Aggregation of lifetime Axis I psychiatric disorders through age 30: incidence, predictors, and associated psychosocial outcomes.

Longitudinal data from representative birth cohorts on the aggregation of psychiatric disorders, or the cumulative number of unique diagnosed disorders experienced by persons within a circumscribed period, are limited. As a consequence, risk factors for and psychosocial implications of lifetime disorder aggregation in the general population remain largely unknown. This research evaluates the incidence, predictors, and psychosocial sequela of lifetime disorder aggregation from childhood through age 30. Over a 14-year period, participants in the Oregon Adolescent Depression Project (probands; N = 816) were repeatedly evaluated for psychiatric disorders and assessed with multiple measures of psychosocial functioning. First-degree relatives of probands (N = 2,414) were also interviewed to establish their lifetime psychiatric history. The cumulative prevalence of common lifetime psychiatric disorders for the proband sample was 71%. Three-quarters of all proband psychiatric disorders occurred among 37% of the sample, and 82% of all disorder diagnoses were made among persons who met criteria for at least one other lifetime disorder. Lifetime disorder aggregation in probands was predicted by lifetime psychiatric disorder densities among first-degree relatives and was related to heterotypic comorbidity patterns that included disorders from both internalizing and externalizing domains, most notably major depressive and alcohol use disorders. By age 30, disorder aggregation was significantly associated with mental health care service utilization and predictive of personality disorder pathology and numerous indicators of poor psychosocial functioning. Possible implications of disorder aggregation on the conceptualization of lifetime psychiatric disorder comorbidity are discussed.