The theoretical underpinnings of affective temperaments: implications for evolutionary foundations of bipolar disorder and human nature

Abstract

We sketch out putative evolutionary roles for affective temperaments within the theoretical framework of mood disorders conceptualized as extremes in an oligogenic model of inheritance, whereby the constituent traits in their dilute phenotypes confer adaptive advantages to individuals and/or their social group. Depressive traits, among other functions, would subserve sensitivity to the suffering of other members of the species, overlapping with those of the generalized anxious temperament, thereby enhancing the survival of not only kin but also other conspecifics. The pursuit of romantic opportunities in cyclothymia suggests that it may have evolved as a mechanism in reproductive success; cyclothymics' creative bent in poetry, music, painting, cooking or fashion design (among men, in particular) also appears useful for sexual seduction. Hyperthymic traits would lend distinct advantages in leadership, exploration, territoriality and mating. These are just some of the possibilities of the rich and complex temperamental traits subserving bipolarity within an evolutionary framework. We test selected aspects of these hypotheses with the use of correlations between the constituent traits of the Temperament Evaluation of Memphis, Pisa, Paris and San Diego (TEMPS) and correlations between the TEMPS and the Temperament and Character Inventory (TCI). Such data support the counterbalancing protective influence of harm avoidance on the risk-taking behavior of cyclothymic individuals, in both men and women. Finally, we outline a hypothesis on the evolutionary function of anxious-depressive traits for women.