[gus_massa]

The problem with "they subjectively report feeling better" is that sometimes the people "lie" voluntary or involuntary. Perhaps they don't feel better but want to make the experimenter happy. Perhaps they don't feel better but wish to feel better. Too much possible sources of confusion.

Just using an exaggeration for comparison, if you pay $1000000 to the experiment subject in one arm to say that they fell better, then you will get a very big improvement, but it doesn't mean that they really feel better. This is an exaggeration, but the problem is that there are a lot of more subtle things that can change the self reported feeling.

I don't know how to measure the well feeling in a non subjective way. If I may just made up an inexistent medical device, perhaps I can put a 24hs endorphin measurer to the test subject and look for a difference in the mean concentration.