A recurrent issue in the debate on whether or not to prohibit cannabis is the supposed link between cannabis and insanity, or as the debate evolved, cannabis and psychosis/schizophrenia. Since the 1840s cannabis has been accused of triggering insanity and hailed as a cure for it. With the benefit of hindsight and incalculable scientific research, the verdict is that “[c]annabis is associated with psychosis (a symptom) and schizophrenia (an illness where this symptom is persistent) in complex, contradictory and mysterious ways”.
One of the key psychoactive components of cannabis,tetrahydrocannabinol (THC), might sometimes induce psychosis-like effects, such as anxiety and paranoid delusions, but transient paranoia is not schizophrenia.
Persistent cannabis use (or that of any kind of psychoactive substance) may precipitate psychosis in individuals with genetically pre
disposing factors, and complicate and worsen symptoms in a person with schizophrenia, but there is no evidence it can cause psychosis.
On the other hand, another key component in cannabis, cannabidiol (CBD), has powerful antipsychotic and anti-anxiety properties, so effective that “CBD may be a future therapeutic option in psychosis, in general and in schizophrenia, in particular”.
This might explain why people with schizophrenia or predisposed to psychotic symptoms report relief after using cannabis.
Although the number of users increased and average strength of cannabis has raised significantly, the numbers of people being diagnosed with schizophrenia has remained stable over time.
That is not to say that cannabis is completely harmless, but that the harms are often exaggerated and other environmental factors, such as alcohol for instance, are frequently overlooked. A systematic review of epidemiological data on cannabis dependence (1990-2008) indicates:
the modest increase in risk and the low prevalence of schizophrenia mean that regular cannabis use accounts for only a very small proportion of the disability associated with schizophrenia. From a population health perspective, this raises doubt about the likely impact of preventing cannabis use on the incidence or prevalence of schizophrenia […]
The object here is not to review all the often conflicting evidence on the relation between cannabis and psychosis, but to how one argument, that cannabis causes insanity, prevailed. And this position prevailed despite the lack of evidence to substantiate the claim overriding significant doubts about the relationship that existed from the beginning of the debate. One of the earliest inquiries, by the colonial government of India in 1872, did indeed conclude that habitual ganja use tended to produce insanity, but a careful examination of the evidence presented in the eports underlying that conclusion, shows that the alleged relationship lacked “solid or sound foundations” and its accuracy was often disputed by medical officers.
However, “bad information, administrative expedience and colonial misunderstandings of a complex society” turned into statistics and the statistics provided the “evidence” that cannabis led to mental illness.
The Indian Hemp Drugs Commission in 1894 was also instigated by claims that the lunatic asylums of India were filled with ganja smokers. After extensive research into the nature of asylum statistics the majority of the Commission members agreed “that the effect of hemp drugs in this respect ha[d] hitherto been greatly exaggerated”.
Most medical doctors involved in the study were convinced that cannabis use did not cause insanity, but rather stimulated a mental illnes that “was already lurking in the mind of the individual” and that alcohol played at least an equal if not a more important role.
That conclusion seems to summarize current opinions about the relationship between cannabis and psychosis.
The dramatic announcements on the mental health implications of cannabis use by the Egyptian delegate Mohammed El Guindy at the Geneva conference had a significant impact on the deliberations to include cannabis in the 1925 Convention. El Guindy produced statistics supporting his claims that 30 to 60 per cent cases of insanity were caused by hashish. In a subsequent Memorandum with reference to hashish as it concerns Egypt, submitted by the Egyptian delegation to support El Guindy, the figure was even more alarming, claiming that “about 70 percent of insane people in lunatic asylums in Egypt are hashish eaters or smokers”.
El Guindy’s figures were probably based on the observations of John Warnock, the head of the Egyptian Lunacy Department from 1895 to 1923, published in an article in the Journal of Mental Science in 1924.
However, as historian James Mills showed, Warnock made broad generalizations about cannabis and its users despite that those he saw were only the small proportion of them in hospitals. Whether this was an accurate picture of cannabis use in Egypt did not seem a relevant question to him. Other Egyptian statistics showed a very different picture.
This tendency among some doctors to extrapolate their experiences in mental health departments to society at large was common in many studies in many countries and resulted in ignoring the fact that the vast majority of cannabis users did so without any problem.
Studies often generalised cases of a few single individuals with personality disorders to make broad claims about the overall harmful effects of cannabis.
Not all directors of mental health hospitals reached the same conclusions. The Mexican psychiatrist Leopoldo Salazar Viniegra, for instance, who had earned a reputation as a result of his work with addicts in the national mental health hospital, refuted the existence of a marijuana psychosis. In an article in 1938, entitled El mito de la marihuana (The Myth of Marijuana), he argued that that assumption in public and scientific opinion was based in myth. The link of the substance with insanity, violence and crime, which had dominated the public discourse in Mexico since the 1850s, was the result of sensational media reports and, in later years, U.S. drug enforcement authorities.
According to Salazar, at least in Mexico, alcohol played a much more important role in the onset of psychosis and social problems.
Shortly after he was appointed as head of Mexico’s Federal Narcotics Service, he told U.S. officials that the only way to stem the flow of illicit drugs was through government-controlled distribution. Due to Mexico’s 1920 cannabis prohibition, 80 per cent of the drug law violators were cannabis users. He argued that Mexico should repeal cannabis prohibition to undercut illicit trafficking (the suppression of which he considered impossible in Mexico due to widespread corruption) and focus on the much more serious problems of alcohol and opiates. In 1939, he initiated a programme of clinics dispensing a month’s supply of opiates to addicts through a state monopoly.
Salazar argued that the traditional perceptions of addicts and addiction had to be revised, including “the concept of the addict as a blameworthy, antisocial individual”.
In doing so, Salazar not only made an enemy out of the powerful U.S. Commissioner of Narcotics Anslinger, who had used the alleged relation to push through the prohibitive Marijuana Tax Act, but also went against the opinions of the established medical opinion in Mexico.
As a delegate to the Advisory Committee of the League of Nations and participating in its meeting in Geneva in May 1939, he saw that the intolerance of and demands for prohibiting cannabis had increased exponentially under the leadership of the American delegates and their allies.
He infuriated Anslinger with his proposal to treat addicts in and out of prison with a morphine step-down project.
Back home, in an article in the Gaceta Medica de México, he challenged the validity of the data relating hashish to schizophrenia in a report from Turkey submitted to the Committee.
Salazar considered the then existing international drug control conventions “as practically without effect”.
His opinions opposed Washington’s punitive supply-side approach on drug control and he stepped on too many toes both nationally and internationally. The U.S. consul general in Mexico suggested that ridicule would be the best way to stop the “dangerous theories” of Salazar.
After a concerted campaign in which U.S. and Mexican officials set out to destroy him personally, the Mexican press depicted him as a madman and “propagandist for marijuana”.
Due to the intense diplomatic and public pressures, he was forced to resign as head of the Federal Narcotics Service and was replaced by someone more complaisant in the eyes of the U.S. State Department and the FBN.
Not surprisingly, Salazar’s work was dismissed by Pablo Osvaldo Wolff in his booklet Marihuana in Latin America. Wolff, who claimed that cannabis did cause psychosis, was much more astute in assuring his opinions were dominant across the relevant UN institutions. Nevertheless, after the 1961 Single Convention was adopted, the UN Bulletin on Narcotics published a review in 1963 that shed substantial doubt on the relationship and, if there was one, about its prevalence.In the review, the Canadian psychiatrist H.B.M. Murphy concluded:
“It is exceedingly difficult to distinguish a psychosis due to cannabis from other acute or chronic psychoses, and several suggest that cannabis is the relatively unimportant precipitating agent only.” He elucidated that “it probably produces a specific psychosis, but this must be quite rare, since the prevalence of psychosis in cannabis users is only doubtfully higher than the prevalence in general populations”.
The debate continues and opinions on how and why cannabis use is related to psychosis and schizophrenia still spark debate among medical observers today. A 2010 editorial in the International Drug Policy Journal called for a more rational approach, decrying that “overemphasis on this question by policymakers has distracted from more pressing issues” and concluded that they should give greater voice to the risks and harms associated with particular cannabis policies and to the evaluation of alternative regulatory frameworks.
Given the decades of research and experience with cannabis prohibition, it seems reasonable to reorient the cannabis policy debate based on known policy-attributable harms rather than to continue to speculate on questions of causality that will not be definitively answered any time soon.
1. See for a good and recent overview: Measham, Nutt and Hulbert (2013).
12 The 1920-21 annual report of the Abbasiya Asylum in Cairo, the larger of Egypt’s two mental hospitals only attributed 2.7 per cent of its admissions to cannabis and even that modest number represented “not, strictly speaking, causes, but conditions associated with the mental disease.” See Kendell (2003).
13 See for instance Murphy (1963)
14 Salazar Viniegra (1938), Campos (2012), pp. 225-26.
According to Salazar “the suggestive load and the ideas which surround marihuana are formidable and have accumulated during the course of time. Marihuana addicts, journalists and even doctors have been the ones charged with transmitting the legend from generation to generation.” See: Bonnie and Whitebread (1974), pp.193-94.
15 Walker (1996), pp. 67-71; Bonnie and Whitebread (1974), pp.193-94; Astorga (2003), p. 219, De Mauleón (2010).
16 Walker (1996), pp. 67-71
17 Pérez Montfort (1995)
18 Carey (2009)
19 Salazar Viniegra (1939)
20 Walker (1996), pp. 67-71
21 Astorga (2003), p. 209; Walker (1996), pp. 67-71
22 Carey (2009)
23 Leopoldo Salazar Viniegra “had the audacity to point out certain facts that are now virtual givens in the literature on drug policy—that prohibition merely spawned a black market whose results were much worse than drug use itself and that, in particular, marijuana prohibition led to the harassment and imprisonment of thousands of users who posed very little threat to society […] Though historians have correctly viewed Salazar as a victim of an increasingly imperialist U.S. drug policy, it has not been sufficiently emphasized that he was also a victim of Mexico’s home-grown anti-drug ideology that still dominates public opinion today.” See: Campos (2012).
24 Murphy (1963)