Study subjects’ responses to placebo have increased from an average two-point decline in symptom ratings in studies done from 1991 to 1998, to an average decline of 7 points in studies done between 1999 and 2008.
Related item:
FDA tracks rising impact of the ‘placebo effect’ in antipsychotic trials
This is a very interesting observation! Could it be an artifact of the trial design? When people start a trial on antipsychotics they are usually on another antipsychotic. They have to go abruptly off their previous medications while they are thinking that they’re getting the new medication in the so-called placebo washout trial, usually for 2 weeks. Then the real trial starts and excremental group gets the real drug and the control group continues on placebo.
The experimental group will of course get many side effects that may be visible to the researchers, but it may be that the placebo group nowadays, as they are probably coming off second-generation anti psychotics have so many withdrawal effects that it is more difficult for researchers to guess who is in the experimental group and who is in the control group.
In this way it’s not that easy for them to break the blind as they might have done in the past, guessing on the basis of side effects.
So maybe this is just a testimony to how withdrawal effects of the second-generation anti psychotics may be much worse than withdrawal effects from first-generation anti psychotics. The researchers are not able to break the blind, they think a patient in the placebo group has got the “real stuff” , and since they are paid by the manufacturer, they will consciously or unconsciously score this person as more improved than if they thought the patient had got placebo.