The 2018 Cochrane review reported similar remission percentages with CBD-containing capsules and placebo, but a wide confidence interval. Similar observed percentages did not establish that the treatments were equivalent.
What the review reported
Seven of 29 participants receiving the cannabinoid preparation achieved remission at ten weeks, compared with eight of 31 receiving placebo. The risk ratio was 0.94, with a 95% confidence interval from 0.39 to 2.25. The review rated this evidence low certainty.
The preparation contained CBD and some THC. The estimate should not be presented as a trial of every CBD product or of a chemically pure CBD isolate.
A near-one estimate can remain uncertain
A risk ratio of one represents equal risks on this scale. The reported interval extended well below and above that value, leaving substantial uncertainty about the true comparative remission effect. Failure to demonstrate superiority is different from demonstrating equivalence within a prespecified clinically acceptable margin.
The appropriate clinical-research conclusion
This small trial did not establish a remission benefit, and its uncertainty cannot be converted into proof that cannabinoids work exactly as well as placebo. The historical review also does not supply an individual probability of recovery. Keep the endpoint, time point, formulation and confidence interval attached when evaluating a treatment claim.
Related reading: why endpoint definitions matter.
Research cited
Kafil and colleagues (2018). Cannabis for the treatment of ulcerative colitis. DOI: 10.1002/14651858.CD012954.pub2.
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