A surprising number of scholarly studies in the last 25 years have demonstrated that marijuana use seems to cause an increase in psychoses such as schizophrenia, and somewhat less dramatic mental illnesses such as bipolar disorder.
Let me emphasize: This isn’t just correlation analysis — finding that people with a current mental illness are disproportionately potheads. I am well aware that people with significant mental illness problems tend to “self-medicate” using various psychoactive drugs (including alcohol). No, these are longitudinal studies that show the marijuana use comes first, with the mental illness later in life.
The first of these, involving Swedish conscripts, was published in the Lancet in 1987. Those who had used marijuana heavily by age 18 were six times more likely to develop schizophrenia. A British medical journal paper published in 2002 performed a longitudinal study in New Zealand and found that:
Firstly, cannabis use is associated with an increased risk of experiencing schizophrenia symptoms, even after psychotic symptoms preceding the onset of cannabis use are controlled for. … Secondly, early cannabis use (by age 15) confers greater risk for schizophrenia outcomes than later cannabis use (by age 1. The youngest cannabis users may be most at risk because their cannabis use becomes longstanding.
This paper, from the British Journal of Psychiatry in 2004, should also make you a bit concerned. From the abstract:
On an individual level, cannabis use confers an overall twofold increase in the relative risk for later schizophrenia. At the population level, elimination of cannabis use would reduce the incidence of schizophrenia by approximately 8%, assuming a causal relationship. Cannabis use appears to be neither a sufficient nor a necessary cause for psychosis. It is a component cause, part of a complex constellation of factors leading to psychosis.
There’s unquestionably a genetic component. This Schizophrenia Bulletin (2008) paper tells us:
Cannabis use is considered a contributory cause of schizophrenia and psychotic illness. However, only a small proportion of cannabis users develop psychosis. This can partly be explained by the amount and duration of the consumption of cannabis and by its strength, but also by the age at which individuals are first exposed to cannabis. Genetic factors, in particular, are likely to play a role in the short- and the long-term effects cannabis may have on psychosis outcome. … Evidence suggests that mechanisms of gene-environment interaction are likely to underlie the association between cannabis and psychosis. _________________ "It does not require a majority to prevail, but rather an irate, tireless minority keen to set brush fires in people's minds."
Samuel Adams
The only reason conservatives love bringing up debunked information about marijuana use is because anyone who then argues using valid scientific studies can be labeled as a "drug use proponent." It's a farce!
With almost every state in the union enacting legalization/medical marijuana bills, it's probably time for people to get real about an issue that affects over 70-80% of the population.
Quote:
A recent systematic review concluded that cannabis use increases risk of psychotic outcomes independently of confounding and transient intoxication effects. Furthermore, a model of the association between cannabis use and schizophrenia indicated that the incidence and prevalence of schizophrenia would increase from 1990 onwards. The model is based on three factors: a) increased relative risk of psychotic outcomes for frequent cannabis users compared to those who have never used cannabis between 1.8 and 3.1, b) a substantial rise in UK cannabis use from the mid-1970s and c) elevated risk of 20 years from first use of cannabis. This paper investigates whether this has occurred in the UK by examining trends in the annual prevalence and incidence of schizophrenia and psychoses, as measured by diagnosed cases from 1996 to 2005. Retrospective analysis of the General Practice Research Database (GPRD) was conducted for 183 practices in England, Wales, Scotland and Northern Ireland. The study cohort comprised almost 600,000 patients each year, representing approximately 2.3% of the UK population aged 16 to 44. Between 1996 and 2005 the incidence and prevalence of schizophrenia and psychoses were either stable or declining. Explanations other than a genuine stability or decline were considered, but appeared less plausible. In conclusion, this study did not find any evidence of increasing schizophrenia or psychoses in the general population from 1996 to 2005.
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. The youngest cannabis users may be most at risk because their cannabis use becomes longstanding.
