Symptomatic volunteers in depression research: a closer look.

Seventy-nine carefully screened volunteers were compared with 46 clinically referred outpatient primary depressives to assess the validity of use of symptomatic volunteers in research on depression. Overall, symptomatic and clinical referral samples were similar on the majority of demographic and symptomatic variables, although volunteers were less likely to be single, had slightly lower Hamilton scores, less self-reported anxiety, and a longer index episode of depression. Symptomatic volunteer and clinical referral groups had a similar prevalence of endogenous depression by either RDC or DSM-III criteria. Results in 60 patients treated with amitriptyline indicated that both groups were comparable with respect to overall dropout rate, side-effect attrition, dosage of amitriptyline received, and clinical response. Only the proportion of patients who dropped out between completion of assessment and initiation of treatment significantly differed between groups (symptomatic volunteers = 19%; clinical referrals = 0%; p less than 0.05). These findings support use of rigorously screened symptomatic volunteers in outpatient depression research.