Personality disorders and mood disorders: perspectives on diagnosis and classification from studies of longitudinal course and familial associations.

The results of three rigorous studies of the naturalistic course of personality disorders indicate the following: (1) personality psychopathology improves over time at unexpectedly significant rates; (2) particular maladaptive personality traits are more stable than personality disorder diagnoses; (3) although personality psychopathology improves, residual effects are usually seen in the form of persistent functional impairment and ongoing Axis I psychopathology; and (4) improvement in personality psychopathology may eventually be associated with reduction in ongoing personal and social burden. A comparison of the longitudinal stability of personality disorders and mood disorders does not support a clear distinction between them based on differential stability of either psychopathology (at least based on remission rates) or functional impairment. Differences may yet emerge with respect to relapse rates over the longer term. Both types of disorders may share some common underlying vulnerabilities best conceptualized in term of personality traits. A group of promising, though methodologically flawed, family studies suggest familiality of at least BPD among the personality disorders and the coaggregation of BPD and depressive disorders (but not bipolar disorders) that may contribute to their frequent co-occurrence. Again, underlying personality traits may prove to be more heritable than either type of disorder.