james_edin said:

The honest answer is that the effect is real, the magnitude is contested, and the individual variation is larger than either.

Adding the part of the answer the thread has not reached. The useful move here is to separate what is established from what is widely repeated. Those two sets overlap less than the confident tone of most write-ups suggests, and the second set is where nearly all the disagreement on this board comes from.

Adding the numbers, since they settle part of this. If you are going to change something, change one thing and give it long enough to express itself. Four weeks is the usual minimum for anything pharmacological on this board, and two weeks of data has told you almost nothing.

Following on from james_edin — and this may be the naive question:

How would you tell the difference between that and the alternative explanation?

dave_SLC said:

If you are going to change something, change one thing and give it long enough to express itself.

I do not accept the framing. The question has been narrowed to the version that has a tidy answer, and the part that was dropped is the part the OP actually asked about.

dave_SLC said:

If you are going to change something, change one thing and give it long enough to express itself.

Agreeing with dave_SLC, and the qualification matters more than the agreement. Yes, and the corollary is less popular: if the reasoning holds, it also holds where it produces an answer we do not like.