Systematic review of 58 CBD trials found it works for anxiety but has inconsistent results for other conditions | Research

The takeaway

A systematic review of 58 randomized trials found CBD appears to be anxiolytic, but its effectiveness for other non-seizure conditions including psychosis, schizophrenia, and substance use disorders was highly variable.

Consumers considering CBD products, clinicians asked about CBD, and researchers designing CBD trials.

Anxiety was the only condition with consistent positive CBD results

What the researchers found

CBD appears to be anxiolytic (anxiety-reducing). Its effectiveness for other conditions was highly variable. Mental health was the most studied topic (53% of trials). 72% of studies had fewer than 40 participants. Doses ranged from 400 micrograms to 6,000 mg. CBD was generally safe and well-tolerated even at high doses.

Why it matters

As CBD products flood the market with claims for dozens of conditions, this comprehensive review clarifies that only for anxiety does the evidence consistently support effectiveness, while most other claims lack reliable evidence.

The numbers in context

58 RCTs from 8 countries. 47% conducted in healthy populations. 14% restricted to males. 72% had fewer than 40 participants. Doses ranged 400 mcg to 6,000 mg. 53% studied mental health outcomes. Anxiety showed most consistent positive results.

How the study worked

Systematic review of 58 randomized clinical trials from seven databases across eight countries. Excluded seizure-related studies. Included only trials using CBD derived from Cannabis sativa with <3% THC. Independent dual reviewing and risk of bias assessment.

What this study cannot tell us

Most included trials were small (72% had fewer than 40 participants). The wide range of doses and formulations makes cross-study comparison difficult. Some conditions had very few trials.

How to read the evidence

Strong: comprehensive systematic review of 58 RCTs with rigorous methodology and dual reviewing.

When this study was published

Published in 2022.

The bigger picture

The huge gap between market claims for CBD and the actual clinical trial evidence is starkly illustrated by this review. Larger, more rigorous trials are urgently needed for most proposed indications.

Questions still open

Why does CBD work more consistently for anxiety than other conditions? What is the optimal dose for anxiolytic effects? Would standardized CBD products perform better in trials than the heterogeneous products tested?

Common questions

Does CBD work for anxiety?

The evidence is most consistent for anxiety. Across multiple trials, CBD appeared to have anxiolytic (anxiety-reducing) properties. For other conditions, results were inconsistent.

Why are results so inconsistent for other conditions?

Most studies had very small samples (under 40 participants), used widely varying doses (400 mcg to 6,000 mg), and tested different CBD products. This variability makes it difficult to draw clear conclusions.

Is CBD safe?

In the studies reviewed, CBD was generally safe and well-tolerated, even at high doses. However, the authors note that clearer dosing guidelines and increased regulation of CBD products are needed.

Read the original research

The Effectiveness and Safety of Cannabidiol in Non-seizure-related Indications: A Systematic Review of Published Randomized Clinical Trials.

Pharmaceutical medicine, 36(6), 353-385

View on PubMed ↗Publisher’s paper ↗

Citation

Tang, Yuni; Tonkovich, Kolbi L; Rudisill, Toni Marie. (2022). The Effectiveness and Safety of Cannabidiol in Non-seizure-related Indications: A Systematic Review of Published Randomized Clinical Trials.. Pharmaceutical medicine, 36(6), 353-385. https://doi.org/10.1007/s40290-022-00446-8