Psychological treatment versus nonspecific factors: A meta-analysis of conditions that engender comparable expectations for improvement

Abstract Meta-analysis was used to compare the effectiveness of psychological treatment to both nonspecific factors control (NSF) and no treatment control conditions in studies in which no significant differences were found in subjects' expectancies for improvement between treatment and NSF control conditions. Treatment was found to be more effective than well designed NSF control, and more effective than no treatment. Nonspecific factors conditions were also found to be more effective than no treatment. Psychological treatment was found to be approximately twice as effective as well-designed NSF conditions. Analyses of study characteristics showed that greater treatment effects (treatment versus no treatment comparisons) were found in studies that were conducted in non-university rather than university settings, that used non-students rather than college students as subjects, and that used a mixture of professionals and graduate students compared to graduate students as therapists.