If extreme variations in temperament predispose to greater risk of developing BD, affective temperaments may represent the most prevalent phenotypic expression of the genes underlying BD (55), with the genes being maintained in the population because they have favorable evolutionary properties and BD representing an aberration of the expression of these genes (3,6). The use of temperament measures to create more clinically and genetically homogenous subgroups of patients may aid in the identification of genes underlying BD susceptibility. The results of our analyses suggest that at least some measures of temperament may have utility in genetic studies of BD.
