Behavioral Approach System and Behavioral Inhibition System sensitivities and bipolar spectrum disorders: prospective prediction of bipolar mood episodes.

OBJECTIVES Research has found that bipolar spectrum disorders are associated with Behavioral Approach System (BAS) hypersensitivity and both unipolar and bipolar depression are associated with high Behavioral Inhibition System (BIS) sensitivity, but prospective studies of these relationships are lacking. We tested whether BAS and BIS sensitivities prospectively predicted the time to new onsets of major depressive and hypomanic and manic episodes in bipolar spectrum individuals. METHODS We followed 136 bipolar II or cyclothymic and 157 demographically matched normal control individuals prospectively for an average of 33 months. Participants completed the BIS/BAS scales and symptom measures at Time 1 and semi-structured diagnostic interviews every four months of follow-up. RESULTS The bipolar spectrum group exhibited higher Time 1 BAS, but not BIS, scores than the normal controls, controlling for Time 1 symptoms. Among bipolar spectrum participants, high BAS sensitivity prospectively predicted a shorter time to onset of hypomanic and manic episodes, whereas high BIS sensitivity predicted less survival time to major depressive episodes, controlling for initial symptoms. CONCLUSIONS 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.