Cannabis and schizophrenia

In May 2004, The Lancet published a study by Dr John Macleod of the University of Birmingham which concluded that there was no proof that cannabis use causes schizophrenia.
“Cannabis use appears to have increased substantially amongst young people over the past 30 years, from around 10% reporting use in 1969-70, to around 50% reporting use in 2001,” reads the study. “If the relation between use and schizophrenia were truly causal, and if the relative risk was around five-fold, then the incidence of schizophrenia should have more than doubled since 1970. However, population trends in schizophrenia incidence suggest that incidence has either been stable or slightly decreased over the relevant time period.”

Previous studies found that people who have schizophrenia are more likely to smoke pot, but researchers were always unclear about whether pot use caused schizophrenia or schizophrenics sought to self-medicate with pot. A June 2000 study, for example, by Doctors Hambrecht and Hafner at Germany’s University of Cologne hypothesized some schizophrenics might use cannabis “for self-medication against (or coping with) symptoms of schizophrenia, particularly negative and depressive symptoms.” It speculated further that such patients probably counterbalance low prefrontal dopamine levels with the dopamine regulating effects of cannabis.

Regardless, by the time such studies make it to press, they are commonly heralded as proof that cannabis causes schizophrenia. In May, the Schizophrenia Society of Saskatchewan issued a public announcement warning that “Marijuana is detrimental to someone who has schizophrenia” and that schizophrenics could be “persuasive and manipulative” in convincing Canadian doctors to prescribe legal med-pot for them.

The researchers who produce such studies are typically in the pocket of pharmaceutical companies, so it bodes well to examine who is behind the research that leads to such misleading claims. In Canada, the largest current funder of such research is the Schizophrenia Research Program Partnership, which receives funding from both the Schizophrenia Society of Saskatchewan and Canada’s largest producer of anti-schizophrenic drugs, AstraZeneca.

It is no coincidence that AstraZeneca’s products are uniquely situated to compete with potential cannabis-based anti-schizophrenic medicines. AstraZeneca’s other big sellers include broad-spectrum pain relievers and anti-migraine drugs ? illnesses that are currently known to be treatable by cannabis therapy.

The perversion of science lays bare the vagaries of human motivation. Research requires millions in funding, donated with the expectation of a return on investment. When the donor is a pharmaceutical company, you can bet that doctors and researchers will produce findings favorable to their patrons.