Bipolar disorder is both puzzling and fascinating because extreme contrasts in mood and behavior occur within the same individual. At some times, people with bipolar disorder exhibit euphoria, supercharged energy, and excessive goal striving, but on other occasions, they are sad, lethargic, and hopeless. Bipolar disorders form a spectrum of severity () from the milder Cyclothymia to Bipolar II to full-blown Bipolar I disorder (at least one manic episode; Goodwin & Jamison, 2007
). What explains the rollercoaster of highs and lows of mood, energy, interest, and confidence in individuals with bipolar spectrum disorders?
Fig. 1 The spectrum of bipolar disorders. Severity increases from Cyclothymia to Bipolar II disorder to Bipolar I disorder. Cyclothymia involves recurrent hypomanic and depressive episodes that do not meet diagnostic criteria for mania and major depression, (more ...)
The hypothesized functions of neurobiological systems provide a way to conceptualize associations between personality traits, behaviors, and various forms of psychopathology. One such system, the behavioral approach system (BAS), is thought to underlie incentive motivation and approach behavior (Gray, 1994
). Gray posited that the BAS is mediated by a set of interacting brain structures in the central nervous system that process and respond to stimuli associated with reward. Thus, the BAS is hypothesized to be a psychobiological system that integrates approach motivation, personality traits, and behavioral tendencies involved in goal-seeking and reward responsiveness.
We suggest that a hypersensitive BAS characterizes individuals with bipolar disorder. We hypothesize that in bipolar disorder, the BAS becomes dysregulated easily and thus is vulnerable to extreme fluctuations in activation and deactivation. Such excessive BAS activation and deactivation results in (hypo)manic and depressive symptoms, respectively.