CBD for Scan Anxiety: The Primary and Secondary Comparisons Disagreed
A CBD scan-anxiety trial did not meet its primary endpoint, although a secondary comparison favored CBD. Reporting only the positive secondary finding would give an incomplete account of the randomized evidence.
One dose before a cancer-related scan
Fifty women with advanced breast cancer and baseline clinical anxiety were randomized equally to 400 mg oral CBD or placebo. Anxiety was assessed before and two to four hours after administration in the setting of an upcoming tumor-assessment scan.
The primary outcome compared changes in the afraid subscale of a validated mood scale between groups. That is a different calculation from comparing the groups’ final anxiety scores alone.
Change scores did not establish superiority
Mean anxiety change was −19.1 in the CBD group and −15.0 in the placebo group. The between-group primary comparison was not significant, with p = 0.37.
A separate comparison of post-dose anxiety levels favored CBD, with p = 0.02. These findings can coexist because baseline levels and the chosen statistical contrast affect the question being tested. A significant final-score comparison does not retroactively turn the primary change-score endpoint positive.
What the study supports
No grade 3 or 4 toxic effects were reported, but one dose in 50 participants cannot establish long-term safety or exclude uncommon adverse effects. The participants’ cancer stage, prior experiences and concurrent treatments also restrict generalization.
The findings justify further study of an acute anxiety signal rather than an unqualified claim that CBD treats cancer-related anxiety. This was a trial of a defined oral preparation and a defined stressor, not evidence that cannabis products broadly relieve every type of distress.
Related: How study design affects interpretation of CBD outcomes.
Primary research
Cannabidiol for Scan-Related Anxiety in Women With Advanced Breast Cancer: A Randomized Clinical Trial. JAMA Network Open (2024).
