Patient-Reported Symptom Relief Following Medical Cannabis Consumption

"On average, higher pre-dosing symptom levels were associated with greater reported symptom relief"

Of course they are. And of course, lower initial levels are associated with lower change scores. It's called regression to the mean. It will always bias any analysis involving paired change scores unless models include the initial value, or a paired t-test is performed. I hope they have not made this beginner's mistake, but it's not entirely clear from the methods that the correct adjustment was made. In fact, I get the impression that they think change scores are unbiased - which they most definitely are not.

Final gripe: there is no adjustment for multiple comparisons. Sigh.

/r/science Thread Link -