relevance to the BDII subtype based on clinical and prospective data showing high sensitivity and specificity of cyclothymic lability for BDII (9,43). Interestingly, one study reported high heritability estimates for the hyperthymic (50.9%, p<0.001) and irritable (74.8%, p<0.001) temperaments in 31 extended Caucasian families with BD, whereas the dysthymic temperament was moderately heritable (29.2%, p<0.05), and the cyclothymic temperament was not significantly heritable (26). It may thus be that the hyperthymic and irritable temperaments provide more power for gene identification within the context of BD.
