Many marijuana prohibitionists insist one reason to keep marijuana illegal is that it causes mental illnesses, despite many scientific studies that say otherwise. A new study conducted through the Harvard Medical School adds to that body of research and shows that marijuana use is unlikely to be a cause of schizophrenia. The researchers studied four groups: people with no history of psychosis and no history of marijuana use, people with no history of psychosis who were heavy marijuana users as adolescents,…

There has long been reason to think that marijuana may be helpful to some patients with bipolar disorder, as certain cannabinoids have been shown in lab and animal studies to have effects that ought to be beneficial. Now, a new study from the University of Oslo finds that marijuana use is associated with better neurocognitive functioning in bipolar patients. In various tests of memory, learning, etc., bipolar patients who used marijuana did better than those who didn’t use it – the exact opposite…

At least some in the international news media have belatedly discovered a study casting doubt on the purported link between marijuana use and schizophrenia. I say “belatedly” because the study was published online back in June, although the print version came out this month. A group of British researchers examined a rather basic notion: If marijuana use  causes schizophrenia, then a major increase in marijuana use should lead to an increase in schizophrenia diagnoses in the following years. In an…