Musa Sami, a researcher and academic psychiatrist at King's College London, has examined cannabis usage trends and schizophrenia trends, and the numbers he’s seen have led him to ask an interesting question: “If cannabis is getting stronger, why aren’t cases of schizophrenia rising?”
In his article, Mr. Sami looks at a long standing theory that cannabis users have a higher risk of developing schizophrenia. Reflecting upon that theory, he came up with an interesting counterpoint, "Since the 1960s, cannabis potency and rates of use have risen in many Western countries with high-potency strains now dominating the market. If cannabis were a cause of psychosis, we would expect that, as this increased, rates of schizophrenia would increase alongside it. But this has not happened."
He contends that this fact suggests that a cause-and-effect relationship between smoking cannabis and schizophrenia may not exist.
He considered a study which showed that schizophrenics have more psychotic-like experiences using cannabis. And then he looked at numbers his team developed which showed that cannabis users who had psychotic-like experiences were the most likely to quit in the future. Based upon the two factors he believes that people at risk of schizophrenia would actually be the least likely to continue using cannabis; raising questions about the purported link between cannabis and psychosis.
Mr. Sami is the first to admit that this is a hypothesis; and a difficult one to test without long term, expensive studies. Regardless of that factor, the article and his thoughts are worthy of consideration.