Drinking Fell in Both Groups: What Two Placebo-Controlled CBD Trials Found

forensic toxicology working group members October 28, 2026 Forensic Toxicology

Alcohol consumption fell substantially in both CBD and placebo groups in two proof-of-concept trials. Neither trial demonstrated CBD superiority. Within-group improvement should not be reported as a treatment effect when the randomized comparison does not support it.

Two related populations

One trial randomized 27 adults with alcohol use disorder to CBD or placebo over eight weeks, increasing CBD from 600 to 1200 mg daily halfway through treatment. A second randomized 30 adults with alcohol use disorder and PTSD or subthreshold PTSD to 600 mg daily or placebo for six weeks.

The primary drinking outcome was average drinks per day. Craving and psychiatric symptoms were also assessed.

Exposure was documented, benefit was not established

CBD was absorbed, with pharmacokinetic findings showing exposure and dose-related increases. Both groups improved substantially on drinking measures, but CBD did not outperform placebo on drinking, craving, mood, anxiety or PTSD symptoms.

This is not evidence that no participant benefited. It means the trials did not establish an incremental benefit attributable to CBD under their tested conditions.

Tolerability needs its numerator

Seven of the 31 participants assigned to CBD across the studies experienced dose-limiting side effects. Describing the regimen as feasible or generally tolerated should include that finding.

The studies were small, so uncertainty remains around effect sizes, doses and subgroups. Funding included public research support and Tilray Canada. These limitations justify further research; they do not turn a null randomized comparison into a positive one.

For an evidence review, separate the change from baseline, the difference from placebo and the achieved exposure. Each addresses a different part of the causal question.