Sunday, November 23, 2008
Marijuana Panic Revisited
U.K. journal casts doubt on psychosis connection.
In May of this year, The University College of London reports that different strains of marijuana cause different types of psychological maladies. Shortly thereafter, Prime Minister Brown "publically described new strains of cannabis as 'lethal,' as if they could trigger a fatal overdose," according to an editorial in the Guardian. (See "U.K. Marijuana Panic Continues"). And in August, a mental health story run by the London Daily Mail claimed that smoking a single joint of marijuana increased the risk of developing schizophrenia by 41 per cent—an erroneous statistic that was also hotly contested by various U.K. drug experts. (See "Media Suffers Attack of Cannabis Psychosis").
Now comes a review article from the British Journal of Psychiatry, published by the Royal College of Psychiatrists, strongly suggesting that the odds of an association between cannabis and psychosis is “low.”
A group of drug experts and psychiatrists, including scientists from the University of Bristol, Imperial College London, Cambridge University, and Cardiff University undertook to “systematically review the evidence pertaining to whether cannabis affects outcome of psychotic disorders.”
The group searched relevant databases and compiled a list of more than 15,000 relevant references. A total of 13 longitudinal studies were included in the quality assessment.
The authors concluded that, despite prevailing clinical opinion, it remained “unclear” whether cannabis led to worse outcomes for people with psychosis, “or whether this impression is confounded by other factors. Specifically, the review authors noted that “few studies adjusted for baseline illness severity, and most made no adjustment for alcohol, or other potentially important confounders. Adjusting for even a few confounders often resulted in substantial attenuation of results.”
In the end, “confidence that most associations were specifically due to cannabis is low.”
Graphics Credit: COSMOS