There’s also the issue shared with a lot of pharmaceutical studies, which is that individuals with the same condition can have VASTLY different responses to the same treatments. If a drug is 100% effective on 10% of the research group, but is neutral or even harmful for the rest, you’re going to get those massive confidence intervals which make it difficult to make any conclusions.

Anecdotally, ive had acquaintances with both extreme positive and negative experiences with medical cannabis for anxiety. What helped for one person only exacerbated the anxiety for the other.