How Do Affective Temperaments Develop Into Bipolar Disorders?

Affective temperaments are considered to be antecedents or sub-syndromal manifestations of bipolar disorders. It is, however, unknown how these temperaments develop into bipolar disorders. We hypothesize that: [1] just before the onset of bipolar disorder, the left medial frontal gyrus (MFG) of cyclothymic and/or hyperthymic healthy subjects may degenerate and shrink in volume concomitantly with its dysfunction, [2] just after the onset of bipolar disorder, this change may involve the right MFG and bilateral anterior cingulate cortex, leading to dysfunction of prefrontal cortex, [3] during the first episode of bipolar disorders, prefrontal dysfunction may involve limbic system, leading to dysfunction of prefrontal-limbic system, and [4] along with recurrences of bipolar disorders, the prefrontal-limbic system dysfunction may progress. On the basis of our neuroimaging findings of affective temperaments, we believe that these hypotheses warrant further investigation.