A family study of early-onset bipolar I disorder

Background: Relatives of early-onset bipolar probands have greater risk for affective disorders than those of adult-onset bipolar probands. Methods: Relatives of 50 adolescent bipolar I probands and 36 adult-onset bipolar probands (onset ≥25 years) were assessed using the Family Interview for Genetic Studies (FIGS) by a qualified psychiatrist blind to the proband status. Morbid risk was calculated using Weinberg’s method of age correction. Results: Relatives of early-onset probands had significantly greater risk for affective disorders compared to the relatives of adult-onset bipolar probands. Conclusions: Early-onset bipolar disorder is more familial than the adult bipolar disorder. Implications: Subdivision of bipolar disorder according to age-at-onset may identify homogenous subtypes useful for genetic studies. Limitations: Patients were recruited from a major psychiatric hospital. The family history method was used to collect information about relatives.