First clinical trial finds CBD at 400mg and 800mg reduced cannabis use compared to placebo | Research

The takeaway

In the first randomized clinical trial of CBD for cannabis use disorder, CBD at 400mg and 800mg daily was safe and more effective than placebo at reducing cannabis use, while CBD at 200mg was eliminated as ineffective.

People wanting to reduce cannabis use, addiction medicine specialists, and clinical trial researchers.

CBD 400mg reduced THC metabolites by 94 ng/mL vs placebo

What the researchers found

CBD 400mg reduced urinary THC metabolites by 94 ng/mL and increased abstinent days by 0.48 per week compared to placebo. CBD 800mg reduced metabolites by 72 ng/mL and increased abstinence by 0.27 days per week. CBD 200mg was eliminated as inefficacious at interim analysis.

Why it matters

No pharmacological treatment currently exists for cannabis use disorder. This trial provides the first clinical evidence that CBD could fill this gap, with the 400mg dose showing the strongest overall results.

The numbers in context

82 participants enrolled. CBD 400mg: THC-COOH decreased by 94.21 ng/mL (95% CI -161.83 to -35.56), abstinence increased by 0.48 days/week. 94% completed treatment. No severe adverse events.

How the study worked

Phase 2a double-blind, placebo-controlled, randomized adaptive Bayesian trial at University College London. 82 participants with cannabis use disorder were randomized to CBD 200mg, 400mg, 800mg, or placebo for 4 weeks. The 200mg dose was eliminated at interim analysis.

What this study cannot tell us

Small sample size (82 total). Short treatment duration (4 weeks). Single site. The adaptive Bayesian design, while efficient, means the 200mg dose was tested in fewer participants.

How to read the evidence

Strong: randomized, double-blind, placebo-controlled trial with innovative adaptive Bayesian design, though limited by sample size.

When this study was published

Published in 2020 in The Lancet Psychiatry.

The bigger picture

Using a non-intoxicating cannabis compound to treat cannabis addiction is a novel approach. The high completion rate (94%) and lack of severe side effects suggest CBD could be a practical treatment option worth pursuing in larger trials.

Questions still open

Would longer CBD treatment produce larger effects? Why did 400mg outperform 800mg? Would CBD help people with more severe cannabis dependence? What is the optimal duration of treatment?

Common questions

How does CBD help with cannabis addiction?

The exact mechanism is not fully understood, but CBD may reduce cannabis cravings and withdrawal symptoms without producing intoxication. In this trial, participants who took CBD used less cannabis and had more abstinent days than those on placebo.

Why did 400mg work better than 800mg?

The trial found 400mg slightly outperformed 800mg on both primary outcomes, suggesting a possible inverted U-shaped dose response. However, both doses exceeded efficacy thresholds, and the sample was too small to definitively establish which dose is optimal.

Read the original research

Cannabidiol for the treatment of cannabis use disorder: a phase 2a, double-blind, placebo-controlled, randomised, adaptive Bayesian trial.

The lancet. Psychiatry, 7(10), 865-874

View on PubMed ↗Publisher’s paper ↗

Citation

Freeman, Tom P; Hindocha, Chandni; Baio, Gianluca; Shaban, Natacha D C; Thomas, Emily M; Astbury, Danica; Freeman, Abigail M; Lees, Rachel; Craft, Sam; Morrison, Paul D; Bloomfield, Michael A P; O'Ryan, Dominic; Kinghorn, Jane; Morgan, Celia J A; Mofeez, Ali; Curran, H Valerie. (2020). Cannabidiol for the treatment of cannabis use disorder: a phase 2a, double-blind, placebo-controlled, randomised, adaptive Bayesian trial.. The lancet. Psychiatry, 7(10), 865-874. https://doi.org/10.1016/S2215-0366(20)30290-X