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Panning Pot© John McManamy
We know people with mental illness use marijuana to self-medicate. But for years researchers have been exploring whether in some cases it could be the other way around, causation-wise. Three new studies published in the British Medical Journal give us pause to consider: A study of 50,087 Swedish conscripts (more than 98 percent of the male population aged 18 to 20) found those who reported smoking marijuana more than 50 times during adolescence were three times more likely to develop schizophrenia after 27 years than those who did not use the drug. The study ruled out other drugs and pre-existing conditions. Altogether, 5,391 subjects (10.8 percent of the cohort) had used cannabis and 73 (1.4 percent) developed schizophrenia, representing an increased risk of 30 percent, with the association strongest in those hospitalized within five years of conscription. No association was found between cannabis and other psychotic illness. According to the study's authors: "Molecular studies have shown that tetrahydrocannabinol, the active component of cannabis, increases release of dopamine in the mesolimbic pathway. Given the suggested relation between increased mesolimbic dopamine and positive symptoms of schizophrenia, such observations provide support for the hypothesis that cannabis may act as a risk factor for this disorder." The authors of the study suggest that the results are understated, as fewer subjects in this cohort claimed to have used drugs compared to anonymous surveys. A New Zealand study of 1037 individuals born in 1972-73 corroborated the Swedish study and found that early use (at age 15) conferred greater risk for schizophrenia outcomes than at age 18, leading the study's authors to conclude: "Our findings suggest that cannabis use among psychologically vulnerable adolescents should be strongly discouraged by parents, teachers, and health practitioners. Policy makers and law makers should concentrate on delaying onset of cannabis use." Meanwhile, an Australian study of 1,601 students aged 14 to 15 followed found 60 percent had used cannabis by age 20 and seven percent were daily users at that point. After adjusting for other substances, researchers found daily use among young women was associated with a fivefold increase in the odds of depression and anxiety. Weekly or more frequent use corresponded with a twofold increased risk. An editorial in the same issue of the BMJ cited other studies in support of these three, noting "the explanation most accepted is that cannabis triggers the onset or relapse of schizophrenia in predisposed people and also exacerbates the symptoms generally." The authors of the Swedish study conjecture that based on their findings, 13 percent of cases of schizophrenia could be prevented if cannabis use were eliminated. "Such risks," they go on to say, "need to be considered in the current move to liberalize and possibly legalize the use of cannabis in the United Kingdom and other countries. Go To Page: 1 2
The copyright of the article Panning Pot in Depression is owned by Kathy Brewis. Permission to republish Panning Pot in print or online must be granted by the author in writing.
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