News » Study Linking Cannabis and Early-Onset Schizophrenia Flawed

A study published in the American Medical Association’s Archives of General Psychiatry (online) has made some big headlines in the recent press. Headlines like “Researchers Link Marijuana and Earlier Onset of Psychosis” (NPR) and “Marijuana Schizophrenia Link: Drug Could Cause Earlier Onset of Psychosis” (Huffington Post). Those, indeed, are the general conclusions for the study, but the study itself has two major flaws that undermine its findings. You won’t see either of these flaws pointed out in the popular media, of course.

Why?

Because that would require that those reporters actually read the study itself and then apply some logic and reasoning of their own. Something most mainstream reporters are apparently unable to do – or aren’t allowed to do, take your pick.

First, the study itself. It’s titled Cannabis Use and Earlier Onset of Psychosis and was compiled by several Australian researchers and published on February 7, 2011 at the Archives of General Psychology. It’s available online, for free, to anyone who cares to read it.

The research is a compilation (rather than an original study) of results from earlier published scholarly articles – 83 of them to be exact – dealing with the relationship between marijuana (cannabis) and schizophrenia and related psychosis.

This meta-analysis, according to the authors’ conclusions, provides evidence for a relationship between cannabis and earlier onset of psychotic illnesses. To the tune of possibly causing schizophrenia to be diagnosed an average of 2.7 years earlier than otherwise. One thing often missed or buried in these reports is the fact that those included in the studies already had a predisposition towards psychosis (usually by genetics).

All of this has resulted in a slew of reportage from various media outlets regarding this “new evil” for marijuana. The study, however, has two major flaws that undermine its findings. One of these is addressed by the authors themselves as a limitation that could not be overcome. That was the possible link of tobacco with these same findings.

Studies in the past have shown that most marijuana users are also tobacco smokers – either separately or by mixing with cannabis. This could not be removed from the study, which means that it could be tobacco itself causing the problem. Or any of the 599 ingredients found in cigarettes such as ammonia, various ethyls, and any of dozens of acids and carcinogens. It could be those wonderful things that are actually triggering the early onset psychosis.

Similarly, and not addressed by the study’s authors, is the fact that other drugs were also not accounted for in many of the papers used to make this analysis. So it’s not possible to know if these marijuana users, in many cases, were also cocaine, heroine, LSD, etc. users; either directly or indirectly (more on that in a moment). The only substance accounted for in the analysis was alcohol – which was exonerated as a threat.

The study did, however, find that a higher proportion of cannabis users did have earlier onset psychosis, but this is not conclusive because of all of the unaccounted for inputs that could not be rectified.

The trouble with studies of the type used in this meta-analysis is that they are usually based on indirect observation – they are based on what patients tell them and what simple drug tests might say and not on direct experimentation. Obviously, direct experimentation is not possible for this type of inquiry – using human guinea pigs is unethical. So studies of this nature are, by nature, highly subjective. Here’s why:

First, the patients in the study are subjectively giving answers to questions – the questions themselves are usually crafted in such a way that the researchers can be reasonably sure they’re getting a quantifiable answer, but there is always room for question. One patient’s “twice a week” pipe smoking might be another patient’s “twice a week, suck down an eighth bender”, but the study will still show “twice a week.” Further, one patient’s source for cannabis might be routinely cutting it with other substances (catnip, parsley, tobacco, whatever) or adding something to make it “chronic” while another source may not be.

Secondly, the studies themselves are often done years after the fact. For instance, the patients in one cannabis-marijuana study might have been diagnosed with schizophrenia 5 years ago, so the questions being asked are being answered from memory 5 or more years after the fact.

All of this lends question to the study’s outcomes. This same reasoning is why many doctors refuse to accept data showing that cannabis effectively, reliably and safely alleviates pain. Studies showing this to be the case are based on subjective patient feedback and are thus questionable.

The problem here is not with the study itself, though it is flawed, but with the way it’s been reported in the mainstream. It’s more evidence of the bad reportage and objective-driven editorial behind most mainstream media.

Tags: ama, american medical association, cannabis, marijuana, psychosis, schizophrenia, science