Lifetime rates of psychopathology in single versus multiple diagnostic assessments: comparison in a community sample of probands and siblings.

Lifetime prevalence rates of psychopathology vary a great deal depending on whether they are estimated from cross-sectional or prospective longitudinal studies, with the former yielding significantly lower rates. Such findings, however, come from comparisons of separate studies from different countries and cohorts. Here, we compare lifetime rates of psychopathology between a community sample of individuals assessed on multiple occasions to their siblings who completed only a single diagnostic evaluation. Data come from the Oregon Adolescent Depression Project. We included 442 original participants who completed four prospective diagnostic assessments over the course of fifteen years, and 657 of their siblings who completed a single lifetime assessment. Comparisons of rates of depressive, bipolar, anxiety, and substance use disorders were made using survival analysis. We found that rates of depressive disorders, specifically major depressive disorder, were elevated among individuals who completed multiple diagnostic assessments relative to individuals who completed a single lifetime assessment. We did not find significant differences in rates of aggregate anxiety, bipolar, or substance use disorders. Within a single cohort, cross-sectional surveys appear to underestimate the lifetime rates of major depression relative to prospective, longitudinal designs. This suggests that disorders with an episodic course may be under-reported in cross-sectional surveys. Rates of anxiety, bipolar, and substance use disorders did not differ across assessment methods. To further evaluate method effects on lifetime estimates of psychopathology, future work may benefit from comparing rates of retrospectively- and prospectively-derived diagnoses in individuals who are repeatedly assessed over a lengthy follow-up period.