Problems with a diagnostic depression interview in a postpartum depression trial.

Background: Diagnostic and Statistical Manual (DSM) IV-based depression interviews, valued for their diagnostic accuracy, are often considered to be essential for depression treatment trials. However, this requirement can be problematic because of participant burden. The purpose of this article is to describe our experience with the depression component of the Structured Clinical Interview for DSM Disorders (SCID) in a postpartum depression treatment trial.

Methods: In this prospective cohort study of 506 mothers of infants from 7 primary care clinics, participants were asked to complete the depression module of the SCID interview soon after enrollment. They were asked to complete the 9-item Patient Health Questionnaire (PHQ-9) depression survey at 0 to 1, 2, 4, 6, and 9 months postpartum.

Results: Forty-five women (8.9%) had a positive SCID interview and 112 (22.1%) had a positive PHQ-9 during 0 to 9 months postpartum. Problems encountered when using the SCID depression interview included (1) lower than expected SCID-based rates of depression diagnosis (8.9%); (2) SCID noncompletion by 75 women (14.8%); SCID noncompleters (vs completers) were younger, poorer, less educated, and more likely to be single and black (vs white); and (3) inconsistent SCID/PHQ-9 results. Nineteen women with moderately severe to severe PHQ-9 score elevations (≥15) had negative SCID scores; all of these women were functionally impaired. More than 90% of women with positive PHQ-9 scores reported some degree of impairment because of their depressive symptoms.

Conclusions: The requirement of a diagnostic depression interview resulted in selection bias and missed opportunities for depression diagnosis; these are problems that detract from the interview's key strength-its diagnostic accuracy. These problems should be considered when electing to use a DSM-IV-based depression interview in research.