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Bipolarity from an Evolutionary Angle

Ronald Mellen and Wade C. Mackey

Published: 2009/12/01

Abstract

Medical practitioners and behavioral scientists may often analyze the same behavior from quite different perspectives. Medical practitioners tend to focus on an individual — a patient — and will intervene to cure or heal any perceived insult to the body of that patient. Behavioral scientists are more apt to view the same behavior or condition through the lens of central tendency wherein individual profiles are minimized. There is virtually no attempt to intervene on behalf of an individual to alleviate his or her distress. The behavioral scientist more focuses upon antecedent conditions and correlatives. As a complement to the medical model, bipolarity (or manic-depressive disorder) is examined in this article from an evolutionary viewpoint. This examination suggests that, within a population, the unfolding of a typical or normative process such as mood variations would be expected to generate dysfunctions for a small percentage of individuals. That is, normal variation would be expected to produce a small percentage of extreme cases of mood swings. Such expected extreme cases may prove dysfunctional for the affected individual or the social group or both. Gender differences which are in evidence in the prevalence of unipolarity (major depression), but not in bipolarity, are suggested to reflect differences in the two genders’ evolutionary trajectories.

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