The investigators did not plan a multiple-testing adjustment across the many different outcomes. Secondary signals should therefore remain distinct from a confirmatory finding on the primary motor endpoint.
The trial specified a primary question
The study compared CBD/THC with placebo for change in motor MDS-UPDRS score. It also examined numerous motor, nonmotor, safety and exploratory outcomes. The authors described the other outcomes as descriptive or exploratory and stated that adjustment across different outcome variables was not planned.
The primary between-group motor comparison was nonsignificant. Within-group improvement in the active arm did not supply the missing superiority result.
More comparisons create more opportunities for a signal
When many outcomes are examined, an isolated conventional p value needs context. This does not mean that every secondary finding is false or that unfavorable outcomes may be discarded. It means their evidentiary role differs from a prespecified confirmatory test with appropriate control of the comparison family.
Report direction and uncertainty together
Some reported sleep, cognition and daily-function outcomes favored placebo. They warrant attention alongside adverse events while retaining the brief trial, small sample and multiple comparisons. A balanced summary should neither promote a selected favorable scale as established efficacy nor present every exploratory signal as a separately confirmed treatment effect.
Related reading: exposure evidence and driving impairment.
Research cited
Liu and colleagues (2024). Short-term cannabidiol with delta-9-tetrahydrocannabinol in Parkinson disease: a randomized trial. DOI: 10.1002/mds.29768.
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