High-potency cannabis and the risk of psychosis

TLDR

Cannabis use is linked to an elevated risk of psychosis, a relationship attributed to the active ingredient Δ9‑THC, and rising Δ9‑THC concentrations in cannabis products have heightened public concern. The study aimed to determine whether individuals experiencing a first episode of psychosis were more likely to use high‑potency cannabis. Researchers collected cannabis‑use data from 280 first‑episode psychosis patients and 174 healthy controls in South London. Cases were not more likely to have ever used cannabis or to have started earlier, but they were significantly more likely to be current daily users (OR 6.4), to have used cannabis for over five years (OR 2.1), and among users, 78 % of cases used high‑potency cannabis versus 37 % of controls (OR 6.8), supporting the hypothesis that Δ9‑THC increases psychosis risk and highlighting public‑health concerns.

Abstract

Background People who use cannabis have an increased risk of psychosis an effect attributed to the active ingredient δ9-tetrahydrocannabinol (Δ9-THC). There has recently been concern over an increase in the concentration of Δ9-THC in the cannabis available in many countries. Aims To investigate whether people with a first episode of psychosis were particularly likely to use high-potency cannabis. Method We collected information on cannabis use from 280 cases presenting with a first episode of psychosis to the South London & Maudsley National Health Service (NHS) Foundation Trust, and from 174 healthy controls recruited from the local population. Results There was no significant difference between cases and controls in whether they had ever taken cannabis, or age at first use. However, those in the cases group were more likely to be current daily users (OR = 6.4) and to have smoked cannabis for more than 5 years (OR = 2.1). Among those who used cannabis, 78% of the cases group used high-potency cannabis (sinsemilla, ‘skunk’) compared with 37% of the control group (OR 6.8). Conclusions The finding that people with a first episode of psychosis had smoked higher-potency cannabis, for longer and with greater frequency, than a healthy control group is consistent with the hypothesis that Δ9-THC is the active ingredient increasing risk of psychosis. This has important public health implications, given the increased availability and use of high-potency cannabis.