A systematic review found insufficient evidence to recommend either THC or CBD for treating schizophrenia

Intravenous THC increased psychosis in stable patients. Two reports on smoked/oral THC in patients with co-occurring CUD found no symptom changes but improved resting-state brain function. CBD 800 mg was as effective as amisulpride for acute psychosis. CBD augmentation results were mixed: 600 mg was not better than placebo, but 1,000 mg reduced symptoms in a sample that included cannabis users.

Systematic review of 11 eligible reports identified from 8 online databases. Studies included placebo-controlled trials and neuroimaging studies using defined doses of THC or CBD in patients with schizophrenia or schizophrenia spectrum disorders.

Despite growing public interest in cannabis-based treatments for mental illness, this review highlights that evidence remains insufficient and highly variable, with THC potentially worsening psychosis and CBD showing mixed results.

The contrast between public enthusiasm for cannabis in mental health and the thin clinical evidence base underscores the need for well-designed, adequately powered trials before medical cannabis can be recommended for psychotic disorders.

Only 11 reports met inclusion criteria. Studies varied widely in dosing, duration, patient populations, and whether cannabis users were included or excluded. Most studies had small samples. Systematic review but not a quantitative meta-analysis due to heterogeneity.