Joel Yager, MD reviewing Setién-Suero E et al. Acta Psychiatr Scand 2019 Aug 5

Patients who used cannabis during their first psychotic episodes and never stopped had worse outcomes 10 years later than ex-users and never-users.

(High Potency) Cannabis contributes to the risk for first-episode psychosis in adolescents and young adults. These investigators used data from an interventional program enrolling patients with first-episode psychosis to examine the impact of cannabis cessation versus continuation at 10-year follow-up in patients from a single Spanish geographical area (baseline age range, 15–60).

Patients meeting criteria for substance dependence other than for nicotine were excluded. Of 307 enrolled patients, 209 were examined 10 years later (54% men). Of the follow-up group, 79 (38%) were self-reported cannabis users at baseline (73% men; mean age at cannabis use onset, 17; mean consumption, 26 joints/week). Compared with baseline nonusers, initial users were more likely to be younger, male, and less educated and to have lower IQs, lower neurocognitive processing speeds, and poorer academic performance and adjustment in adolescence.

In a subanalysis of 191 patients (baseline cannabis users, 68) with additional assessments at 3 years, most users who stopped cannabis had done so by 3 years. The 10-year follow-up analysis compared persistent cannabis users (8%), ex-users (28%), and never-users (64%) and adjusted for sex and age. Although some improvement was seen overall, persistent users consistently showed more severe positive symptoms and poorer functioning than ex-users and never-users, who did not differ from one another. The three groups showed no long-term differences in cognitive function.