Controlecondities in klinisch interventieonderzoek

Randomized controlled trials (RCTs) often assume an unchanging control condition. When blinding is not feasible, waitlist or standard-care conditions can evoke negative expectations and nocebo effects. Differences between the intervention and control conditions are therefore determined not only therapeutically, but also contextually. Psychopathology and various somatic conditions are increasingly understood as disturbances of a complex dynamic system, in which small changes can trigger large shifts. Effects that may appear to be of little significance, such as the impact that assignment to a control condition has on people’s expectations, may have major effects on the outcome.

Conflict of interest and financial support: ICMJE forms provided by the authors are available online along with the full text of this article.