Abstract
INTRODUCTION: In clinical trials of drug treatments for women's sexual dysfunction, placebo responses have often been substantial. However, little is known about the clinical significance, specificity, predictors, and potential mechanisms of placebo response in sexual dysfunction. AIM: We aimed to determine the nature and predictors of sexual function outcomes in women treated with placebo for female sexual arousal disorder (FSAD). METHODS: We conducted a secondary analysis of data from the placebo arm of a 12-week, multisite, randomized controlled pharmaceutical trial for FSAD (N=50). We analyzed the magnitude, domain specificity, and clinical significance of sexual function scores at baseline, 4, 8, and 12 weeks (post-treatment). We examined longitudinal change in sexual function outcomes as a function of several baseline variables (e.g., age, symptom-related distress) and in relation to changes in sexual behavior frequency during the trial. MAIN OUTCOME MEASURE: Female Sexual Function Index total score. RESULTS: The magnitude of change at post-treatment was clinically significant in approximately one-third of placebo recipients. Effect sizes were similar across multiple aspects of sexual function. Symptom improvement was strongly related to the frequency of satisfying sexual encounters during treatment. However, the relationship between sexual encounter frequency and outcome varied significantly between participants. CONCLUSIONS: A substantial number of women experienced clinically significant improvement in sexual function during treatment with placebo. Changes in sexual behavior during the trial, more so than participant age or symptom severity at baseline, appeared to be an important determinant of outcome. Contextual and procedural aspects of the clinical trial may have influenced outcomes in the absence of an active drug treatment.