In the mushroom study there was a control group of 6 subjects. These subjects were given methylphenidate, which is not exactly an inert substance. A lot of people would not tolerate such a chemical well. (In one study half the sample experienced disruptive side effects.) Given that there were only 6 subjects in the control group, negative reactions to methylphenidate could easily provide a basis for the conclusion that the observed differences between group differences are due to the controls getting sick! An an aside, I wonder about the positive effect of psychotherapy on PMS, which has in fact been documented. Also a placebo effect?