Relationship of birth cohort and early age at onset of illness in a bipolar disorder case registry

Objective: Utilizing data from a previously characterized registry of subjects with bipolar illness, the authors examined age at onset of the first illness episode in cohorts of subjects born from 1900 through 1939 and from, 1940 through 1959. Method: Demographic and clinical characteristics at the first full episode of bipolar disorder of subjects in a diagnostically validated voluntary bipolar disorder registry (N=1,218) were reviewed and subjected to statistical analyses. Results: The median age at onset of the first episode of bipolar illness was lower by 4.5 years in subjects born during or after 1940 (median age=19 years), compared with subjects born before 1940 (median age=23.5 years). The proportion of subjects with bipolar disorder presenting with a prepubertal onset was significantly higher in the later birth-year cohort than in the earlier birth-year cohort. More than 50% of male and female subjects in both cohorts had a depressive episode as the first episode of bipolar illness. Subjects in each cohort who had a parent with major depression, bipolar disorder, or schizophrenia experienced their first episode nearly 4 to 5 years earlier than the other subjects in the cohort. Conclusions: Prospective epidemiological studies conducted with bipolar disorder subjects are needed to either affirm or refute these data on age at illness onset. If the results are affirmed, the early recognition of prepubertal bipolar disorder will be important, so that the condition can be treated with appropriate medications and medications that could potentially worsen the illness course can be avoided. Similarly, early recognition of bipolar illness is important, especially in women, to minimize use of antidepressant monotherapy for patients with bipolar illness. Among young people presenting with major depression as the first illness episode, a parental history of major depression, bipolar disorder, or psychosis may be a useful pointer to future bipolar disorder. Early recognition and appropriate treatment of bipolar illness may prevent the development of chronicity and serious functional impairment.