Consistent with the BAS hypersensitivity model of bipolar disorder, a highly responsive BAS provides vulnerability to onsets of (hypo)manic episodes. In addition, a highly sensitive BIS increases risk for major depressive episodes.

In recent years, a call for increased research on bipolar disorder has been answered with methodologically diverse studies exploring goal striving, life events, cognitive style, decision-making, and neurobiological abnormalities in bipolar disorder. In order to further this spurt of research and to systematize our understanding of bipolar disorder, an integrative perspective is warranted. The behavioral approach system (BAS) dysregulation theory, proposed by Richard Depue and colleagues, provides such an integrated model for understanding psychosocial and biological aspects of bipolar disorder. In this paper, we review studies on life events, cognitive style and other psychosocial and neurobiological factors to examine whether the BAS dysregulation theory is supported by existing data. Then, we draw on recent advances in the study of emotion and motivation, and propose an expansion of the BAS dysregulation model of bipolar spectrum disorders to foster further biopsychosocial investigations of bipolar disorder. This expanded model provides greater specificity in predictions, especially about the nature of BAS dysregulation, environmental factors and psychological processes (e.g., appraisal processes) featured in a causal chain culminating in bipolar symptoms. Finally, we discuss the implications of the expanded BAS model for the course of bipolar spectrum disorders.

Little longitudinal research has examined progression to more severe bipolar disorders in individuals with “soft” bipolar spectrum conditions. We examine rates and predictors of progression to bipolar I and II diagnoses in a non-patient sample of college-age participants (n = 201) with high General Behavior Inventory scores and childhood or adolescent onset of “soft” bipolar spectrum disorders followed longitudinally for 4.5 years from the Longitudinal Investigation of Bipolar Spectrum (LIBS) project. Of 57 individuals with initial cyclothymia or bipolar disorder not otherwise specified (BiNOS) diagnoses, 42.1% progressed to a bipolar II diagnosis and 10.5% progressed to a bipolar I diagnosis. Of 144 individuals with initial bipolar II diagnoses, 17.4% progressed to a bipolar I diagnosis. Consistent with hypotheses derived from the clinical literature and the Behavioral Approach System (BAS) model of bipolar disorder, and controlling for relevant variables (length of follow-up, initial depressive and hypomanic symptoms, treatment-seeking, and family history), high BAS sensitivity (especially BAS Fun Seeking) predicted a greater likelihood of progression to bipolar II disorder, whereas early age of onset and high impulsivity predicted a greater likelihood of progression to bipolar I (high BAS sensitivity and Fun-Seeking also predicted progression to bipolar I when family history was not controlled). The interaction of high BAS and high Behavioral Inhibition System (BIS) sensitivities also predicted greater likelihood of progression to bipolar I. We discuss implications of the findings for the bipolar spectrum concept, the BAS model of bipolar disorder, and early intervention efforts.

Adolescence is a period of radical normative changes and increased risk for substance use, mood disorders, and physical injury. Researchers have proposed that increases in reward sensitivity, i.e., sensitivity of the behavioral approach system (BAS), and/or increases in reactivity to all emotional stimuli (i.e., reward and threat sensitivities) lead to these phenomena. The present study is the first longitudinal investigation of changes in reward (i.e., BAS) sensitivity in 9 to 23-year-olds across a two-year follow-up. We found support for increased reward sensitivity from early to late adolescence and evidence for decline in the early twenties. This decline is combined with a decrease in left nucleus accumbens (Nacc) volume, a key structure for reward processing, from the late teens into the early twenties. Furthermore, we found longitudinal increases in sensitivity to reward to be predicted by individual differences in the Nacc and medial OFC volumes at baseline in this developmental sample. Similarly, increases in sensitivity to threat (i.e., BIS sensitivity) were qualified by sex, with only females experiencing this increase, and predicted by individual differences in lateral OFC volumes at baseline.