Background: Although (hypo)manic symptoms are common in adolescence, transition to adult bipolar disorder is infrequent.
Aims: To examine whether the risk of transition to bipolar disorder is conditional on the extent of persistence of subthreshold affective phenotypes.
Method: In a 10-year prospective community cohort study of 3021 adolescents and young adults, the association between persistence of affective symptoms over 3 years and the 10-year clinical outcomes of incident DSM-IV (hypo)manic episodes and incident use of mental healthcare was assessed.
Results: Transition to clinical outcome was associated with persistence of symptoms in a dose-dependent manner. Around 30-40% of clinical outcomes could be traced to prior persistence of affective symptoms.
Conclusions: In a substantial proportion of individuals, onset of clinical bipolar disorder may be seen as the poor outcome of a developmentally common and usually transitory non-clinical bipolar phenotype.