Why the CBD Jaw-Pain Trial Assigned More Participants to Active Treatment
Unequal group sizes in the CBD jaw-pain trial were partly intentional: the protocol used two-to-one blocked randomization. More participants in the CBD group did not, by itself, show that random assignment had failed.
The allocation ratio was specified
The investigators generated randomized blocks of three with a 2:1 CBD-to-placebo allocation. They explained that the ratio allowed more participants to receive the potentially beneficial active treatment.
Among the fifty-four participants analyzed, thirty-five were in the CBD group and nineteen in the hemp-seed-oil group. Final analyzed counts need not be an exact two-to-one ratio after the study’s reported exclusions and follow-up issues.
Randomization is not synonymous with equal numbers
A randomized trial can deliberately use unequal allocation. The relevant issues are how the allocation sequence was generated, concealed and implemented, together with what happened after assignment.
The larger active-treatment group also does not guarantee comparable precision to a balanced trial of the same total size. The information available for a between-group contrast depends on both groups, along with outcome variability and missing observations.
The design choice does not alter the efficacy finding
The study did not demonstrate a statistically significant pain advantage for 20 mg daily CBD oil over hemp seed oil. Jaw function improved within both groups without significant between-group superiority. The allocation plan helps explain the participant counts; it is not evidence for efficacy or a basis for assuming that the smaller comparator group’s experience was unimportant. The small single-center study and its adherence procedures still limit interpretation.
Related analysis: the CBD jaw-pain trial’s pain and function results.
Research cited
Reeve and colleagues (2026), Oral Cannabidiol in the Treatment of Myofascial Pain Disorder of the Temporomandibular Region: A Placebo-Controlled Randomized Clinical Trial. DOI: 10.1159/000551040.
