Longitudinal studies of personality disorders: four lessons from personality psychology.

The three longitudinal projects described in this special section of the Journal of Personality Disorders raise a number of intriguing questions concerning the natural history of personality disorders and offer more than their share of surprises. In addition, they underscore several valuable lessons derived from the literature on normal-range personality traits. Drawing in part from the writings of the American trait psychologist Gordon Allport, I describe four such lessons: (1) change and continuity of personality traits and disorders can and do coexist, (2) the covariation among personality traits helps to account for the "comorbidity" among personality disorders, (3) personality traits and disorders influence how individuals interpret life events, and (4) personality traits must be distinguished from behavioral adaptations to these traits. These lessons remind us that the science of personality disorders must be informed by the basic science of personality.