particularly likely to use high-potency cannabis.

Method: We collected information on cannabis use from 280 cases presenting with a first episode of psychosis to the South London & Maudsley National Health Service (NHS) Foundation Trust, and from 174 healthy controls recruited from the local population.

Results: There was no significant difference between cases and controls in whether they had ever taken cannabis, or age at first use. However, those in the cases group were more likely to be current daily users and to have smoked cannabis for more than 5 years. Among those who used cannabis, 78% of the cases group used high-potency cannabis (sinsemilla, ‘ skunk’) compared with 37% of the control group.

Conclusions: The finding that people with a first episode of psychosis had smoked higher-potency cannabis, for longer and with greater frequency, than a healthy control group is consistent with the hypothesis that D9-THC is the active ingredient increasing risk of psychosis. This has important public health implications, given the increased availability and use of high-potency cannabis.”
2009 – Marta Di Forti, MD, MRCPsych

Not Clearly Pro or Con

59.
Human Studies

Sep. 2008
Psychological Medicine

Jim van Os, PhD, MD, Professor of Psychiatry at Maastricht University Medical Centre, et al., wrote in their Sep. 2008 study article “Cannabis Use and Genetic Predisposition for Schizophrenia: A Case-control Study” in Psychological Medicine:

BACKGROUND: Cannabis use may be a risk factor for schizophrenia. Part of this association may be explained by genotype-environment interaction, and part of it by genotype-environment correlation. The latter issue has not been explored. We investigated whether cannabis use is associated with schizophrenia, and whether gene-environment correlation contributes to this association, by examining the prevalence of cannabis use in groups with different levels of genetic predisposition for schizophrenia.

METHOD: Case-control study of first-episode schizophrenia. Cases included all non-Western immigrants who made first contact with a physician for schizophrenia in The Hague, The Netherlands, between October 2000 and July 2005. Two matched control groups were recruited, one among siblings of the cases and one among immigrants who made contact with non-psychiatric secondary health-care services. Conditional logistic regression analyses were used to predict schizophrenia as a function of cannabis use, and cannabis use as a function of genetic predisposition for schizophrenia.

RESULTS: Cases had used cannabis significantly more often than their siblings and general hospital controls (59, 21 and 21% respectively). Cannabis use predicted schizophrenia, but genetic predisposition for schizophrenia did not predict cannabis use.

CONCLUSIONS: Cannabis use was associated with schizophrenia but there was no evidence for genotype-environment correlation.
Sep. 2008 – Jim van Os, PhD, MD

Not Clearly Pro or Con

58.
Human Studies

Mar. 2008
Otolaryngology-Head and Neck Surgery

Richard Beasley, MBChB, DM, FRACP, DSc, Director of the Medical Research Institute of New Zealand, et al., wrote in their Mar. 2008 study “Cannabis Use and Cancer of the Head and Neck: Case-control Study” in Otolaryngology-Head and Neck Surgery:

“Objective: To investigate whether cannabis smoking increases the risk of head and neck cancer.

Results: An increased risk of cancer was found with increasing tobacco use, alcohol consumption, and decreased income but not increasing cannabis use. The highest tertile of cannabis use was associated with a nonsignificant increased risk of cancer after adjustment for confounding variables.

Conclusions: Cannabis use did not increase the risk of head and neck cancer; however, because of the limited power and duration of use studied, a small or longer-term effect cannot be excluded.”
Mar. 2008 – Richard Beasley, MBChB, DM, FRACP, DSc

Not Clearly Pro or Con

57.
Human Studies

Feb. 6, 2008
Journal of the American Medical Association

W. Murray Thomson, PhD, Professor of Dental Epidemiology and Public Health at Sir John Walsh Research Institute, et al., wrote in their Feb. 6, 2008 study “Cannabis Smoking and Periodontal Disease Among Young Adults” in the Journal of the American Medical Association:

“Design and Setting: Prospective cohort study of the general population, with cannabis use determined at ages 18, 21, 26, and 32 years and dental examinations conducted at ages 26 and 32 years. The most recent data collection (at age 32 years) was completed in June 2005.

Participants: A complete birth cohort born in 1972 and 1973 in Dunedin, New Zealand, and assessed periodically (with a 96% follow-up rate of the 1015 participants who survived to age 32 years). Complete data for this analysis were available from 903 participants (comprising 89.0% of the surviving birth cohort).

The study’s demonstration of a strong association between cannabis use and periodontitis experience by age 32 years indicates that long-term smoking of cannabis is detrimental to the periodontal tissues and that public health measures to reduce the prevalence of cannabis smoking may have periodontal benefits for the population. […]

Although definitively establishing the periodontal effects of exposure to cannabis smoke should await confirmation in other populations and settings, health promoters and dental and medical practitioners should take steps to raise awareness of the strong probability that regular cannabis users may be doing damage to the tissues that support their teeth.”
Feb. 6, 2008 – W. Murray Thomson, PhD

Con

56.
Human Studies

2008
The British Journal of Psychiatry

Stanley Zammit, PhD, MB, MA, Clinical Senior Lecturer in the Department of Psychological Medicine and Neurology at Cardiff University, et al., wrote the following in a 2008 article titled “Effects of Cannabis Use on Outcomes of Psychotic Disorders: Systematic Review,” published in The British Journal of Psychiatry:

Background
It is unclear if research findings support clinical opinion that cannabis use leads to worse outcomes in people with psychosis, or whether this impression is confounded by other factors.

Aims
To systematically review the evidence pertaining to whether cannabis affects outcome of psychotic disorders.

Method
We searched 10 relevant databases (to November 2006), reference lists of included studies and contacted experts. We included 13 longitudinal studies from 15 303 references. Data extraction and quality assessment were conducted independently and in duplicate.

Results
Cannabis use was consistently associated with increased relapse and non-adherence. Associations with other outcome measures were more disparate. Few studies adjusted for baseline illness severity, and most made no adjustment for alcohol, or other potentially important confounders. Adjusting for even a few confounders often resulted in substantial attenuation of results.

Conclusions
Confidence that most associations reported were specifically due to cannabis is low. Despite clinical opinion, it remains important to establish whether cannabis is harmful, what outcomes are particularly susceptible, and how such effects are mediated. Studies to examine this further are eminently feasible.

2008 – Stanley Zammit, PhD, MB, MA

Not Clearly Pro or Con

55.

Human Studies

2008
Archives of General Psychiatry

Mikkel Arendt, MScPsych, PhD, Researcher at the Unit for Psychiatric Research of Aalborg Psychiatric Hospital (Denmark), et al., wrote in their 2008 article “Familial Predisposition for Psychiatric Disorder: Comparison of Subjects Treated for Cannabis-Induced Psychosis and Schizophrenia” in the Archives of General Psychiatry:

“The risk of schizophrenia after a cannabis-induced psychosis is independent of familial predisposition… Cannabis-induced psychosis may be an early marker of schizophrenia… Psychotic symptoms after cannabis use should be taken extremely seriously.”
2008 – Mikkel Arendt, MScPsych, PhD

Not Clearly Pro or Con

54.
Human Studies

Dec. 25, 2007
Journal of the National Cancer Institute

Burkhard Hinz, PhD, Director of the Institute of Toxicology and Pharmacology at the University of Rostock in Germany, et al., wrote the following in a Dec. 25, 2007 article titled “Inhibition of Cancer Cell Invasion by Cannabinoids via Increased Expression of Tissue Inhibitor of Matrix Metalloproteinases-1,” published in the Journal of the National Cancer Institute:

“Prior knowledge
Treatment with cannabinoids had been shown to reduce the invasiveness of cancer cells, but the cellular mechanisms underlying this effect were unclear.

Study design
Cancer cells treated with combinations of cannabinoids, antagonists of cannabinoid receptors, and siRNA to tissue inhibitor of matrix metalloproteinases-1 (TIMP-1) were assessed for invasiveness, protein expression, and activation of signal transduction pathways.

Contribution
The expression of TIMP-1 was shown to be stimulated by cannabinoid receptor activation and to mediate the anti-invasive effect of cannabinoids.

Implications
Clarification of the mechanism of cannabinoid action may help investigators to explore their therapeutic benefit.

Limitations
The relevance of the findings to the behavior of tumor cells in vivo remains to be determined.”
Dec. 25, 2007 – Burkhard Hinz, PhD

[Editor’s Note: Although this study was not conducted on humans, it was performed using human cells in a test tube which is why we have classified it under the “Human Studies” category.]

Pro

53.
Human Studies

Aug. 15, 2007
Journal of Acquired Immune Deficiency Syndromes

Margaret Haney, PhD, Associate Professor of Clinical Neuroscience at Columbia University, et al., wrote the following in their Aug. 15, 2007 study titled “Dronabinol and Marijuana in HIV-Positive Marijuana Smokers: Caloric Intake, Mood, and Sleep,” published in the Journal of Acquired Immune Deficiency Syndromes:

“Objectives: This placebo-controlled within-subjects study evaluated marijuana and dronabinol across a range of behaviors: eating topography, mood, cognitive performance, physiologic measures, and sleep.

Methods: HIV-positive marijuana smokers (n = 10) completed 2 16-day inpatient phases. Each dronabinol (5 and 10 mg) and marijuana (2.0% and 3.9% [DELTA]9-tetrahydrocannabinol [THC]) dose was administered 4 times daily for 4 days, but only 1 drug was active per day, thereby maintaining double-blind dosing. Four days of placebo washout separated each active cannabinoid condition.

Results: As compared with placebo, marijuana and dronabinol dose dependently increased daily caloric intake and body weight in HIV-positive marijuana smokers. All cannabinoid conditions produced significant intoxication, except for low-dose dronabinol (5 mg); the intoxication was rated positively (eg, “good drug effect”) with little evidence of discomfort and no impairment of cognitive performance. Effects of marijuana and dronabinol were comparable, except that only marijuana (3.9% THC) improved ratings of sleep.

Conclusions: These data suggest that for HIV-positive marijuana smokers, both dronabinol (at doses 8 times current recommendations) and marijuana were well tolerated and produced substantial and comparable increases in food intake.”
Aug. 15, 2007 – Margaret Haney, PhD

Pro

52.
Human Studies

July 27, 2007
Lancet

Theresa H. M. Moore, MSc, Research Associate in the Department of Social Medicine at the University of Bristol, and Stanley Zammit, PhD, Clinical Lecturer in the Department of Psychological Medicine at Cardiff University, et al., stated the following in their July 27, 2008 article titled “Cannabis Use and Risk of Psychotic or Affective Mental Health Outcomes: A Systematic Review,” published in the Lancet:

“There was an increased risk of any psychotic outcome in individuals who had ever used cannabis… with greater risk in people who used cannabis most frequently. A substantial confounding effect was present for both psychotic and affective outcomes…

The evidence is consistent with the view that cannabis increases risk of psychotic outcomes independently of confounding and transient intoxication effects, although evidence for affective outcomes is less strong. The uncertainty about whether cannabis causes psychosis is unlikely to be resolved by further longitudinal studies such as those reviewed here. However, we conclude that there is now sufficient evidence to warn young people that using cannabis could increase their risk of developing a psychotic illness later in life.”
July 27, 2007 – Theresa Moore, MSc Stanley Zammit, PhD

Con

51.
Human Studies

Feb. 13, 2007
Neurology

Donald Abrams, MD, Professor of Clinical Medicine at the University of California, San Francisco, et al., wrote in their Feb. 13, 2007 article “Cannabis for Treatment of HIV-Related Peripheral Neuropathy” in Neurology:

“Dr. Abrams and the Community Consortium conducted a study to evaluate the safety and effectiveness of smoked marijuana to treat pain caused by HIV-related peripheral neuropathy (injury to the nerves that supply feelings to your arms and feet). The study evaluated whether marijuana had an effect on pain relief. Marijuana was compared to a placebo; a cigarette that smells and tastes like marijuana but has no active ingredients (THC).

The study evaluated both ongoing neuropathic pain (clinical pain) and temporary pain induced by applying heat and capsaicin (ingredient that makes red peppers hot) cream to a small area of the skin (experimental pain).

Fifty-five patients were randomized and 50 completed the entire trial. Smoked marijuana reduced daily pain by 34% compared to 17% with placebo. The study concluded that 52% of patients who smoked marijuana had a greater than 30% reduction in pain compared to 24% in the placebo group. In this study, smoked marijuana was well tolerated and effectively relieved chronic neuropathic pain from HIV-related peripheral neuropathy. The findings are comparable to clinically proven oral drugs for chronic neuropathic pain.”
Feb. 9, 2007 – Donald Abrams, MD

Pro
50.
Human Studies

Feb. 9, 2007
Psychological Medicine

Louisa Degenhardt, PhD, Senior Lecturer at the National Drug and Alcohol Research Centre at the University of New South Wales, et al., wrote in their Feb. 9, 2007 article titled “The Temporal Dynamics of Relationships Between Cannabis, Psychosis and Depression Among Young Adults with Psychotic Disorders: Findings from a 10-month Prospective Study,” in Psychological Medicine:

“Background. The aim was to examine the temporal relationships over 10 months between cannabis use and symptoms of psychosis and depression in people with schizophrenia and related disorders. The design was a prospective study of 101 patients with schizophrenia and related disorders who were assessed monthly over 10 months on medication compliance, cannabis and other drug use, symptoms of depression and symptoms of psychosis.

Method. Linear regression methods to assess relationships between cannabis use and symptoms of psychosis and depression while adjusting for serial dependence, medication compliance and other demographic and clinical variables.

Results. Cannabis use predicted a small but statistically significant increase in symptoms of psychosis, but not depression, after controlling for other differences between cannabis users and non-users. Symptoms of depression and psychosis did not predict cannabis use.

Conclusion. Continued cannabis use by persons with schizophrenia predicts a small increase in psychotic symptom severity but not vice versa.”
Feb. 9, 2007 – Louisa Degenhardt, PhD

Con

49.
Human Studies

Jan. 11, 2007
Schizophrenia Research

Serge Sevy, MD, MBA, Adjunct Associate Professor of Clinical Psychiatry and Behavioral Sciences at the Albert Einstein College of Medicine, et al., wrote in their Jan. 11, 2007 article “Iowa Gambling Task in Schizophrenia: A Review and New Data in Patients with Schizophrenia and Co-occurring Cannabis Use Disorders” in Schizophrenia Research:

“We reviewed previous studies comparing schizophrenia patients and healthy subjects for performance on the Iowa Gambling Task (IGT) (a laboratory task designed to measure emotion-based decision-making), and found mixed results. We hypothesize that deficits in IGT performance in schizophrenia may be more specifically related to concurrent substance use disorders. To test this hypothesis, we compared schizophrenia patients with (SCZ(+)) or without (SCZ(-)) cannabis use disorders, to healthy subjects, on measures of cognition and IGT performance…

There were no differences between SCZ(+) and SCZ(-) patients on most of the cognitive tests, and IGT performance… Schizophrenia patients show widespread impairments in several cognitive domains and emotion-based decision-making… More intriguing, it appears that the concurrent abuse of cannabis has no compounding effects on cognition, as well as emotion/affect-based decision-making.”
Jan. 11, 2007 – Serge Sevy, MD, MBA

Not Clearly Pro or Con

48.
Human Studies

Sep. 2006
Journal of Psychopharmacology

Antonio W. Zuardi, PhD, Vice Director of the Department of Neurology at the University of São Paulo, et al., wrote in a Sep. 2006 article titled “Cannabidiol Monotherapy for Treatment-Resistant Schizophrenia” in the Journal of Psychopharmacology:

“Cannabidiol (CBD), one of the major products of the marijuana plant, is devoid of marijuana’s typical psychological effects. In contrast, potential antipsychotic efficacy has been suggested based on preclinical and clinical data (Zuardi et al., 2002). In this report, we further investigated the efficacy and safety of CBD monotherapy in three patients with treatment-resistant schizophrenia (TRS)…

Efficacy, tolerability and side effects were assessed. One patient showed mild improvement, but two patients didn’t show any improvement during CBD monotherapy. All patients tolerated CBD very well and no side effects were reported. These preliminary data suggest that CBD monotherapy may not be effective for TRS.”
Sep. 2006 – Antonio W. Zuardi, PhD

Con

47.
Human Studies

Mar. 2005
Addiction

David M. Fergusson, PhD, Research Professor of the Department of Psychological Medicine at the University of Otago, et al., wrote the following in a Mar. 2005 article titled “Tests of Causal Linkages Between Cannabis Use and Psychotic Symptoms,” published in the journal Addiction:

“Regression models adjusting for observed and non-observed confounding suggested that daily users of cannabis had rates of psychotic symptoms that were between 1.6 and 1.8 times higher than non-users of cannabis….

The results of the present study add to a growing body of evidence suggesting that regular cannabis use may increase risks of psychosis.

The present study suggests that:
(a) the association between cannabis use and psychotic symptoms is unlikely to be due to confounding factors; and
(b) the direction of causality is from cannabis use to psychotic symptoms.”
Mar. 2005 – David M. Fergusson, PhD

Con

46.
Human Studies

Mar. 2005
Journal of Psychopharmacology

David M. Semple, MBBS, Consultant Psychiatrist at Hairmyres Hospital, et al., wrote in their Mar. 2005 article “Cannabis as a Risk Factor for Psychosis: Systematic Review,” in the Journal of Psychopharmacology:

“Early use of cannabis did appear to increase the risk of psychosis. For psychotic symptoms, a dose-related effect of cannabis use was seen, with vulnerable groups including individuals who used cannabis during adolescence, those who had previously experienced psychotic symptoms, and those at high genetic risk of developing schizophrenia. In conclusion, the available evidence supports the hypothesis that cannabis is an independent risk factor, both for psychosis and the development of psychotic symptoms. Addressing cannabis use, particularly in vulnerable populations, is likely to have beneficial effects on psychiatric morbidity.”
Mar. 2005 – David M. Semple, MBBS

Con

45.
Human Studies

Feb. 2005
Journal of Neuroscience

Maria L. de Ceballos, PhD, Researcher and Group Leader of the Department of Neural Plasticity at the Cajal Institute, Spain, et al., wrote the following in a Feb. 2005 article titled “Prevention of Alzheimer’s Disease Pathology by Cannabinoids: Neuroprotection Mediated by Blockage of Microglial Activation,” published in the Journal of Neuroscience:

“Our results indicate that cannabinoid receptors are important in the pathology of AD [Alzheimer’s Disease] and that cannabinoids succeed in preventing the neurodegenerative process occurring in the disease.”
Feb. 2005 – Maria L. de Ceballos, PhD

Pro

44.
Human Studies

Jan. 2005
Psychiatry Research

Jason Schiffman, PhD, Associate Professor of Clinical Psychology at the University of Hawaii at Manoa, et al., wrote the following in their Jan. 2005 article titled “Symptoms of Schizotypy Precede Cannabis Use,” published in the journal Psychiatric Research:

“Findings suggest that regular cannabis users are significantly more prone to cognitive and perceptual distortions as well as disorganization, but not interpersonal deficits, than non-regular users and those who have never used.

Additionally, the onset of schizotypal symptoms generally precedes the onset of cannabis use. The findings do not support a causal link between cannabis use and schizotypal traits.”
Jan. 2005 – Jason Schiffman, PhD

Not Clearly Pro or Con

43.

Human Studies

2005
Journal of the International Association for Cannabis as Medicine

Donald Abrams, MD, Professor of Clinical Medicine at the University of California, San Francisco, et al., wrote in their 2005 meeting abstract “Smoked Cannabis Therapy for HIV-related Painful Peripheral Neuropathy: Results of a Randomized, Placebo-controlled Clinical Trial,” published in the Journal of the International Association for Cannabis as Medicine:

“Smoked marijuana is effective in reducing chronic ongoing neuropathic pain as well as acute pain in the experimental pain model. The magnitude of the response of the neuropathic pain is similar to what is seen with gabapentin, a widely used therapeutic intervention for HIV neuropathy.”
2005 – Donald Abrams, MD

Pro

42.

Human Studies

Dec. 1, 2004
British Medical Journal

Cécile Henquet, PhD, Researcher in the Department of Psychiatry and Neuropsychology at Maastricht University, et al., wrote in their Dec. 1, 2004 article “Prospective Cohort Study of Cannabis Use, Predisposition for Psychosis, and Psychotic Symptoms in Young People” in the British Medical Journal:

“After adjustment for age, sex, socioeconomic status, urbanicity, childhood trauma, predisposition for psychosis at baseline, and use of other drugs, tobacco, and alcohol, cannabis use at baseline increased the cumulative incidence of psychotic symptoms at follow up four years later. The effect of cannabis use was much stronger in those with any predisposition for psychosis at baseline than in those without. The risk difference in the ‘predisposition’ group was significantly greater than the risk difference in the ‘no predisposition’ group. There was a dose-response relation with increasing frequency of cannabis use. Predisposition for psychosis at baseline did not significantly predict cannabis use four years later…

Cannabis use moderately increases the risk of psychotic symptoms in young people but has a much stronger effect in those with evidence of predisposition for psychosis.
Dec. 1, 2004 – Cécile Henquet, PhD

Con
41.
Human Studies

Oct. 21, 2004
Schizophrenia Research

John Stirling, DPhil, Principal Lecturer/Reader in the Research Institute for Health and Social Change at Manchester Metropolitan University, et al., wrote in their Oct. 21, 2004 article “Cannabis Use Prior to First Onset Psychosis Predicts Spared Neurocognition at 10-year Follow-up” in Schizophrenia Research:

“A priori cannabis use was recorded at index admission for 112 participants in the Manchester first-episode psychosis cohort. 69 of the 100 surviving (mainly schizophrenia) patients were followed up 10–12 years later and assessed on a battery of clinical, behavioural and neurocognitive measures. Individuals who had not used cannabis before the first episode of illness were generally indistinguishable from cannabis users at follow-up, except that the latter group evidenced a marked ‘sparing’ of neurocognitive functions…

“[C]annabis users had better cognitive functioning than patients without cannabis use in several domains including design memory, verbal fluency, object assembly, block design, picture completion, picture arrangement, and face recognition memory.”
Oct. 21, 2004 – John Stirling, DPhil

Pro

40.
Human Studies

Sep. 2004
Movement Disorders

Researchers from the Movement Disorders Centre, Department of Neurology at Charles University, Prague, Czech Republic, wrote in their Sep. 2004 article “Survey on Cannabis Use in Parkinson’s Disease,” published in the journal Movement Disorders:

“An anonymous questionnaire sent to all patients attending the Prague Movement Disorder Centre revealed that 25% of 339 respondents had taken cannabis and 45.9% of these described some form of benefit….

The late onset of cannabis action is noteworthy. Because most patients reported that improvement occurred approximately two months after the first use of cannabis, it is very unlikely that it could be attributed to a placebo reaction.”
Sep. 2004 – Movement Disorders

Pro

39.
Human Studies

Aug. 2004
Multiple Sclerosis

Ciaran M. Brady, Specialist Registrar in Urology at Edith Cavell Hospital, et al., wrote the following in an Aug. 2004 article titled “An Open-Label Pilot Study of Cannabis-based Extracts for Bladder Dysfunction in Advanced Multiple Sclerosis,” published in the journal Multiple Sclerosis:

“The majority of patients with multiple sclerosis (MS) develop troublesome lower urinary tract symptoms (LUTS). Anecdotal reports suggest that cannabis may alleviate LUTS, and cannabinoid receptors in the bladder and nervous system are potential pharmacological targets. In an open trial we evaluated the safety, tolerability, dose range, and efficacy of two whole-plant extracts of Cannabis sativa in patients with advanced MS and refractory LUTS.”

“Urinary urgency, the number and volume of incontinence episodes, frequency and nocturia all decreased significantly following treatment (P <0.05, Wilcoxon’s signed rank test). However, daily total voided, catheterized and urinary incontinence pad weights also decreased significantly on both extracts. Patient self-assessment of pain, spasticity and quality of sleep improved significantly (P <0.05, Wilcoxon’s signed rank test) with pain improvement continuing up to median of 35 weeks.There were few troublesome side effects, suggesting that cannabis-based medicinal extracts are a safe and effective treatment for urinary and other problems in patients with advanced MS.”
Aug. 2004 – Ciaran M. Brady

Pro

38.
Human Studies

July 2004
Accident Analysis & Prevention

K. L. L. Movig, et al., wrote the following in their article titled “Psychoactive Substance Use and the Risk of Motor Vehicle Accidents,” published in the journal Accident Analysis & Prevention:

“The objective of this study was to estimate the association between psychoactive drug use and motor vehicle accidents requiring hospitalization…

The risk for road trauma was increased for single use of benzodiazepines and alcohol… High relative risks were estimated for drivers using combinations of drugs and those using a combination of drugs and alcohol. Increased risks, although not statistically significant, were assessed for drivers using amphetamines, cocaine, or opiates.

No increased risk for road trauma was found for drivers exposed to cannabis.”
July 2004 – Accident Analysis & Prevention

Not Clearly Pro or Con

37.
Human Studies

May 15, 2004
Lancet

John Macleod, PhD, MSc, Senior Lecturer in Primary Care in the Department of Primary Care and General Practice at the University of Birmingham, et al., wrote the following in their article “Psychological and Social Sequelae of Cannabis and Other Illicit Drug Use by Young People: A Systematic Review of Longitudinal, General Population Studies,” published May 15, 2004 in the Lancet:

“Available evidence does not strongly support an important causal relation between cannabis use by young people and psychosocial harm, but cannot exclude the possibility that such a relation exists.

The lack of evidence of robust causal relations prevents the attribution of public health detriments to illicit drug use. In view of the extent of illicit drug use, better evidence is needed.”
May 15, 2004 – John Macleod, PhD

Not Clearly Pro or Con

36.
Human Studies

May 2004
Journal of the American Medical Association

Wilson M. Compton, MD, et al., wrote the following in their May 2004 article “Prevalence of Marijuana Use Disorders in the United States: 1991-1992 and 2001-2002,” published in the Journal of the American Medical Association (JAMA):

“Among the adult U.S. population, the prevalence of marijuana use remained stable at about 4.0% over the past decade. In contrast, the prevalence of DSM-IV [psychological classifications of disorders] marijuana abuse or dependence significantly increased between 1991-1992 and 2001-2002, with the greatest increases observed among young black men and women and young Hispanic men.

Further, marijuana use disorders among marijuana users significantly increased in the absence of increased frequency and quantity of marijuana use, suggesting that the concomitant increase in potency of delta-9-THC [one of the active ingredients in marijuana] may have contributed to the rising rates…

[M]arijuana abuse or dependence increased among marijuana users by 18% from 30.2% in 1991-1992 to 35.6% in 2001-2002…

The potency of delta-9-THC in confiscated marijuana from police seizure increased by 66% from 3.08% in 1992 to 5.11% in 2002…

Moreover, there was no systematic change in the frequency of marijuana use between 1991-1992 and 2001-2001…

Increasing rates of marijuana use disorders among marijuana users in the absence of increased quantity and frequency of use strengthens the argument that the increasing rates may be attributable, in part, to increased potency of marijuana.”
May 2004 – Journal of the American Medical Association

Not Clearly Pro or Con

35.
Human Studies

May 2004
American Journal of Public Health

Craig Reinarman, PhD, et al., in their research study “The Limited Relevance of Drug Policy: Cannabis in Amsterdam and in San Francisco,” published in the May 2004 issue of theAmerican Journal of Public Health(AJPH), wrote:

“Results: With the exception of higher drug use in San Francisco, we found strong similarities across both cities. We found no evidence to support claims that criminalization reduces use or that decriminalization increases use.

Conclusions: Drug policies may have less impact on cannabis use than is currently thought.”
May 2004 – American Journal of Public Health

Not Clearly Pro or Con

34.
Human Studies

Jan. 2004
Journal of Acquired Immune Deficiency Syndromes

Diane Prentiss, MA, MPH, et al., wrote the following in their article titled “Patterns of Marijuana Use Among Patients with HIV/AIDS Followed in a Public Health Care Setting,” published in the Jan. 2004 issue of Journal of Acquired Immune Deficiency Syndromes (JAIDS):

“Objectives: To examine prevalence and patterns of smoked marijuana and perceived benefit and to assess demographic and clinical factors associated with marijuana use among HIV patients in a public health care setting…

Results: Overall prevalence of smoked marijuana in the previous month was 23%. Reported benefits included relief of anxiety and/or depression (57%), improved appetite (53%), increased pleasure (33%), and relief of pain (28%). Recent use of marijuana was positively associated with severe nausea and recent use of alcohol and negatively associated with being Latino.

Conclusions: The findings suggest that providers be advised to assess routinely and better understand patients’ indications for self-administration of cannabis. Given the estimated prevalence, more formal characterization of the patterns and impact of cannabis use to alleviate HIV-associated symptoms is warranted. Clinical trials of smoked and noncombustible marijuana are needed to determine the role of cannabinoids as a class of agents with potential to improve quality of life and health care outcomes among patients with HIV/AIDS.”
Jan. 2004 – Journal of Acquired Immune Deficiency Syndromes

Not Clearly Pro or Con

33.
Human Studies

Nov. 2003
Lancet

John P. Zajicek, PhD, Professor of Clinical Neuroscience at the Neurology Research and Clinical Trials Unit of the Peninsula Medical School at the University of Plymouth, et al., wrote the following in a Nov.2003 article titled “Cannabinoids for Treatment of Spasticity and Other Symptoms Related to Multiple Sclerosis (CAMS study): Multicentre Randomised Placebo-controlled Trial” in the journal Lancet:

“Background: Multiple sclerosis is associated with muscle stiffness, spasms, pain, and tremor. Much anecdotal evidence suggests that cannabinoids could help these symptoms. Our aim was to test the notion that cannabinoids have a beneficial effect on spasticity and other symptoms related to multiple sclerosis…

Interpretation: Treatment with cannabinoids did not have a beneficial effect on spasticity when assessed with the Ashworth scale. However, though there was a degree of unmasking among the patients in the active treatment groups, objective improvement in mobility and patients’ opinion of an improvement in pain suggest cannabinoids might be clinically useful.”
Nov. 2003 – John P. Zajicek, PhD

Not Clearly Pro or Con

32.
Human Studies

Oct. 2003
Nature Reviews – Cancer

An Oct. 2003 article in Nature Reviews – Cancer, “Cannabinoids: Potential Anticancer Agents,” by Manuel Guzman, PhD, reported:

“Cannabinoids — the active components of Cannabis sativaand their derivatives — exert palliative effects in cancer patients by preventing nausea, vomiting and pain and by stimulating appetite.

In addition, these compounds have been shown to inhibit the growth of tumour cells in culture and animal models by modulating key cell-signaling pathways.

Cannabinoids are usually well tolerated, and do not produce the generalized toxic effects of conventional chemotherapies.”
Oct. 2003 – Nature Reviews – Cancer

Pro

31.
Human Studies

Aug. 2003
Annals of Internal Medicine

Donald Abrams, MD, Professor of Clinical Medicine at the University of California, San Francisco, et al., wrote the following in their article “Short-term Effects of Cannabinoids in Patients with HIV-1 Infection: A Randomized, Placebo-controlled Clinical Trial,” published Aug. 2003 in the journal Annals of Internal Medicine:

“Conclusions: Smoked and oral cannabinoids [marijuana] did not seem to be unsafe in people with HIV infection with respect to HIV RNA levels, CD4 and CD8 cell counts, or protease inhibitor levels over a 21-day treatment.”

The accompanying “Summaries For Patients (35 KB) provided by the journal stated:

“Patients receiving cannabinoids [smoked marijuana and marijuana pills] had improved immune function compared with those receiving placebo. They also gained about 4 pounds more on average than those patients receiving placebo.”
Aug. 2003 – Donald Abrams, MD

Pro

30.
Human Studies

Mar. 2003
Pain

Mark A. Ware, MSc, Director of Research at the Magill University Health Centre (MUHC) Pain Clinic in Canada, et al., wrote the following in a Mar. 2003 article titled “Cannabis Use for Chronic Non-Cancer Pain: Results of a Prospective Survey” in the journal Pain:

“There has been a surge in interest in medicinal cannabis in Canada. We conducted a questionnaire survey to determine the current prevalence of medicinal cannabis use among patients with chronic non-cancer pain, to estimate the dose size and frequency of cannabis use, and to describe the main symptoms for which relief was being sought…

Of the 32 subjects who used cannabis for pain, 17 (53%) used four puffs or less at each dosing interval, eight (25%) smoked a whole cannabis cigarette (joint) and four (12%) smoked more than one joint. Seven (22%) of these subjects used cannabis more than once daily, five (16%) used it daily, eight (25%) used it weekly and nine (28%) used it rarely. Pain, sleep and mood were most frequently reported as improving with cannabis use, and ‘high’ and dry mouth were the most commonly reported side effects. We conclude that cannabis use is prevalent among the chronic non-cancer pain population, for a wide range of symptoms, with considerable variability in the amounts used.”
Mar. 2003 – Mark A. Ware, MSc

Pro

29.
Human Studies

Feb. 11, 2003
Drug and Alcohol Dependence

Louisa Degenhardt, PhD, Senior Lecturer at the National Drug and Alcohol Research Centre at the University of New South Wales, et al., wrote in their Feb. 11, 2003 article “Testing Hypotheses About the Relationship Between Cannabis Use and Psychosis” in Drug and Alcohol Dependence:

“There was a steep rise in the prevalence of cannabis use in Australia over the past 30 years and a corresponding decrease in the age of initiation of cannabis use. There was no evidence of a significant increase in the incidence of schizophrenia over the past 30 years. Data on trends the age of onset of schizophrenia did not show a clear pattern. Cannabis use among persons with schizophrenia has consistently been found to be more common than in the general population.”
Feb. 11, 2003 – Louisa Degenhardt, PhD

Pro

28.
Human Studies

Feb. 2003
British Journal of Psychiatry

In a Feb. 2003 article published in the British Journal of Psychiatry (BJP) titled “Adolescent Precursors of Cannabis Dependence: Findings from the Victorian Adolescent Health Cohort,” which studied students in Australia from 1992 through 1998 (when they were 20-21 years old), researchers noted the following:

“Results Of 1,601 young adults, 115 met criteria for cannabis dependence. Male gender, regular cannabis use and persistent cigarette smoking independently predicted cannabis dependence. Neither smoking severity nor persistent psychiatric morbidity independently predicted dependence. Regular cannabis use increased risk only in the absence of persistent problematic alcohol use.

Conclusions Weekly cannabis use marks a threshold for increased risk of later dependence, with selection of cannabis in preference to alcohol possibly indicating an early addiction process.”
Feb. 2003 – British Journal of Psychiatry

Not Clearly Pro or Con

27.
Human Studies

Jan. 2003
Journal of the American Medical Association

A study of 311 young adult twin pairs conducted by Michael T. Lynskey, PhD published Jan. 2003 in the Journal of the American Medical Association (JAMA) reported:

“Results: Individuals who used cannabis by age 17 years had odds of other drug use, alcohol dependence, and drug abuse/dependence that were 2.1 to 5.2 times higher than those of their co-twin, who did not use cannabis before age 17 years…

In particular, early access to and use of cannabis may reduce perceived barriers against the use of other illegal drugs and provide access to these drugs.”
Jan. 2003 – Journal of the American Medical Association

Not Clearly Pro or Con

26.
Human Studies

Jan. 2003
Psychological Medicine

David M. Fergusson, PhD, Research Professor in the Department of Psychological Medicine at the Christchurch School of Medicine and Health Sciences at the University of Otago, et al., wrote in their Jan. 2003 article “Cannabis Dependence and Psychotic Symptoms in Young People,” in Psychological Medicine:

BACKGROUND: The aims of this research were to use data gathered over the course of a 21 year longitudinal study to examine the linkages between cannabis dependence at ages 18 and 21 and rates of psychotic symptoms taking into account previous symptom levels and other confounding factors.

METHOD: Data were gathered during the course of the Christchurch Health and Development Study (CHDS). The CHDS is a longitudinal study of a birth cohort of 1,265 children who have been studied from birth to age 21. As part of this study, data were gathered on cannabis dependence and psychotic symptoms at ages 18 and 21.

RESULTS: Young people meeting DSM-IV criteria for cannabis dependence had elevated rates of psychotic symptoms at ages 18… These associations were adjusted for previous psychotic symptoms and a range of other confounding factors using a generalized estimating equation model. This analysis showed that after adjustment for confounding factors, those meeting criteria for cannabis dependence still had an increased rate of psychotic symptoms.

CONCLUSIONS: The results show that the development of cannabis dependence is associated with increased rates of psychotic symptoms in young people even when pre-existing symptoms and other background factors are taken into account.
Jan. 2003 – David M. Ferguson, PhD

Con

25.
Human Studies

Nov. 23, 2002
British Medical Journal

Stanley Zammit, PhD, Clinical Lecturer in the Department of Psychological Medicine at Cardiff University, and Peter Allebeck, MD, Professor of Social Medicine in the Department of Public Health Sciences at the Karolinska Institutet, wrote the following in their Nov. 23, 2002 article “Self Reported Cannabis Use as a Risk Factor for Schizophrenia in Swedish Conscripts of 1969: Historical Cohort Study,” in the British Medical Journal:

“Cannabis was associated with an increased risk of developing schizophrenia in a dose dependent fashion both for subjects who had ever used cannabis… and for subjects who had used only cannabis and no other drugs.

Conclusions
Cannabis use is associated with an increased risk of developing schizophrenia, consistent with a causal relation. This association is not explained by use of other psychoactive drugs or personality traits relating to social integration.”
Nov. 23, 2002 – Stanley Zammit, PhD Peter Allebeck, MD

Con

24.
Human Studies

Nov. 23, 2002
British Medical Journal

Terrie E. Moffitt, PhD, Professor, Social Behaviour and Development, Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, King’s College London, et al., wrote the following in their Nov. 23, 2002 article “Cannabis Use in Adolescence and Risk for Adult Psychosis: Longitudinal Prospective Study,” in the British Medical Journal:

“Using cannabis in adolescence increases the likelihood of experiencing symptoms of schizophrenia in adulthood. Our findings… add three new pieces of evidence. Firstly, cannabis use is associated with an increased risk of experiencing schizophrenia symptoms, even after psychotic symptoms preceding the onset of cannabis use are controlled for, indicating that cannabis use is not secondary to a pre-existing psychosis. Secondly, early cannabis use (by age 15) confers greater risk for schizophrenia outcomes than later cannabis use (by age 18). The youngest cannabis users may be most at risk because their cannabis use becomes longstanding. Thirdly, risk was specific to cannabis use, as opposed to use of other drugs, and early cannabis use did not predict later depression. Our findings now require replication in large population studies with detailed measures of cannabis use and schizophrenia.

Although most young people use cannabis in adolescence without harm, a vulnerable minority experience harmful outcomes. A tenth of the cannabis users by age 15 in our sample (3/29) developed schizophreniform disorder by age 26 compared with 3% of the remaining cohort (22/730). Our findings suggest that cannabis use among psychologically vulnerable adolescents should be strongly discouraged by parents, teachers, and health practitioners. Policy makers and law makers should concentrate on delaying onset of cannabis use.
Nov. 23, 2002 – Terrie E. Moffitt, PhD

Con
23.
Human Studies

Sep. 2002
Addiction

A Sep. 2002 article in the journal Addiction, “Cannabis Use and Psychosocial Adjustment in Adolescence and Young Adulthood,” stated:

“Cannabis use, and particularly regular or heavy use, was associated with increased rates of a range of adjustment problems in adolescence / young adulthood — other illicit drug use, crime, depression and suicidal behaviours — with these adverse effects being most evident for schoolaged regular users.

The findings reinforce public health concerns about minimizing the use of cannabis among school-aged populations.”
Sep. 2002 – Addiction

Not Clearly Pro or Con

22.
Human Studies

Apr. 17, 2002
American Journal of Epidemiology

Jim van Os, PhD, MD, Professor of Psychiatric Epidemiology at Maastricht University Medical Centre (Netherlands), et al., wrote in their Apr. 17, 2002 article “Cannabis Use and Psychosis: A Longitudinal Population-based Study,” in the American Journal of Epidemiology:

“Cannabis use may increase the risk of psychotic disorders and result in a poor prognosis for those with an established vulnerability to psychosis. A 3-year follow-up (1997–1999) is reported of a general population of 4,045 psychosis-free persons and of 59 subjects in the Netherlands with a baseline diagnosis of psychotic disorder. Substance use was assessed at baseline, 1-year follow-up, and 3-year follow-up… The effect of baseline cannabis use was stronger than the effect at 1-year and 3-year follow-up, and more than 50% of the psychosis diagnoses could be attributed to cannabis use. On the additive scale, the effect of cannabis use was much stronger in those with a baseline diagnosis of psychotic disorder… than in those without… Results confirm previous suggestions that cannabis use increases the risk of both the incidence of psychosis in psychosis-free persons and a poor prognosis for those with an established vulnerability to psychotic disorder.”
Apr. 17, 2002 – Jim van Os, PhD, MD

Con

21.
Human Studies

Jan. 2002
Journal of Cannabis Therapeutics

Ethan Russo, MD, Senior Medical Advisor at the Cannabinoid Research Institute, et al., stated in his study of four of the remaining seven legal Medical Marijuana patients, titled “Chronic Cannabis Use in the Compassionate Investigational New Drug Program: An Examination of Benefits and Adverse Effects of Legal Clinical Cannabis,” (376 KB) and published in the Jan. 2002 edition of the Journal of Cannabis Therapeutics (JCT):

“The aim of this study is to examine the overall health status of 4 of the 7 surviving patients in the [Compassionate IND] program. This project provides the first opportunity to scrutinize the long-term effects of cannabis on patients who have used a known dosage of a standardized, heat-sterilized quality-controlled supply of low-grade marijuana for 11 to 27 years.

Results demonstrate clinical effectiveness in these patients in treating glaucoma, chronic musculoskeletal pain, spasm and nausea, and spasticity of multiple sclerosis. All 4 patients are stable with respect to their chronic conditions, and are taking many fewer standard pharmaceuticals than previously.

Mild changes in pulmonary function were observed in 2 patients, while no functionally significant attributable sequelae were noted in any other physiological system examined in the study, which included: MRI scans of the brain, pulmonary function tests, chest X-ray, neuropsychological tests, hormone and immunological assays, electroencephalography, P300 testing, history, and neurological clinical examination.

These results would support the provision of clinical cannabis to a greater number of patients in need. We believe that cannabis can be a safe and effective medicine with various suggested improvements in the existing Compassionate IND program.”
Jan. 2002 – Ethan Russo, MD

Pro

20.
Human Studies

Dec. 2001
American Journal of Psychiatry

Gregory Bovasso, PhD, Assistant Professor of Behavioral Sciences at the Community College of Philadelphia, wrote the following in his Dec. 2001 study titled “Cannabis Abuse as a Risk Factor for Depressive Symptoms,” published in the American Journal of Psychiatry:

“Participants (N=1,920) in the 1980 Baltimore Epidemiologic Catchment Area (ECA) study who were reassessed between 1994 and 1996 as part of a follow-up study…

RESULTS: In participants with no baseline depressive symptoms, those with a diagnosis of cannabis abuse at baseline were four times more likely than those with no cannabis abuse diagnosis to have depressive symptoms at the follow-up assessment… In particular, these participants were more likely to have experienced suicidal ideation and anhedonia [inability to experience pleasure in normally pleasurable acts] during the follow-up period.
Dec. 2001 – Gregory Bovasso, PhD

Con

19.
Human Studies

Nov. 2001
International Journal of Drug Policy

Lester Grinspoon, MD, Professor of Psychiatry at the Harvard Medical School, wrote in an article published in Nov. 2001 in the International Journal of Drug Policy:

“The cannabinoids in whole marijuana can be separated from the burnt plant products by devices already being perfected that will be inexpensive when manufactured in large numbers.

Inhalation is a highly effective means of delivery, and faster means will not be available for analogs (except in a few situations such as parenteral injection in an unconscious patient or one with pulmonary impairment). Furthermore, any new analog will have to have an acceptable therapeutic ratio.

The therapeutic ratio of marijuana is not known because it has never caused an overdose death, but it is estimated on the basis of extrapolation from animal data to be 20,000 to 40,000. The therapeutic ratio of a new analog is unlikely to be higher than that; in fact, it may be less safe because it will be physically possible to ingest more.”
Nov. 2001 – Lester Grinspoon, MD

Pro

18.
Human Studies

Oct. 2001
Archives of General Psychiatry

In a study of “Marijuana Abstinence Effects in Marijuana Smokers Maintained in Their Home Environment,” conducted through the University of Vermont, Burlington and the U.S. Air Force, Biomedical Science Corps, and published in the Oct. 2001 issue of the Archives of General Psychiatry (AGP), researchers concluded:

“This study validated several specific effects of marijuana abstinence in heavy marijuana users, and showed they were reliable and clinically significant.

These withdrawal effects appear similar in type and magnitude to those observed in studies of nicotine withdrawal.”

Researchers additionally noted the following specifics regarding “withdrawal discomfort,” which they stated “increased significantly during the abstinence phases and returned to baseline” when marijuana smoking resumed:

“Craving for marijuana, decreased appetite, sleep difficulty, and weight loss reliably changed across the smoking and abstinence phases. Aggression, anger, irritability, restlessness, and strange dreams increased significantly during one abstinence phase, but not the other.”
Oct. 2001 – Archives of General Psychiatry

Not Clearly Pro or Con

17.
Human Studies

July 2001
Pharmacology, Biochemistry and Behavior

Anna H. Soderpalm, PhD, Post-doctoral Fellow in the Department of Psychiatry at the University of Chicago, et al., wrote in a July 2001 article titled “Antiemetic Efficacy of Smoked Marijuana: Subjective and Behavioral Effects on Nausea Induced by Syrup of Ipecac” in the journal Pharmacology, Biochemistry and Behavior:

“Although the public debate about the legalization of marijuana has continued for as long as 25 years, few controlled studies have been conducted to assess its potential medical benefits. The present study examined the antiemetic effect of smoked marijuana cigarettes (8.4 and 16.9 mg Delta(9)-tetrahydrocannabinol [THC]) compared to a highly potent antiemetic drug, ondansetron (8 mg) in 13 healthy volunteers. Nausea and emesis were induced by syrup of ipecac.

Marijuana significantly reduced ratings of ‘queasiness’ and slightly reduced the incidence of vomiting compared to placebo. Ondansetron completely eliminated the emetic effects of ipecac. These findings support and extend previous results, indicating that smoked marijuana reduces feelings of nausea and also reduces emesis in this model. However, its effects are very modest relative to ondansetron, and the psychoactive effects of marijuana are likely to limit its clinical usefulness in the general population.”
July 2001 – Anna H. Soderpalm, PhD

Pro

16.
Human Studies

June 2001
Journal of Cannabis Therapeutics

Donald P. Tashkin, MD, Director of the Pulmonary Function Laboratories at UCLA, in his article “Effects of Smoked Marijuana on the Lung and Its Immune Defenses: Implications for Medicinal Use in HIV-Infected Patients” published in the Journal of Cannabis Therapeutics (JCT), stated:

“Frequent marijuana use can cause airway injury, lung inflammation and impaired pulmonary defense against infection. The major potential pulmonary consequences of habitual marijuana use of particular relevance to patients with AIDS is superimposed pulmonary infection, which could be life threatening in the seriously immonocompromised patient.

In view of the immonosuppressive effect of THC, the possibility that regular marijuana use could enhance progression of HIV infection itself needs to be considered, although this possibility remains unexplored to date.”
June 2001 – Donald P. Tashkin, MD

Con

15.
Human Studies

June 2001
Journal of Cannabis Therapeutics

Guy A. Cabral, PhD, in his article “Marijuana and Cannabinoids: Effects on Infections, Immunity, and AIDS”; published in the Journal of Cannabis Therapeutics (JCT), stated:

“The cumulative data obtained through cell culture studies using various immune cell populations extracted from animals or humans, together with those obtained using animal models of infection, are consistent with the proposition that marijuana and cannabinoids alter immune cell function and can exert deleterious effects on resistance to infection in humans….

However, few controlled longitudinal epidemiological and immunological studies have been undertaken to correlate the immunosuppressive effects of marijuana smoke or cannabinoids on the incidence of infections or viral disease in humans.

Clearly, additional investigation to resolve the long-term immunological consequences of cannabinoid and marijuana use as they relate to resistance to infections in humans is warranted.”
June 2001 – Journal of Cannabis Therapeutics

Not Clearly Pro or Con

14.
Human Studies

Apr. 2001
Nature

In a study published in the journalNature (“Physiology: A Hunger for Cannabinoids”) researchers Raphael Mechoulam et al. found:

“[M]olecules found naturally in the body, as well as in cannabis — stimulate appetite.”
Apr. 2001 – Nature

Pro

13.
Human Studies

Mar. 2001
American Journal of Respiratory Cell and Molecular Biology

An article in the Mar. 2001 issue of the American Journal of Respiratory Cell and Molecular Biology (JRCMB), stated:

“Marijuana tar induced higher levels of CYP1A1 messenger RNA (mRNA) than did tobacco tar, yet resulted in much lower CYP1A1 enzyme activity. These differences between marijuana and tobacco were primarily due to Delta-9-tetrahydrocannabinol….

This complex regulation of CYP1A1 by marijuana smoke and the Delta-9-THC that it contains has implications for the role of marijuana as a cancer risk factor.”
Mar. 2001 – American Journal of Respiratory Cell and Molecular Biology

Con

12.
Human Studies

Feb. 2001
British Journal of Psychiatry

Andrew Johns, MB, Senior Lecturer and Consultant Psychiatrist in Forensic Psychiatry at the Maudsley Hospital in London, wrote the following in his article “Psychiatric Effects Of Cannabis” published in the Feb. 2001 edition of the British Journal of Psychiatry:

“An appreciable proportion of cannabis users report short-lived adverse effects, including psychotic states following heavy consumption, and regular users are at risk of dependence.

There is good evidence that taking cannabis leads to acute adverse mental effects in a high proportion of regular users. Many of these effects are dose-related, but adverse symptoms may be aggravated by constitutional factors including youthfulness, personality attributes and vulnerability to serious mental illness….

People with major mental illnesses such as schizophrenia are especially vulnerable in that cannabis generally provokes relapse and aggravates existing symptoms.”
Feb. 2001 – Andrew Johns, MB

Con

11.
Human Studies

2001
Journal of Cannabis Therapeutics

Researchers from GW Pharmaceuticals in the UK wrote in a 2001 article published in the Journal of Cannabis Therapeutics (JCT):

“In practice it has been found that extracts of cannabis [processed whole plant compounds] provide greater relief of pain than the equivalent amount of cannabinoid given as a single chemical entity [such as Marinol]….

Some patients with multiple sclerosis who smoke cannabis [marijuana] report relief of spasm and pain after the second or third puff of a cannabis cigarette. This implies very rapid transit to, and absorption into the central nervous system. The time involved is seconds rather than minutes.”
2001 – Journal of Cannabis Therapeutics

 

 

 

 

 

 

 

 

 

 

 

 

Pro

10.
Human Studies

Summer 2000
Journal of Public Health Policy (JPHP)

E. Single, et al., wrote the following in a Summer 2000 article titled “The Impact of Cannabis Decriminalization in Australia and the United States,” published in theJournal of Public Health Policy (JPHP):

“Citizens who live under decriminalization laws consume marijuana at rates less than or comparable to those who live in regions where the possession of marijuana remains a criminal offense.”
2000 – Journal of Public Health Policy

Not Clearly Pro or Con

9.
Human Studies

2000
Journal of Forensic Sciences

Mahmoud A. ElSohly, PhD, Research Professor at the Research Institute of Pharmaceutical Sciences at the University of Mississippi, in the Journal of Forensic Sciences article titled “Potency Trends of Delta-9-THC and Other Cannabinoids in Confiscated Marijuana from 1980-1997” wrote:

“The potency (concentration of D9-THC) of marijuana samples rose from less than 1.5% in 1980 to approximately 3.3% in 1983 and 1984, then fluctuated around 3% till 1992. Since 1992, the potency of confiscated marijuana samples has continuously risen, going from 3.1% in 1992 to 4.2% in 1997. The average concentration of D9-THC in all cannabis samples showed a gradual rise from 3% in 1991 to 4.47% in 1997.

Hashish and hash oil, on the other hand, showed no specific potency trends. Other major cannabinoids [cannabidiol (CBD), cannabinol (CBN), and cannabichromene (CBC)] showed no significant change in their concentration over the years.”
2000 – Mahmoud A. ElSohly, PhD

Not Clearly Pro or Con

8.
Human Studies

June 1999
Journal of Respiratory Cell and Molecular Biology

A study published in the June 1999 American Journal of Respiratory Cell and Molecular Biology (JRCMB), stated:

“Marijuana (MJ) smoking produces inflammation, edema, and cell injury in the tracheobronchial080 mucosa of smokers and may be a risk factor for lung cancer….

We conclude that MJ [marijuana] smoke containing Delta-9-THC is a potent source of cellular oxidative stress that could contribute significantly to cell injury and dysfunction in the lungs of smokers.”
June 1999 – American Journal of Respiratory Cell and Molecular Biology

Con

7.
Human Studies

Dec. 1998
Acta Psychiatrica Scandinavica

A study published in the Dec. 1998 journalActa Psychiatrica Scandinavica by researchers Muller-Vahl KR, et al., titled “Cannabinoids: Possible Role in Patho-physiology and Therapy of Gilles De La Tourette Syndrome” stated:

“High densities of cannabinoid receptors were found in the basal ganglia and hippocampus, indicating a putative functional role of cannabinoids in movement and behaviour. Anecdotal reports suggested beneficial effects of marijuana in Tourette’s syndrome (TS).

We therefore interviewed 64 TS patients with regard to use of marijuana and its influence on TS symptomatology. Of 17 patients (27%) who reported prior use of marijuana, 14 subjects (82%) experienced a reduction or complete remission of motor and vocal tics and an amelioration of premonitory urges and obsessive-compulsive symptoms.

Our results provide more evidence that marijuana improves tics and behavioural disorders in TS. It can be speculated that cannabinoids might act through specific receptors, and that the cannabinoid system might play a major role in TS pathology.”
Dec. 1998 – Acta Psychiatrica Scandinavica

Pro

6.
Human Studies

Apr. – June 1998
Journal of Psychoactive Drugs

Lester Grinspoon, MD, Professor of Psychiatry at the Harvard Medical School, et al., wrote in an Apr.-June 1998 article titled “The Use of Cannabis as a Mood Stabilizer in Bipolar Disorder: Anecdotal Evidence and the Need for Clinical Research” in the Journal of Psychoactive Drugs:

“The authors present case histories indicating that a number of patients find cannabis (marihuana) useful in the treatment of their bipolar disorder. Some used it to treat mania, depression, or both. They stated that it was more effective than conventional drugs, or helped relieve the side effects of those drugs. One woman found that cannabis curbed her manic rages; she and her husband have worked to make it legally available as a medicine. Others described the use of cannabis as a supplement to lithium (allowing reduced consumption) or for relief of lithium’s side effects. Another case illustrates the fact that medical cannabis users are in danger of arrest, especially when children are encouraged to inform on parents by some drug prevention programs.

An analogy is drawn between the status of cannabis today and that of lithium in the early 1950s, when its effect on mania had been discovered but there were no controlled studies. In the case of cannabis, the law has made such studies almost impossible, and the only available evidence is anecdotal. The potential for cannabis as a treatment for bipolar disorder unfortunately can not be fully explored in the present social circumstances.”
Apr.-June 1998 – Lester Grinspoon, MD

Pro

5.
Human Studies

Feb. 1997
Southern Medical Journal

Richard H. Schwartz, MD, Clinical Professor of Pediatrics at Georgetown University, Eric A. Voth, MD, Chairman of the Institute on Global Drug Policy, et al., wrote the following in their Feb. 1997 article titled “Marijuana to Prevent Nausea and Vomiting in Cancer Patients: A Survey of Clinical Oncologists” in the Southern Medical Journal:

“Marijuana, if rescheduled by the Drug Enforcement Agency, would be the only Food and Drug Administration (FDA)-approved drug to be administered by smoking. American physicians need timely, factual information about probable usage patterns and potential adverse effects of medical marijuana, and a factual complete review of the literature on the subject.

We mailed a survey to 1,500 American clinical oncologists. Of particular interest was whether and how often in the past 24 months these physicians recommended smoked marijuana, synthetic tetrahydrocannabinol, or 5-HT3 (serotonin) antagonists (ondansetron [Zofran], granisetron [Kytril]) for their patients. We also inquired whether and how often the oncologists would prescribe marijuana in the form of cigarettes, were it to be FDA-approved. Completed surveys were received from 1,122 (75%) of the oncologists.

The percentages of oncologists who prescribed or recommended selected antiemetics more than five times between 1992 and 1994 were 98% for 5-HT, antagonists, 6% for dronabinol (Marinol), and 1% for smoked marijuana. We also found that 332 (30%) of the oncologist-respondents to this nationwide survey supported rescheduling of marijuana for medical purposes; however, two thirds (67%) of the 332 respondents who were in favor of rescheduling estimated that they would write less than one prescription per month for marijuana cigarettes. A comprehensive literature review failed to provide persuasive evidence to recommend marijuana as a needed antiemetic medicine.”
Feb. 1997 – Richard H. Schwartz, MD Eric Voth, MD

Con

4.
Human Studies

1997
European Neurology

Paul F. Consroe, PhD, Professor Emeritus in the Department of Pharmacology and Toxicology at the University of Arizona, et al., wrote in a 1997 article titled “The Perceived Effects of Smoked Cannabis on Patients with Multiple Sclerosis” in the journal European Neurology:

“Fifty-three UK and 59 USA people with multiple sclerosis (MS) answered anonymously the first questionnaire on cannabis use and MS. From 97 to 30% of the subjects reported cannabis improved (in descending rank order): spasticity, chronic pain of extremities, acute paroxysmal phenomenon, tremor, emotional dysfunction, anorexia/weight loss, fatigue states, double vision, sexual dysfunction, bowel and bladder dysfunctions, vision dimness, dysfunctions of walking and balance, and memory loss.

The MS subjects surveyed have specific therapeutic reasons for smoking cannabis. The survey findings will aid in the design of a clinical trial of cannabis or cannabinoid administration to MS patients or to other patients with similar signs or symptoms.”
1997 – Paul F. Consroe, PhD

Pro

3.

Human Studies

Nov. 1996
Drug and Alcohol Dependence

Hollie V. Thomas, DPhil, Lecturer in Epidemiology at the University of Wales College of Medicine, wrote in her Nov. 1996 article “A Community Survey of Adverse Effects of Cannabis Use” in Drug and Alcohol Dependence:

“This survey estimates the frequency of various adverse effects of the use of the drug cannabis. A sample of 1000 New Zealanders aged 18-35 years were asked to complete a self-administered questionnaire on cannabis use and associated problems. The questionnaire was derived from criteria for the identification of cannabis abuse which are analagous to criteria commonly used to diagnose alcoholism. Of those who responded 38% admitted to having used cannabis. The most common physical or mental health problems, experienced by 22% of users were acute anxiety or panic attacks following cannabis use. Fifteen percent reported psychotic symptoms following use. Problems related to physical and mental health and control of level of intake were more common than social or relationship problems.”
Nov. 1996 – Hollie V. Thomas, DPhil

Con

2.
Human Studies

Nov. 1993
British Journal of Psychiatry

Hollie V. Thomas, DPhil, Lecturer in Epidemiology at the University of Wales College of Medicine, wrote in his Nov. 1993 article “Psychiatric Symptoms in Cannabis Users” in the British Journal of Psychiatry:

“Cannabis use can lead to a range of short-lived symptoms such as depersonalisation, de-realisation, a feeling of loss of control, fear of dying, irrational panic and paranoid ideas…

The evidence that cannabis has a causative role in chronic psychotic or affective disorders is not convincing, although the drug may modify the course of an already established illness.”
Nov. 1993 – Hollie V. Thomas, DPhil

Not Clearly Pro or Con

1.
Human Studies

July 1991
American Journal of Clinical Oncology

Rick Doblin, PhD, President of the Multidisciplinary Association for Psychedelic Studies (MAPS), and Mark A. R. Kleiman, PhD, Professor of Public Policy at the UCLA School of Public Affairs, wrote in a July 1991 article titled “Marijuana as Antiemetic Medicine: A Survey of Oncologists’ Experiences and Attitudes” in the American Journal of Clinical Oncology:

“A random-sample, anonymous survey of the members of the American Society of Clinical Oncology (ASCO) was conducted in spring 1990 measuring the attitudes and experiences of American oncologists concerning the antiemetic use of marijuana in cancer chemotherapy patients. The survey was mailed to about one third (N = 2,430) of all United States-based ASCO members and yielded a response rate of 43% (1,035).

More than 44% of the respondents report recommending the (illegal) use of marijuana for the control of emesis to at least one cancer chemotherapy patient. Almost one half (48%) would prescribe marijuana to some of their patients if it were legal. As a group, respondents considered smoked marijuana to be somewhat more effective than the legally available oral synthetic dronabinol ([THC] Marinol; Unimed, Somerville, NJ) and roughly as safe. Of the respondents who expressed an opinion, a majority (54%) thought marijuana should be available by prescription.

These results bear on the question of whether marijuana has a “currently accepted medical use,” at issue in an ongoing administrative and legal dispute concerning whether marijuana in smoked form should be available by prescription along with synthetic THC in oral form. This survey demonstrates that oncologists’ experience with the medical use of marijuana is more extensive, and their opinions of it are more favorable, than the regulatory authorities appear to have believed.”
July 1991 – Rick Doblin, PhD Mark A. R. Kleiman, PhD

Pro

III. Animal Studies
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DATE / JOURNAL DESCRIPTION OF STUDY Pro, Con, or Not Clearly Pro or Con for the specific purpose being investigated in the study
4.
Animal Studies

Oct. 2005
Journal of Clinical Investigation

The Oct. 13, 2005 article “Cannabinoids Promote Embryonic and Adult Hippocampus Neurogenesis and Produce Anxiolytic- and Antidepressant-like Effects” by Xia Zhang et al. from the peer-reviewedJournal of Clinical Investigation stated:

“We show that 1 month after chronic HU210 [high-potency cannabinoid] treatment, rats display increased newborn neurons [brain cell growth] in the hippocampal dentate gyrus [a portion of the brain] and significantly reduced measures of anxiety- and depression-like behavior.

Thus, cannabinoids appear to be the only illicit drug whose capacity to produce increased hippocampal newborn neurons is positively correlated with its anxiolytic- and antidepressant-like effects.”
Oct. 2005 – Journal of Clinical Investigation

Pro

3.
Animal Studies

May 2005
Nature Medicine

The article’s abstract (published online: 22 May 2005) from the peer-reviewed journalNature Medicine stated:

“Accelerated osteoclastic bone resorption has a central role in the pathogenesis of osteoporosis and other bone diseases. Identifying the molecular pathways that regulate osteoclast activity provides a key to understanding the causes of these diseases and to the development of new treatments.

Here we show that mice with inactivation of cannabinoid type 1 (CB1) receptors have increased bone mass and are protected from ovariectomy-induced bone loss.

Pharmacological antagonists of CB1 and CB2 receptors prevented ovariectomy-induced bone loss in vivo and caused osteoclast inhibition in vitro by promoting osteoclast apoptosis and inhibiting production of several osteoclast survival factors.

These studies show that the CB1 receptor has a role in the regulation of bone mass and ovariectomy-induced bone loss and that CB1- and CB2-selective cannabinoid receptor antagonists are a new class of osteoclast inhibitors that may be of value in the treatment of osteoporosis and other bone diseases.”
May 2005 – Nature Medicine

Pro

2.
Animal Studies

Sep. 2004
Neuropharmacology

A research study, published in the Sep. 2004 issue of the journalNeuropharmacology reported:

“Gliomas, in particular glioblastoma multiforme or grade IV astrocytoma, are the most frequent class of malignant primary brain tumours and one of the most aggressive forms of cancer. Current therapeutic strategies for the treatment of glioblastoma multiforme are usually ineffective or just palliative.

During the last few years, several studies have shown that cannabinoids — the active components of the plant Cannabis sativa and their derivatives — slow the growth of different types of tumours, including gliomas, in laboratory animals.

Cannabinoids induce apoptosis of glioma cells in culture via sustained ceramide accumulation, extracellular signal-regulated kinase activation and Akt inhibition. In addition, cannabinoid treatment inhibits angiogenesis of gliomas in vivo….

Remarkably, cannabinoids kill glioma cells selectively and can protect non-transformed glial cells from death. These and other findings reviewed here might set the basis for a potential use of cannabinoids in the management of gliomas.”
Sep. 2004 – Neuropharmacology

Pro

1.
Animal Studies

Jan. 2003
Journal of Clinical Investigation

Researchers with the Department of Biochemistry and Molecular Biology, School of Biology, Complutense University, Spain, in a study of the use of cannabis-based ointment on skin tumors, published Jan. 2003 in the Journal of Clinical Investigation (JCI) stated:

“Local administration induced a considerable growth inhibition of malignant tumors generated by inoculation of epidermal tumor cells into nude mice. Cannabinoid-treated tumors showed an increased number of apoptotic cells…

These results support a new therapeutic approach [cannabis-based ointment] for the treatment of skin tumors.”
Jan. 2003 – Journal of Clinical Investigation

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