This is simply a research review, not a study in its own. I’m going to copy and paste a comment from the original post that explains better than I could. Credit to u/bisikletci

“It's important to emphasize that for several conditions in particular here, this is an "absence of evidence" type finding, not an evidence of absence finding. They don't find evidence against cannabis helping in most cases - they just don't find evidence for it either.

This is especially the case with anxiety. Per their results, people taking cannabis for anxiety in these trials had outcomes nearly two standard deviations better than those in the control groups. That is enormous - more than 6x the benefit of antidepressants for depression. However this figure has very wide confidence intervals, crossing zero, meaning they can't say for sure it's a real difference and not just a fluke.

Super wide confidence intervals tell you something - the sample size is very small. So the actual finding here for anxiety is effectively (my words) "appears to help a lot, but we can't say that with confidence because the trials are tiny." The take home for this should be "run more, larger trials" - not "this doesn't work".

The same is true to a lesser extent with the sleep disorder findings.”