Table of Contents
Clinical Takeaway
Randomized controlled trial evidence for cannabinoids as a primary treatment for mental health conditions and substance use disorders remains limited and inconclusive. Clinicians should not assume efficacy or safety based on approval status alone, as regulatory acceptance does not substitute for robust clinical evidence. Patients considering cannabinoid-based treatment for these conditions should be counseled that current research has not yet established a clear benefit-to-risk profile.
#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
This systematic review of 54 randomized trials found that evidence for cannabinoids treating mental disorders and substance use disorders remains weak and of low certainty. Nearly half the included trials had high risk of bias, and the authors stopped short of drawing firm conclusions about efficacy or safety.
Why This Matters Clinically
Patients and clinicians increasingly turn to cannabis for anxiety, depression, PTSD, and addiction—yet this rigorous evidence synthesis suggests we lack solid proof that it works for these conditions. Understanding the weakness of current evidence should inform the conversation about what we actually know versus what we hope.
Study Snapshot
| Study Design | Systematic review and random-effects meta-analysis of randomized controlled trials |
| Population | 54 trials, 2477 participants (69% male, 31% female, median age 33 years) with mental disorders or substance use disorders |
| Intervention | Cannabinoids as primary treatment for mental or substance use disorders; specific doses and durations not detailed in abstract |
| Primary Outcome | Remission of disorder or reduction in disorder symptoms; safety assessed via adverse events and number needed to treat to harm |
| Key Result | Abstract truncated; states that certainty of evidence for most outcomes was low and 44% of trials had high risk of bias |
Where This Paper Deserves Skepticism
The abstract cuts off before stating the actual efficacy or safety findings, which is problematic for interpretation. We know 44% of included trials had high bias risk and evidence quality was low, but we cannot assess the direction or magnitude of the pooled effects. The heavy male predominance (69%) limits generalizability to women. The median study population age of 33 may not reflect younger or older patients seeking cannabis for psychiatric symptoms.
Dr. Caplan’s Take
When I see a meta-analysis of 54 trials conclude that evidence certainty is low and half the studies carry serious bias, I take that as an honest signal that the field has not yet generated reliable answers. This doesn’t mean cannabinoids have no role in mental health or addiction, but it means we should be circumspect about claims of efficacy and transparent with patients that we are largely in uncertain territory. The gap between clinical enthusiasm and trial evidence here is substantial, and that gap is exactly where good medicine lives: in humility and ongoing observation.
Clinical Bottom Line
The published evidence does not yet support routine use of cannabinoids for mental or substance use disorders; clinicians should set realistic expectations with patients and continue to rely on established first-line treatments while we await higher-quality trials.
|
