Diagnostic Precursors to Bipolar Disorder in Offspring of Parents With Bipolar Disorder: A Longitudinal Study

Objective: The authors sought to identify diagnostic risk factors of manic, mixed, or hypomanic episodes in the offspring of parents with bipolar disorder ("high-risk offspring"). Method: High-risk offspring 6-18 years old (N=391) and demographically matched offspring (N=248) of community parents without bipolar disorder were assessed longitudinally with standardized diagnostic instruments by staff blind to parental diagnoses. Follow-up assessments were completed in 91% of the offspring (mean follow-up interval, 2.5 years; mean follow-up duration, 6.8 years). Results: Compared with community offspring, high-risk offspring had significantly higher rates of subthreshold mania or hypomania (13.3% compared with 1.2%), manic, mixed, or hypomanic episodes (9.2% compared with 0.8%), and major depressive episodes (32.0% compared with 14.9%). They also had higher rates of attention deficit hyperactivity disorder (30.7% compared with 18.1%), disruptive behavior disorders (27.4% compared with 15.3%), anxiety disorders (39.9% compared with 21.8%), and substance use disorders (19.9% compared with 10.1%), but not unipolar major depressive disorder (major depression with no bipolarity; 18.9% compared with 13.7%). Multivariate Cox regressions showed that in the high-risk offspring, subthreshold manic or hypomanic episodes (hazard ratio=2.29), major depressive episodes (hazard ratio=1.99), and disruptive behavior disorders (hazard ratio=2.12) were associated with subsequent manic, mixed, or hypomanic episodes. Only subthreshold manic or hypomanic episodes (hazard ratio=7.57) were associated when analyses were restricted to prospective data. Conclusions: Subthreshold manic or hypomanic episodes were a diagnostic risk factor for the development of manic, mixed, or hypomanic episodes in the offspring of parents with bipolar disorder and should be a target for clinical assessment and treatment research. Major depressive episodes and disruptive behavior disorders are also indications for close clinical monitoring of emergent bipolarity in high-risk offspring.