Today, a landmark study published in the prestigious Lancet Psychiatry Journal finds that daily use of high potency marijuana is linked to greater rates of psychosis in Europe. According to the study, an estimated five in ten new cases of psychosis in Amsterdam and three in ten new cases in London are linked with high potency marijuana use.
“This study is groundbreaking,” said Dr. Kevin Sabet, president of Smart Approaches to Marijuana (SAM) and a former Obama Administration drug policy advisor. “It is the first to show how marijuana impacts population rates of psychosis – and it’s results are chilling. For years we have known that low potency marijuana was damaging to mental health. Now the scientific literature is catching up with the rapidly increasing THC potency we are seeing on the market today.”
Numerous studies have shown a causal link between marijuana use and onset of severe mental health issues, such as psychosis and schizophrenia, but this is the first study to showcase the link at a population level. The study finds that daily, average potency marijuana users were three times more likely to be diagnosed with first episode psychosis compared to non-users. With daily use of high potency marijuana, this number increased to five times more likely.
“Our findings are consistent with previous studies showing that the use of cannabis with a high concentration of THC has more harmful effects on mental health than the use of weaker forms. They also indicate for the first time how cannabis use affects the incidence of psychotic disorder at a population level,” said Dr Marta Di Forti, lead author from the Institute of Psychiatry, Psychology, and Neuroscience at King’s College London, UK. “As the legal status of cannabis changes in many countries and states, and as we consider the medicinal properties of some types of cannabis, it is of vital public health importance that we also consider the potential adverse effects that are associated with daily cannabis use, especially high potency varieties.”
Moreover, the study found that instances of first time psychosis in London would be cut by a third if high potency marijuana products were no longer available.
Sabet continued, “Lawmakers considering marijuana legalization are not learning about studies such as this from the well-heeled marijuana industry lobbyists. We will get this study, and others like it, in front of lawmakers at all levels of government to educate them on the real impact of allowing the commercialization of high potency marijuana to spread.”