jim_asheville 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. Worth answering the question that was asked rather than the one behind it. The narrow version usually has an answer; the broad version usually does not, and answering the broad one is how a thread stops being useful.

The figures, for anyone assembling their own picture. One habit that pays for itself: post the method alongside the number. A figure without its method cannot be checked, and an unchecked figure is how this community accumulates folklore.

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

How long did you give it before you decided it was working?

Dr.RaviCardio said:

One habit that pays for itself: post the method alongside the number.

This is where I part company with the consensus forming above. Pushing back on the anecdote-stacking. Twenty people reporting the same thing is twenty samples from the same self-selected pool, not twenty independent confirmations.

Dr.RaviCardio said:

One habit that pays for itself: post the method alongside the number.

That is right, and it stops being right at the edges. The general case is well behaved; the interesting cases in this thread are all at the boundary where the general case breaks.