Correlates of placebo reaction in an outpatient population.

Variables describing 113 outpatients of a mental health clinic were derived from a Placebo Test, the MMPI, a Symptom Check List, measures a response style, and a questionnaire containing historical and demographic information. Two highly reliable scales, the Placebo Effect Scale (PES) and the Side Effect Scale (SES) were derived from the Placebo Test and served as dependent variables. PES scores were inversely related to reporting symptoms and unrelated to measures of response style. SES scores were directly related to reporting symptoms and with several measures of response style. There was a curvilinear relationship between placebo response and reporting side effects. Implications of results for further research are presented.