Cannabis use patterns in first episode psychosis and schizophrenia: A scoping review and case series

Cannabis use is associated with psychosis development and symptom relapse in persons with schizophrenia spectrum disorders (SCZ). As U.S. states legalize cannabis and products increase in potency, it is crucial to better understand recent cannabis use patterns in SCZ.

We conducted a scoping review of research on cannabis quantity, frequency, or type in SCZ after January 2016 and present a case series of cannabis use in inpatients with psychosis (2023-2024).

Scoping review: Of 672 references, ten studies (2631 participants) were included; none were designed to characterize cannabis quantity, frequency, or type of use over time. Cannabis measurement methodology varied; most studies did not use standardized measures. Frequency and quantity of use at baseline were reported by most studies and these ranged widely. At least a minority of participants with SCZ in each study used cannabis very frequently; quantity of used ranged widely from 0.6 ± 0.6 to 3.4 ± 2.2 joints/day. One small study detailed cannabis product type used for THC by SCZ participants (93% used flower, 80% edibles, 60% concentrates).

Participants were inpatients (32.0 ± 14.4 years; 83.3% diagnosed with SCZ) who used cannabis 2.7 ± 2.1 days/week. All used cannabis leaf (3.1 ± 2.3 joints/day); half (all heavy users) also used concentrates (33.3%) or edibles (16.7%).

There is insufficient recent research to confidently characterize cannabis use patterns in clinical populations of persons with SCZ in the era of cannabis legalization. As cannabis legalization expands and product potency increases, further research should characterize cannabis use and its consequences in SCZ.