Meta-analysis of 31 RCTs found limited evidence for cannabinoids treating psychiatric disorders | Research

The takeaway

A systematic review and meta-analysis of 31 randomized controlled trials found limited evidence that cannabinoid products acutely treat a narrow range of psychiatric symptoms, with no evidence supporting mid- to long-term effectiveness for any psychiatric disorder.

Psychiatrists, patients considering cannabis for mental health conditions, and researchers studying cannabinoid therapeutics.

No evidence for mid- to long-term effectiveness for any psychiatric disorder

What the researchers found

Of 31 RCTs (10 for cannabis use disorder, 6 for schizophrenia, 5 for opioid/tobacco use, 3 for anxiety, 2 each for Tourette's and anorexia, 1 each for ADHD, PTSD, and OCD), the review found limited evidence for acute symptom management in select conditions. No evidence supported mid- to long-term effectiveness. No study endorsed cannabis flower as treatment for any psychiatric disorder. Evidence quality was generally low to moderate.

Why it matters

Despite widespread consumer belief in cannabis for mental health, the highest level of evidence (RCTs) provides only limited support for acute use in narrow applications and no support for ongoing treatment of any psychiatric disorder.

The numbers in context

2,397 papers identified; 31 RCTs included; 10 for CUD, 6 for schizophrenia, 5 for opioid/tobacco, 3 for anxiety; low-to-moderate evidence quality overall

How the study worked

Systematic review and meta-analysis searching 8 databases from inception to September 2020. Of 2,397 papers identified, 31 RCTs met inclusion criteria. Risk of bias was assessed using the revised Cochrane tool.

What this study cannot tell us

Heterogeneity across RCTs in products, doses, and outcomes limits meta-analytic pooling. Many included trials were small. Rapid evolution of cannabis products means newer formulations are understudied. Publication bias possible.

How to read the evidence

Comprehensive meta-analysis of 31 RCTs across 8 databases with Cochrane risk-of-bias assessment, though underlying trial quality was mostly low to moderate.

When this study was published

Published in 2021 covering literature through September 2020.

The bigger picture

This meta-analysis creates an important reality check against the growing popular narrative that cannabis can treat psychiatric conditions. While some acute effects are supported, the gap between consumer expectations and clinical evidence remains wide.

Questions still open

Could larger, better-designed RCTs change these conclusions? Are specific cannabinoid formulations more promising for specific disorders? Why is there such a disconnect between patient-reported benefits and RCT results? Could combining cannabinoids with psychotherapy improve outcomes?

Common questions

Can cannabis treat depression or anxiety?

This meta-analysis of 31 RCTs found only limited evidence for acute symptom management in select conditions and no evidence for ongoing treatment of any psychiatric disorder, including depression and anxiety.

What about CBD specifically?

CBD was tested in several included trials, particularly for schizophrenia and anxiety. While some acute effects were noted, the overall evidence did not support CBD as a standalone treatment for any psychiatric disorder.

Read the original research

Potential therapeutic benefits of cannabinoid products in adult psychiatric disorders: A systematic review and meta-analysis of randomised controlled trials.

Journal of psychiatric research, 140, 267-281

View on PubMed ↗Publisher’s paper ↗

Citation

McKee, Kyle A; Hmidan, Amira; Crocker, Candice E; Lam, Raymond W; Meyer, Jeffrey H; Crockford, David; Trépanier, Annie; Aitchison, Katherine J; Tibbo, Philip G. (2021). Potential therapeutic benefits of cannabinoid products in adult psychiatric disorders: A systematic review and meta-analysis of randomised controlled trials.. Journal of psychiatric research, 140, 267-281. https://doi.org/10.1016/j.jpsychires.2021.05.044