Hypomania: a depressive inhibition override defense mechanism.

OBJECTIVE Evolutionary perspectives on bipolar disorders can further our understanding of the origins of these conditions, and assist clinicians in distinguishing normal from abnormal states. Hypomania is unique amongst bipolar conditions in that it seems to have beneficial aspects and can be difficult to diagnose, in contrast to full-blown mania and depression. A theoretical perspective regarding the evolution of hypomania as a defense mechanism is presented. METHOD Literature review focused on the fitness reducing aspects of depression and the fitness enhancing aspects of hypomania/mania. RESULTS Of all the adversity inherent in depression, inhibition of physical and mental activity-depressive inhibition-has the most detrimental consequences, and throughout our evolution would have significantly reduced fitness. It is proposed that hypomania evolved as a depressive inhibition override defense mechanism, typically operating in a short-term time frame, to restore physical and mental activity to fitness sustaining or enhancing levels. Over-activity and not mood enhancement enabled hypomania to function as a defense mechanism against the fitness reducing state of depressive inhibition. Contributing to depressive inhibition are the Behavioral Activation System (BAS) and the Behavioral Inhibition System (BIS), two basic motivational systems. Depressive inhibition consists to some extent of low BAS and high BIS. As human intelligence evolved cognitions inhibiting BAS and activating BIS became amplified, resulting in intensified depressive inhibition. LIMITATIONS A theoretical perspective. CONCLUSIONS Given its ability to override depressive inhibition hypomania might be viewed as a natural treatment as opposed to a problem to treat, producing maximal improvement in areas where functioning has suffered the most while typically enhancing social behavior.