Reward and Punishment Sensitivity and Emotion Regulation Processes Differentiate Bipolar and Unipolar Depression

Bipolar disorder (BD) and major depressive disorder (MDD) cannot be reliably differentiated by depression symptom expression alone, suggesting a need to identify processes that may more effectively differentiate the two disorders. To explore this question, currently depressed adults with BD (n?=?30) and MDD (n?=?30), and healthy control participants with no history of psychiatric illness (CTL; n?=?30), completed self-report measures of reward and punishment sensitivity (i.e., behavioral activation and inhibition) and emotion regulation processes (i.e., rumination and avoidance). Results revealed that constructs putatively linked to depression across the mood disorders (i.e., behavioral inhibition, negative rumination, dampening of positive affect, behavioral and experiential avoidance) were significantly higher in both mood disorder groups compared to CTLs. Yet there was also some specificity between mood disorder groups, such that the BD group reported significantly greater reward responsiveness and positive rumination, in addition to greater behavioral inhibition and avoidance, compared to the MDD group. These data suggest that patterns of affective responding previously linked to underlying risk for mania in BD may remain evident during a major depressive episode. Further, current models of reward sensitivity in BD may benefit from the inclusion of punishment sensitivity and behavioral avoidance, particularly with respect to bipolar depression.