In these crazy times, it seems that the anti-cannabis movement has finally come full-circle. I'm sure we have all heard about Reefer Madness, a movie from 1936 that tried to scare people about the supposed evils of cannabis. You know--murder, rape, suicide, promiscuity, and of course insanity. Worse than even heroin, it was alleged at the time. People were led to believe these outlandish claims, which contributed to cannabis becoming illegal by 1937 thanks to Harry Anslinger. Not like that stopped very many people from using it of course--it has gone from negligible levels of use back then to literally millions of users today.
As far back as the La Guardia Committee Report in 1944, such claims were largely debunked, and by 1951 Harry Anslinger changed his propaganda to claim the (now widely discredited) gateway theory, as well as the idea that it made users too peaceful to fight the Reds (quite the opposite of the original legend). In the 1960s it became associated with the anti-establishment counterculture, thus "amotivational syndrome" was the latest allegation leveled against it, along with ideas of general licentiousness, rebellion and lawlessness. Nixon even associated it with communism among other things, and was less than pleased when a study that he commissioned found results that were not to his liking. The 1970s brought several later discredited studies alleging serious brain damage (e.g. Dr. Heath's now infamous monkey study) and even genetic mutations, but claims of Reefer Madness had largely been abandoned by then. In the 1980s and 1990s, many of these themes kept on being recycled, plus the idea that had become much more potent (and dangerous) than it was in the 1960s and 1970s when the Baby Boomers were young.
But now it seems that claims of Reefer Madness, or at least the psychosis part of the legend, has made a comeback in recent years. Just when it seems that legalization is right around the corner, no less. Several recent studies claim to show a link between cannabis and psychosis, including schizophrenia. But is it true?
The best one can honestly say is that, overall, the jury is still out. Correlation is not the same as causation, and there are numerous other variables to consider. Take, for example, a study done last month that found that the cannabis-using individuals who did develop schizophrenia do so 2.7 years earlier than nonusers. This was a meta-analysis of many other studies, and of course the media took it and ran with it. But not all experts agree. Dr. Mitch Earleywine, an expert on cannabis, has his doubts about the study's ability to demonstrate a causal relationship. And one must remember that even if it did, it does not mean that it causes cases that would not otherwise have occurred--the study was not designed to look at that. In any event, the study design cannot completely rule out reverse causation (such as self-medication) either. Indeed, quite a few studies, including one by Earleywine himself, have suggested reverse causation or a common vulnerability as a possible explanation for the rather complex association between cannabis and psychosis.
So what about the most recent study that found that cannabis use is associated with a 1.9-fold increased odds of later psychotic symptoms? Unlike most other studies, this was a ten-year prospective longitudinal study (in Germany) that followed participants before they began using cannabis, and controlled for numerous confounders such as family history, urbanicity, childhood trauma, and use of other drugs. And there was no evidence of psychotic symptoms predicting later cannabis use, in contrast to some other prospective studies. However, several caveats apply here. First, it looked as psychotic symptoms (a fairly broad category that is quite prevalent in the general population) rather than actual psychotic disorders such as schizophrenia. Such symptoms as well as cannabis use were both self-reported, making reporting bias possible (i.e. those who are more frank about admitting to crazy thoughts may be more likely to admit to using an illicit substance). In fact, some such symptoms are remarkably similar to simply being stoned! Secondly, any epidemiological study with an odds ratio (or relative risk) of less than 2.0 needs to be taken with at least a grain of salt, if not a whole pound. Thirdly, while other drugs were controlled for, residual confounding is possible since some poly-drug users to admit to using cannabis (a more socially acceptable drug) but not, say, crystal meth, thereby making cannabis the "fall guy" for other unreported drugs. Lacing without the user's knowledge is also a possibility due to the illegality of the plant. And like most studies on the matter, tobacco use was not directly controlled for in this study (or last month's one), which may be difficult to disentangle since the vast majority of European cannabis users also use tobacco (often mixed in their joints), making tobacco a possible "dark horse". Nicotine (a known neurotoxin) is, after all, the number one drug used by psychotic people for whatever reason. Finally, the study did not distinguish between light and heavy use of cannabis, or other substances for that matter, making it impossible to test for a dose-response relationship. But of course none of these caveats have stopped the MSM from claiming that this study is the final word on the matter.
Another obsevation we have noticed is that the vast majority of studies (including the one above) that appear to support a causal relationship have Dr. Robin Murray (UK) and/or Dr. Jim van Os (Netherlands) in the list of authors. This is especially true of studies where the relationship appears unidirectional. Not to accuse them of anything, of course, but the idea that the relationship is causal happens to be a pet theory they have both shared for nearly a decade. Hmmmm.
If cannabis really did cause cases of schizophrenia and other persistent psychotic disorders that would not otherwise have occurred, then the massive increase in cannabis use (by orders of magnitude) from the early 1960s to the present should have been followed by at least a modest increase in the prevalence and incidence of such disorders in the long run. However, studies in both the UK and Australia have shown that this did not in fact occur, despite the British tabloids repeatedly claiming otherwise. In most Western countries, rates of psychosis have generally been stable or declining in spite of massive increases in cannabis use, and countries with very low use of cannabis (such as Sweden and Japan) do not have a significantly lower prevelance of psychotic disorders than countries with very high use (such as Canada and the USA). Nor is there any hard evidence that the Netherlands has become any crazier since their policy of quasi-legalization began in 1976. Thus, there is a major hole in the theory of causality that is rather difficult to explain away.
So what do we know for certain at this point? It is technically true that cannabis, especially when taken at very high doses, may cause a transient "toxic psychosis" and/or delirium in some people, albeit rarely. It is also true that at least some (but not all) people with schizophrenia and other psychotic disorders (including the early stages) are particularly prone to bad reactions and can see exacerbations of their symptoms when using the drug, and those individuals should thus avoid it. But the same can be said about several other licit and illicit subtances, even caffeine (including, but not limited to, energy drinks). And contrary to what the alcohol supremacists would like to believe, there is also such a thing as alcohol-induced psychosis, which can sometimes be misdiagnosed as schizophrenia. In addition, one should also bear in mind that there is more than one active ingredient in cannabis--while THC in isolation can produce transient anxiety and quasi-psychotic symptoms in some people, another component (cannabidiol) appears to actually have anti-psychotic and anti-anxiety effects, essentially blocking much of the adverse effects of THC. These two cannabinoids (and others) vary widely among the numerous strains of cannabis, with some strains having lots of one and negligible amounts of the others, and other strains being more balanced. But thanks to prohibition, it ends up pretty much being a guessing game.
Even if the putative link between cannabis and schizophrenia were somehow truly causal, which we doubt, it hardly follows that keeping cannabis illegal (and thus unregulated) is the best public policy response. In fact, a study using a mathematical model that assumes a causal relationship (of a magnitude similar to most of the studies that found an association) predicts that literally several thousand people would have to be prevented from using cannabis in order to prevent a single case of schizophrenia! Even somehow making cannabis completely disappear tomorrow would, at best, lead to 10% fewer cases eventually. Not only is such a Herculean task practically impossible, it would be a utilitarian's worst nightmare. The social costs of prohibition is far higher than the social costs of cannabis, and the latter are also lower than the social costs of alcohol and tobacco, even on a per-user basis. It is thus far better to legalize, tax and regulate it than it is to prohibit it (and enrich violent criminals) for the ostensible purpose of protecting a small percentage of the population from themselves.
While we do not encourage anyone to use cannabis or any other psychoactive substance, the TSAP unequivocally supports legalization of cannabis, and taxation and regulation in a manner similar to how alcohol and tobacco are treated in most of the Western world. As we have said before, we are not a pro-drugs party, but rather pro-liberty and anti-tyranny. In a free society, our bodies (and minds) do not belong to the Almighty State, regardless of whether the state provides anything for the people. What we find most fascinating is how cannabis seems to cause anxiety, panic, paranoia, and psychosis in those who DON'T use it--especially among politicians.
We have had enough Reefer Madness for one century already. Its time for some "Reefer Sanity" for the 21st century.