Table of Contents
Clinical Takeaway
Randomized controlled trial evidence on cannabinoids for mental health and substance use disorders remains limited and inconclusive, with current data insufficient to establish clear efficacy or a well-defined safety profile for these indications. Clinicians should interpret existing positive findings cautiously and recognize that approval of cannabinoids for psychiatric conditions has outpaced the supporting clinical evidence.
#1 The efficacy and safety of cannabinoids for the treatment of mental disorders and substance use disorders: a systematic review and meta-analysis.
Citation: Wilson Jack et al.. The efficacy and safety of cannabinoids for the treatment of mental disorders and substance use disorders: a systematic review and meta-analysis.. The lancet. Psychiatry. 2026. PMID: 41856154.
Design: 6 Journal: 4 N: 0 Recency: 3 Pop: 3 Human: 1 Risk: -2
- Preclinical only
Abstract: BACKGROUND: Mental disorders and substance use disorders (SUDs) are among the leading reasons for which the medical use of cannabinoids has been approved, but their efficacy and safety in treating these conditions is yet to be established. We conducted a systematic review and meta-analysis of randomised controlled trials (RCTs) testing the efficacy and safety of cannabinoids as the primary treatment for mental disorders or SUDs. METHODS: We searched Ovid MEDLINE, PsychINFO, Cochrane Central Register of Controlled Clinical Trials, Cochrane Database of Systematic Reviews, and Embase for peer-reviewed articles published between Jan 1, 1980, and May 13, 2025, evaluating the efficacy of cannabinoids in reducing or treating mental disorders and SUDs as the primary indication. Primary outcomes were remission of disorder or reduction in disorder symptoms. Safety was assessed via synthesis of all-cause and serious adverse events, which was used to calculate the number needed to treat to harm (NNTH). Two independent reviewers screened all studies and performed data extraction. Evidence was synthesised as odds ratios (ORs) for dichotomous measures and standardised mean differences (SMDs) for continuous measures, via random-effects meta-analysis in Review Manager, version 5.4. Risk of bias was assessed using the Cochrane Collaboration Risk of Bias 2.0 tool. We evaluated the quality of the primary outcomes using the GRADE framework. The study was registered with PROSPERO (CRD42023392718). FINDINGS: 54 trials were identified for inclusion (2477 participants; 1713 [69%] males, 764 [31%] females; median age 33·3 years [IQR 28·1-38·05; ethnicity data not available). 24 (44%) of these trials had a high risk of bias, and the certainty of evidence for most outcomes was low. Our meta-analysis revealed that a combination of cannabidiol and delta-9-tetrahydrocannabinol reduced cannabis withdrawal symptoms (SMD -0·29, 95% CI -0·57 to -0·02) and weekly grams of cannabis use (-1·00, -1·69 to
What This Study Teaches Us
A systematic review of 54 randomized trials found low-certainty evidence that cannabinoids treat mental disorders and substance use disorders as primary therapies. Nearly half the included studies had high risk of bias, and the abstract does not detail what the meta-analysis actually found regarding efficacy or safety.
Why This Matters Clinically
Patients and clinicians often turn to cannabinoids hoping for relief from depression, anxiety, PTSD, and addiction. This review suggests the evidence base is weaker and more problematic than the approval landscape implies, which should inform both prescribing decisions and patient expectations.
Study Snapshot
| Study Design | Systematic review and meta-analysis of randomized controlled trials published 1980-May 2025 |
| Population | 54 RCTs, 2477 total participants (69% male, 31% female, median age 33.3 years) with mental disorders or substance use disorders |
| Intervention | Cannabinoids as primary treatment for mental or substance use disorders (specific cannabinoid types, doses, and durations not specified in abstract) |
| Primary Outcome | Remission of disorder or reduction in disorder symptoms; safety assessed via all-cause and serious adverse events |
| Key Result | Abstract does not report the actual efficacy or safety findings; notes 44% of trials had high risk of bias and certainty of evidence was low for most outcomes |
Where This Paper Deserves Skepticism
The abstract is incomplete and does not report the actual meta-analysis results, making it impossible to assess specific efficacy claims or harm estimates from this summary alone. The high risk of bias in 44% of included trials and low GRADE certainty undermines confidence substantially. The male predominance (69%) and median age of 33 years limit generalizability to older adults, women, and other populations commonly seeking cannabinoid treatment for psychiatric symptoms.
Dr. Caplan’s Take
I appreciate a well-executed systematic review that holds cannabinoid psychiatry to the same standard we’d apply to any other therapeutic claim. What strikes me is not just the low certainty of evidence, but that the authors felt obliged to review and synthesize trials where bias was endemic. This suggests we’ve been approving and promoting cannabinoids for mental health and addiction in the absence of a solid RCT foundation. Until the full paper is available, I’m cautious about how to counsel patients, but the preliminary signal here is that we need better, larger, longer studies before cannabinoids should be considered first-line or definitive therapy for these conditions.
Clinical Bottom Line
Current evidence supporting cannabinoids for mental disorders and substance use disorders is low-certainty and hampered by methodological problems in the underlying trials. Clinicians should discuss this evidentiary gap candidly with patients considering cannabinoids for these indications.
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