Systematic Review Finds High-Potency Cannabis Linked to Problem Use, But Evidence Is Very Low Quality | Research

The takeaway

A systematic review of 42 studies found suggestive evidence that high-potency cannabis is associated with problematic cannabis use, but findings were less consistent for mental health and other outcomes, with overall evidence rated "very low" certainty.

Policymakers considering potency regulations, cannabis researchers designing studies, and clinicians counseling high-potency cannabis users.

Overall evidence certainty rated "very low" by GRADE

What the researchers found

Of 42 eligible studies, most addressed mental health, problematic cannabis use, and other substance use. Findings in the problematic cannabis use domain were suggestive of an association with higher-potency cannabis. Findings in other domains were less consistent but tended toward poorer outcomes with higher potency. Therapeutic outcomes were limited and mixed. Overall GRADE certainty: "very low."

Why it matters

THC concentrations in cannabis have risen continuously, yet the health impact of high-potency products is poorly understood. This review from the American Journal of Psychiatry provides the most comprehensive assessment to date and finds the evidence base is alarmingly thin.

The numbers in context

4,545 records screened; 42 eligible studies; potency categories from 1% to 60%+ THC; evidence certainty rated "very low" across domains.

How the study worked

Systematic review of five databases. Developed ecologically relevant potency categories: 1-9%, 10-19%, 20-30%, kief/resin (~30-50%), concentrates (60%+). Two independent reviewers for screening, extraction, and quality. GRADE framework for evidence certainty.

What this study cannot tell us

Most included studies were cross-sectional. Few studies examined health outcomes beyond mental health and problem use. Potency measurement methods varied. "Very low" certainty limits confidence in all findings.

How to read the evidence

Rigorous systematic review methodology with GRADE assessment, but the underlying evidence is predominantly cross-sectional and limited in scope.

When this study was published

2025 systematic review published in the American Journal of Psychiatry.

The bigger picture

Policy discussions about potency caps and product regulation are happening with very limited evidence. This review highlights the urgent need for prospective studies, especially on cardiovascular, cancer, and prenatal outcomes, before evidence-based potency policies can be established.

Questions still open

Should potency policies be implemented now despite limited evidence, as a precautionary measure?
Why has research on high-potency cannabis health effects lagged so far behind market trends?

Common questions

Is high-potency cannabis more dangerous?

This review found suggestive evidence linking high-potency cannabis to problematic use patterns, but the overall evidence was rated "very low" certainty, meaning we do not have confident answers yet.

Should there be THC potency limits?

The authors suggest potency policies may be warranted as a precaution while the evidence base improves, but current evidence is insufficient for definitive recommendations.

Read the original research

High-Potency Cannabis Use and Health: A Systematic Review of Observational and Experimental Studies.

The American journal of psychiatry, 182(7), 616-638

View on PubMed ↗Publisher’s paper ↗

Citation

Lake, Stephanie; Murray, Conor H; Henry, Brittany; Strong, Liza; White, Kendall; Kilmer, Beau; Cooper, Ziva D. (2025). High-Potency Cannabis Use and Health: A Systematic Review of Observational and Experimental Studies.. The American journal of psychiatry, 182(7), 616-638. https://doi.org/10.1176/appi.ajp.20240269