Depression, anxiety, and psychosis – just a few of the adverse effects that may result from what is often considered a relatively innocuous drug: marijuana. The British forensic psychiatrist Andrew Johns, in his article “Psychiatric Effects of Cannabis,” investigates the potential psychological damage the drug can cause (Johns 2001). He is particularly interested in the effects that heavy or prolonged usage can have on vulnerable populations – specifically youths and those with pre-existing psychiatric issues – and what the clinical implications are. Johns approaches the subject with a meta-analysis, relying on the weight of numerous prior studies to prove his points. His paper effectively reveals the potentially harmful and wide-ranging effects of cannabis use, as it is related to mental illness, dependence, and underlying vulnerabilities. However, because of the exceptionally wide scope of the literature surveyed and the brevity of his research summaries, Johns does not succeed in a convincing demonstration of any of the individual effects addressed. The variance in the purpose and scope of the studies summarized, their divergent approaches, and the diverse populations they sample makes it difficult to accept Johns’ summary conclusions without further investigation.
Johns organizes his paper into three major topics: psychological responses to cannabis use, cannabis dependency, and vulnerabilities that may increase the risk factor of one or both of these. Each of the three topics is further divided into a number of subcategories. For example, the section on psychological responses is divided into “cannabis and mood change,” “cannabis and psychosis,” “cannabis and toxic psychosis,” “cannabis and acute functional psychosis,” “cannabis and chronic psychosis,” “cannabis and amotivational syndrome,” and “cannabis as a risk-factor for serious mental illness.” Some of these are even further subdivided. This might be a reasonable scope for an extended literature review or meta-analysis, but Johns’ paper is only five pages. It is impossible to do anything more than the most cursory presentation of the various findings in such a limited amount of space. He is relying entirely on the authority of other experts in the field, asking the reader to take their results at face value, without any added analysis.
In this five-page article, Johns cites thirty-seven separate studies. This may have been presented more affectively as an annotated bibliography, rather than attempting to put it into narrative form. The author appears rushed at many points, and the flow of the argument is not always coherent because of this. He jumps from study to study – all utilizing different methodologies – and between different cultural groups, many of which may be using marijuana in different forms and for different purposes. It is difficult to know what contributing factors may or may not have been controlled for in the various studies. Johns effectively glosses over any such objections, piling on the evidence. The reader would have to turn to the original papers themselves for any critical analysis, but the sheer amount of work cited prohibits this.
To his credit, there are points where Johns attempts to critique findings, or mention contradictory studies; but there are other times where he makes categorical claims without adequate support. For example, he states that “cannabis-withdrawal syndrome has now been unequivocally demonstrated” (119), describes the symptoms, and ends the section with a single parenthetical citation. He says nothing about the content of the cited study – which had been conducted sixteen years earlier – perhaps assuming that readers will not have the time to investigate it themselves and will simply accept his own conclusions. Later, Johns refers to another study, stating that “Thomas (1996) found that 35% of cannabis users said they could not stop when they wanted to …” (120). He reports additional results from this study, but makes no mention of the sample used. 35% of whom? In most cases, Johns will mention pertinent elements of the sample studied – such as how many, from where, comorbidities, and other factors that might impact the validity of the findings – but here he again glosses over important facts.
Another issue is that Johns occasionally inserts what appear to be his own observations into what is intended as a review of existing research. He makes the claim that “it is a matter of clinical observation that the use of cannabis by some individuals seems to be predisposed by traits such as social anxiety, anxiety or dysphoria” (120). As there is not citation, the reader is left to wonder whose observations he is reporting. Is it from his own experience as a clinical psychiatrist? If so, Johns should be more clear about it. If not, it is an unsubstantiated claim that he has slipped in and might be easily taken as fact.
Johns’ paper is very informative in regards to the harmful effects of cannabis use, but far too condensed to adequately present any findings or support any definite conclusions. It may be that his article serves its purpose in the larger context of the issue of The British Journal of Psychiatry in which it appeared, but it does not stand well on its own, even as a survey. It would be worrying if other authors were to use Johns’ paper as evidence on which to base their own work. As an introduction to an edited anthology of articles it might work well, since the reader can easily jump to the study in question. Considered independently, Johns’ paper relies too much on the authority of other researchers and the avoidance of critical analysis to support any conclusions or clinical recommendations of its own.
- Johns, Andrew. “Psychiatric effects of cannabis.” The British Journal of Psychiatry (2001): 116-122. Print.
