Aging and the structure and long-term stability of the internalizing spectrum of personality and psychopathology.

Structural psychopathology research has identified two broad factors--internalizing and externalizing--that account for comorbidity among many common mental disorders. Evaluating the utility of these factors for nosology, research, and treatment entails expanding beyond a cross-sectional understanding to how these factors evolve over time. We tested factorial invariance of internalizing in three age cohort groups--35 years and under (n = 1,729), 36-50 years (n = 2,719), and over 50 years (n = 2,601)--as well as the long-term stability of internalizing within individuals. Internalizing showed a notable degree of invariance between cohorts and within cohorts over time; long-term internalizing stability was equivalently moderate-to-high in each cohort.