The link between cannabis and schizophrenia is one that is constantly being leveled.
I have read the many studies that allegedly confirm this link but do mention that other factors must play a part such as the genetic makeup, family history and economic status amongst others.
I have also read studies that defend the use of cannabis amongst schizophrenics as their being self-medicating and I have read plenty of studies recently where cannabis is being used to treat the symptoms of schizophrenia (which woiuld support this).
I have read studies that show that the rate of schizophrenia has remained level since the 1950s while the rate of cannabis use has increased dramatically since this time which would seem to suggest the link may favour the self-medicating theory.
Tonight I decided to do a bit of my own mediocre research following an idea I had.
The idea was to find a world map that visually recorded (using colours) the statistical use of cannabis world wide and a world map that did the same thing for schizophrenia.
THE RESULTS MIGHT SURPRISE YOU!
World map ( so you can see the names of the countries):
As you can see, apart from the anomaly of Papua New Guinea, the recorded incidence of schizophrenia is HIGHEST in the countries that have the LOWEST recorded use of cannabis.
So what’s with Papua New Guinea?
Contrary to all other comparative associations between cannabis use and schizophrenia across the world , (see my post below) , it has the highest rate of cannabis use and one of the highest rates of schizophrenia.
Why is it the exception? What do we know about this country?
Some interesting facts:
1. Papua New Guinea is often labelled as potentially the worst place in the world for gender violence. A 2013 study in The Lancet found that 41% of men on Bougainville Island, Papua New Guinea, reported having raped a non-partner while 14.1% reported having committed gang rape. According to UNICEF, nearly half of reported rape victims are under 15 years of age and 13% are under 7 years of age.
2. Papua New Guinea is one of the most culturally diverse countries in the world. 848 different languages are listed for the country, of which 12 have no known living speakers.
3. Most of the population of over 7 million people live in customary communities, which are as diverse as the languages. It is also one of the most rural, as only 18 per cent of its people live in urban centres. This is interesting since a supposedly top pubmed study in to schizophrenia states that rural communities have the LOWEST rate of schizophrenia and that it is most often found in urban centres.
4. Many people live in extreme poverty, with about one-third of the population living on less than US$1.25 per day.
5. Diet: People typically live in villages that rely on subsistence farming. In some areas people hunt and collect wild plants (such as yam roots) to supplement their diets.
6. Education: A large proportion of the population is illiterate, particularly women.
7. Health: Public expenditure was at 7.3% of all government expenditure in 2006, whereas private expenditure was at 0.6% of the GDP. There were five physicians per 100,000 people in the early 2000s. Malaria is the leading cause of illness and death in New Guinea. Papua New Guinea has the highest incidence of HIV and AIDS in the Pacific region and is the fourth country in the Asia Pacific region to fit the criteria for a generalised HIV/AIDS epidemic
8. The currency of PNG changed from sea shells to money in 1933 but took until the 1950s before it really took in to effect when the mining began seriously in the country and Australians began to migrate to PNG.
This is pubmed study in to cannabis and PNG brought the following interesting finding:
That the apparent exception to the rule for the rest of the world could actually be based on FALSE INFORMATION.
” Prevalence of cannabis use and cultivation
The International Narcotics Control Board (INCB) has stated that “… the prevalence of cannabis abuse in Australia and Papua New Guinea is among the highest in the world”. While this is true for Australia it is a remarkable and unjustifiable comment to make with regard to Papua New Guinea. The reason is that no national data exist on the prevalence of cannabis use in PNG. Furthermore, no data exist from which one can extrapolate to make a reasonably accurate estimate of prevalence. One cannot legitimately compare data derived from a national household probability sample survey in Australia with information derived from quite different sources (not surveys) in PNG.
No studies of the prevalence of cannabis use have been reported covering the rural areas of the nation.”
Conclusion: That the apparent exception of PNG between cannabis use and schizophrenia may be wrong. It was brought in to PNG post war only and mainly after the 1960s/70s with the advent of Australian mining in to PNG. At the same time, the currency of PNG changed from sea shells to money. Although grown a lot, the natives say it is to sell to the white man to pay for education and requirements (according to the study); there is no data to support the claim that it has the highest cannabis use in the world. This would fit with the rest of the indications from the maps below – I.e., highest rates of schizophrenia in countries with the lowest rates cannabis use.
My personal conclusion:
Cannabis has no causal effect on schizophrenia of itself and its use is to self medicate. This is in accordance with the most recent studies that trials are now underway to use cannabis to TREAT psychosis/schizophrenia.