The impact of restrictive entry criterion during the placebo lead-in period.

In the study of depression, most randomized clinical trials have design features that attempt to sample from a stable patient population. One commonly used design feature is to require patients to maintain some minimum baseline symptom severity score during a placebo lead-in period. One intent of this design feature is to evaluate the behavior of patients prior to administration of active medication. If, during the lead-in period, patients do not maintain minimum symptom severity, the patients are excluded from the remainder of the study, the theory being that the excluded patients are not part of a stable patient population and hence are not likely to demonstrate efficacy of a truly effective treatment. This presentation investigates the effectiveness of a restrictive entry criterion and proposes an alternative explanation for what is usually defined as placebo response.