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Cannabis use after psychosis onset predicts relapse, adverse outcomes

Continued cannabis use after psychosis onset increased risk for psychosis relapse and led to longer hospital admissions and other adverse outcomes, according to a meta-analysis.

“Some studies implicate cannabis use as a potential risk factor for relapse of psychosis as indexed by readmission to hospital, with some evidence supporting a dose–response association. Other studies report worsening of positive psychotic symptoms or less time to symptom re-emergence in cannabis-using patients with psychosis compared with non-users,” the researchers wrote. “However, although some evidence suggests that discontinuation of cannabis use might lead to a reduction in readmission rates and improvement in symptomatic and functional outcomes of psychosis, other research suggests that this scenario might not necessarily be the case.”

To assess the relationship between continued and discontinued cannabis use after psychosis onset with psychosis relapse, researchers conducted a systematic review and meta-analysis of 24 studies across 16,565 participants.

Continued cannabis users were more likely to experience psychosis relapse than nonusers (P < .0001) and discontinued users (P = .0005), regardless of illness stage.

Continued cannabis users also had longer hospital admissions than nonusers (P = .02).

Cannabis discontinuation was not associated with relapse (P = .82).

Meta-regression analysis indicated continued cannabis use had greater effects on relapse (P = .04), positive symptoms (P = .05) and functioning level (P = .008), but not on negative symptoms (P =. 41), compared with discontinued use.

“Despite the absence of more fine-grained measures, this meta-analysis detected a fairly robust pooled effect of continued cannabis exposure on relapse outcome and other measures suggestive of adverse outcome, which were absent in those who discontinued use of the drug,” the researchers wrote. “The fact that the effects of continued use of cannabis or its discontinuation are consistent across different measures of outcome underlines the importance of addressing continued cannabis use in patients with psychosis in the clinical setting, by emphasizing that outcomes are likely to be better in those who discontinue the drug.”

Disclosure: Schoeler reports no relevant financial disclosures. Please see the full study for a list of all authors’ relevant financial disclosures.