CBD Treatment for Cannabis Use Disorder Did Not Broadly Improve Cognition
Four weeks of CBD did not improve the prespecified delayed-memory outcome in a trial of cannabis use disorder. A positive finding on one working-memory task did not establish broad cognitive enhancement.
A secondary analysis of an existing trial
The cognitive report analyzed 70 participants assigned to placebo, 400 mg CBD daily or 800 mg CBD daily. An additional 200 mg group had been dropped at an interim stage of the parent trial and was not included in this analysis.
These participants intended to stop cannabis use and had moderate or severe cannabis use disorder. This report shares the parent trial’s participants; it is not an independent replication of the trial’s findings about cannabis consumption.
The main cognitive contrast was null
Delayed prose recall did not show a significant CBD-versus-placebo treatment-by-time effect at either analyzed dose. Most secondary cognitive outcomes were also null.
Backward digit span improved with 800 mg CBD, with a reported estimate of 0.30 and a confidence interval from 0.02 to 0.58. Forward digit span and other tasks did not show the same pattern. Manipulating information in working memory therefore should not be equated with global memory recovery.
What the isolated positive finding means
The study analyzed a fixed existing sample, limiting power for small effects and the ability to plan a new cognitive-specific sample size. Cannabis-use changes, practice effects and the selected treatment-seeking population also belong in interpretation.
A task-specific signal can justify replication without overturning the primary cognitive null result. Claims about improved attention, everyday functioning or safe driving require evidence for those outcomes. This study provides a useful distinction between treating cannabis use disorder and demonstrating a separate cognitive benefit.
Related: Interpreting CBD treatment outcomes.
Primary research
Effect of four-week cannabidiol treatment on cognitive function: secondary outcomes from a randomised clinical trial for the treatment of cannabis use disorder. Psychopharmacology (2023).
