Affective instability: toward an integration of neuroscience and psychological perspectives.

Affective instability is a prominent feature of a wide variety of psychiatric and neurological disorders, yet it has not been systematically studied. It encompasses a number of distinct phenomena, including: (1) frequent affective category shifts, (2) disturbances in affect intensity, (3) excessively rapid emotion rise-times, (4) delayed return to emotional baseline, (5) excessive reactivity to psychosocial cues, (6) endogenously driven, random, chaotic or rapid-cycling changes, and (7) overdramatic expression. To further clarify the construct of affective instability, this article examines the manifestations of affective instability in a range of psychiatric and neurologic disorders, reviews relevant neurobiological and psychological emotion regulatory processes, and considers the psychology of affective instability.