Affective Instability: Bipolar Disorder Versus Borderline Personality Disorder

Abstract

This chapter summarizes current knowledge on the relationship between affective instability in borderline personality disorder (BPD) and bipolar disorder (BD). Understanding this relationship may clarify the boundaries between bipolar disorder and BPD, which are now only partially understood. This chapter addresses the concept of affective instability and elements of the debate over the relationship between BPD and bipolar disorder. It addresses current research on the phenomenological differences between affective instability in each disorder. It also discusses the neurobiology of each disorder as it may pertain to affective instability. Case examples are presented demonstrating some of the difficulties clinicians may face in distinguishing different types of affective instability characteristic of each disorder. This chapter concludes by summarizing current findings on treatment for affective instability in BPD and bipolar disorder.