- Paucity of evidence supports medical cannabis treatment of mental health disorders.
- Editorial states included psychiatric disorders have no common cause or pathophysiology.
- Absence of evidence may also reflect research barriers.
Why this matters
- More research is needed before cannabinoids can be broadly recommended for symptomatic, long-term mental disorder (depression, ADHD, Tourette's syndrome, posttraumatic stress disorder [PTSD], psychosis) treatment.
- 83 eligible studies (40 randomized controlled trials [RCTs]; n=3067) included:
- Depression (42 studies; 23 RCTs; n=2551), anxiety (31 studies; 17 RCTs; n=605), Tourette's syndrome (8 studies; 2 RCTs; n=36), ADHD (3 studies; 1 RCT; n=30), PTSD (12 studies; 1 RCT; n=10), psychosis (11 studies; 6 RCTs; n=281).
- Pharmaceutical tetrahydrocannabinol-cannabidiol significantly reduced anxiety symptoms vs placebo: pooled standardized mean difference (SMD), −0.25 (95% CI, −0.49 to −0.01).
- No significant improvements in depression symptoms vs active comparators or placebo (pooled SMD, −0.05 [95% CI, −0.22 to 0.13]).
- No significant benefit for Tourette's syndrome, ADHD.
- Worsening negative psychosis symptoms (SMD, 0.36; 95% CI, 0.10-0.62).
- Pooled analysis (10 studies) showed significantly more adverse events vs placebo (OR, 1.99; 95% CI, 1.20-3.29).
- Systematic, meta-review assessing effectiveness, safety of medicinal cannabinoids for treating mental disorders, related symptoms.
- Funding: Therapeutic Goods Administration, Australia, others.
- Poor-quality data.
- Small study sizes.
- Heterogeneity lacking.
- Selection bias.