Developmental pathways to bipolarity: are juvenile-onset depressions pre-bipolar?

This article approaches the question of bipolarity in childhood and adolescence from an "adult" perspective. It argues that clinically ascertained juvenile depressions--with onsets typically in late childhood or early adolescence--have affinity to bipolar spectrum disorders based on (1) early age at onset; (2) even gender ratio; (3) prominence of irritability, labile moods, and explosive anger indicative of mixed episodes; (4) high rates of "comorbid" substance abuse; (5) questionable response to antidepressants and/or brief hypomanic switches; (6) high rates of recurrence; (7) familial affective loading; and (8) frequent superposition on affective temperamental dysregulation. Building on the last point, the author submits that dysthymic, cyclothymic, and hyperthymic temperaments represent putative developmental pathways to bipolarity (as contrasted to "inhibited" anxious-phobic types, which appear related to nonbipolar outcomes.