Period of Risk
Another challenging issue is the difficulty in identifying the onset of BD as well as transitions from other disorders, particularly MDD to BD, across the life span. Prospective data have demonstrated that there is a high risk of new episodes of mania emerging in late life.1 In their latter 50-year follow-up, Angst demonstrated that the risk of new-onset mania is constant across the life span, with new episodes even emerging after age seventy. This implies that the risk of misclassification of BD as MDD does not fall off with advanced age. At the other end of the life span, there has been substantial controversy about what symptoms constitute early forms of bipolarity, especially irritability49 and behavioral problems.50 Moreover, several longitudinal studies of youth in community samples show that episodes of BD in youth may be transient, rather than early manifestations of a lifelong disorder.42,51 Tijssen and colleagues41 showed that the persistence of symptoms, rather than their presence or absence, was the strongest predictor of transitions to clinically significant outcomes in early adulthood. The development of staging models of BD, similar to those for schizophrenia, that incorporate the full spectrum of BD may provide a more comprehensive approach to characterize the earlier manifestations of symptoms of mania and depression and their co-occurrence for follow-up studies.46 Recent evidence for the independence of the familial diatheses underlying domains of mania and depression52,53 and mania and psychosis,53 despite their strong association, also supports the value of distinguishing the course of these three domains in a dimensional fashion.