Cannabis medicines improved some mental disorder symptoms but achieved no remissions in systematic review
A systematic review of 14 RCTs found THC- and CBD-based medicines improved some symptoms across multiple mental disorders when added to standard treatment, but did not produce remission, and the evidence base remains too small for reliable recommendations.
Quick Facts
What This Study Found
Across 14 RCTs (1,629 participants) covering dementia, cannabis/opioid dependence, psychosis, social anxiety, PTSD, anorexia nervosa, ADHD, and Tourette's disorder, cannabis-based medicines as adjuncts were associated with symptom improvements but not remission. Severe adverse effects were rare.
Key Numbers
14 RCTs, 1,629 participants. Diagnoses: dementia, cannabis/opioid dependence, psychosis/schizophrenia, social anxiety, PTSD, anorexia nervosa, ADHD, Tourette's. Improvements in several symptoms. No remission achieved. Severe adverse effects in single cases only.
How They Did This
Review of systematic reviews and RCTs searching five databases (2006-August 2018). Four systematic reviews (of 11 RCTs) and 14 RCTs with 1,629 participants were included. Narrative synthesis due to heterogeneous outcomes. Risk of bias and SIGN checklists applied.
Why This Research Matters
This provides a reality check on cannabis for mental health. Improvements were seen, but no condition achieved remission, and sample sizes remain small. The gap between popular enthusiasm for cannabis as a mental health treatment and the evidence base is clear.
The Bigger Picture
Cannabis-based medicines may be useful adjuncts rather than standalone treatments for mental disorders. The field needs much larger, more rigorous trials with standardized outcomes before treatment recommendations can be made with confidence.
What This Study Doesn't Tell Us
Too heterogeneous for meta-analysis. Small trial sizes across all conditions. Many different THC/CBD formulations and doses used. Adjunctive use only (added to existing treatment), not standalone. Short follow-up periods in most trials.
Questions This Raises
- ?Which specific mental disorders are most likely to benefit from cannabinoid adjunctive therapy?
- ?Would larger trials confirm the improvements seen in these small studies?
- ?What dosing and formulation would be optimal for each condition?
Trust & Context
- Key Stat:
- 14 RCTs, 1,629 patients: symptom improvements but zero remissions across mental disorders
- Evidence Grade:
- Moderate: systematic methodology covering RCTs only, but limited by small trial sizes and heterogeneous outcomes.
- Study Age:
- Published in 2019, covering studies through August 2018.
- Original Title:
- How effective and safe is medical cannabis as a treatment of mental disorders? A systematic review.
- Published In:
- European archives of psychiatry and clinical neuroscience, 269(1), 87-105 (2019)
- Authors:
- Hoch, Eva(9), Niemann, Dominik, von Keller, Rupert(2), Schneider, Miriam, Friemel, Chris M, Preuss, Ulrich W, Hasan, Alkomiet, Pogarell, Oliver
- Database ID:
- RTHC-02073
Evidence Hierarchy
Analyzes all available research on a topic using a structured method.
What do these levels mean? →Frequently Asked Questions
Can cannabis treat mental health conditions?
This systematic review found cannabis-based medicines improved some symptoms across multiple conditions including anxiety, PTSD, and psychosis when added to standard treatment. However, no condition achieved remission, and the evidence base is too small for firm recommendations.
Is cannabis safe for mental health use?
Across 14 trials with 1,629 participants, severe adverse effects were mentioned in single cases only. Side effects occurred but were generally manageable. However, long-term safety data for psychiatric use remain limited.
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Cite This Study
https://rethinkthc.com/research/RTHC-02073APA
Hoch, Eva; Niemann, Dominik; von Keller, Rupert; Schneider, Miriam; Friemel, Chris M; Preuss, Ulrich W; Hasan, Alkomiet; Pogarell, Oliver. (2019). How effective and safe is medical cannabis as a treatment of mental disorders? A systematic review.. European archives of psychiatry and clinical neuroscience, 269(1), 87-105. https://doi.org/10.1007/s00406-019-00984-4
MLA
Hoch, Eva, et al. "How effective and safe is medical cannabis as a treatment of mental disorders? A systematic review.." European archives of psychiatry and clinical neuroscience, 2019. https://doi.org/10.1007/s00406-019-00984-4
RethinkTHC
RethinkTHC Research Database. "How effective and safe is medical cannabis as a treatment of..." RTHC-02073. Retrieved from https://rethinkthc.com/research/hoch-2019-how-effective-and-safe
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.