Nocebo effects and psychotropic drug action

The role of psychosocial context around patient and therapy can be studied through randomized clinical trials. The analysis of the results of clinical trials, and considering the adverse events (AEs) in the placebo groups, provides an important perspective of study for this phenomenon. In double-blind, randomized clinical trials, the side effects reported in placebo-treated groups are not associated with pharmacological treatment, but other factors should be taken into account to explain these symptoms. This phenomenon may be conceptualized as ‘nocebo effects’ relating to negative expectations for treatment outcome, even though a role of prior learning in the form of conditioning with active treatments cannot be excluded. This approach makes it possible to observe how associating the placebo groups with a particular drug can cause specific AEs that are consistent with those observed in the active group. This phenomenon was described in a systematic review that examined placebo AEs in tricyclic antidepressant randomized clinical trials. The authors depicted nocebo effects in antidepressant placebos similar to the AE profiles of the real drugs, which they were matched with. These key findings contrast with the belief that nocebo effects were simply nonspecific. Moreover, they emphasize the need to develop standardized procedures for collecting information about AEs in randomized, double-blind, placebo-controlled trials determining drug efficacy.