Patients excluded from an antidepressant efficacy trial

Background: The impact of exclusion criteria on antidepressant trials is rarely investigated and poorly understood. We describe specific reasons for exclusion from a double-blind comparative trial and analyze the selection procedure and its impact on treatment outcome. Method: A 6-week randomized double-blind trial for depressive disorders recruited patients through outpatient psychiatric services, private offices, and health care centers. Of the 612 consecutive patients interviewed for a diagnosis according to DSM-III-R, 209 (34%) finally entered the trial. Results: 86% of the included patients had no comorbid psychiatric disorder, whereas a third of those excluded had at least one (p < .00001). Patients were excluded for having chronic alcohol or drug misuse (17%), receiving antidepressant drugs (15%), or having physical problems precluding their ability to take either of the drugs studied (14%). Some patients could not be included because of a referral to other modes of treatment (19%) or organizational difficulties (16%). The excluded patients less often suffered from major depressive disorder than those who were included in the trial. In particular, patients excluded because of suicidal thoughts or intent more often had a history of previous major depressive episodes (p = .006) compared with the included patients. The most important sociodemographic factors related to exclusion from the trial were male sex and unmarried status. Conclusion: Patients with previous depressive episodes or comorbid disorders were more likely to be excluded from the antidepressant efficacy trial. Data on the efficacy of antidepressant drugs on this patient population are still only infrequently obtained.