High-strength cannabis and psychosis link confirmed
People using high potency cannabis are five times more likely to suffer psychosis than nonusers, according to a study published in Lancet Psychiatry (doi.org/10.1016/S2215-0366(19)30048-3).
The researchers, from King’s College, London, looked at cannabis use by people in 11 European towns and cities, including London, as well as one region of Brazil. They compared a sample of 901 people who had experienced psychosis with 1237 controls.
Daily cannabis use was associated with increased odds of psychotic disorder compared with never users (adjusted odds ratio [OR] 3·2, 95% CI 2·2–4·1), increasing to nearly five-times increased odds for daily use of high-potency, skunk-like types of cannabis (4·8, 2·5–6·3).
The authors estimate that one in five new cases (20.4%) of psychosis across the study areas may be linked to daily cannabis use, and one in ten (12.2%) linked to use of high-potency cannabis. In London, a fifth (21%) of new cases of psychosis might be linked to daily cannabis use, and nearly a third (30%) to high-potency cannabis, they say.
There was no evidence of an association between less than-weekly cannabis use and psychosis, regardless of potency.