Developmental evaluation of family functioning deficits in youths and young adults with childhood-onset bipolar disorder

•We examined family functioning in youths and adults with childhood-onset bipolar disorder (BD).•Family functioning was worse in participants with BD vs. healthy controls, regardless of demographics.•There was no influence for mood, global functioning, comorbidity, and most medications.•Removing those taking lithium showed a significant diagnosis-by-age interaction.•Youths with BD had worse family problem solving and communication relative to healthy controls. Childhood-onset bipolar disorder (BD) is a serious condition that affects the patient and family. While research has documented familial dysfunction in individuals with BD, no studies have compared developmental differences in family functioning in youths with BD vs. adults with prospectively verified childhood-onset BD. The Family Assessment Device (FAD) was used to examine family functioning in participants with childhood-onset BD (n = 116) vs. healthy controls (HCs) (n = 108), ages 7–30 years, using multivariate analysis of covariance and multiple linear regression. Participants with BD had significantly worse family functioning in all domains (problem solving, communication, roles, affective responsiveness, affective involvement, behavior control, general functioning) compared to HCs, regardless of age, IQ, and socioeconomic status. Post-hoc analyses suggested no influence for mood state, global functioning, comorbidity, and most medications, despite youths with BD presenting with greater severity in these areas than adults. Post-hoc tests eliminating participants taking lithium (n = 17) showed a significant diagnosis-by-age interaction: youths with BD had worse family problem solving and communication relative to HCs. Limitations include the cross-sectional design, clinical differences in youths vs. adults with BD, ambiguity in FAD instructions, participant-only report of family functioning, and lack of data on psychosocial treatments. Familial dysfunction is common in childhood-onset BD and endures into adulthood. Early identification and treatment of both individual and family impairments is crucial. Further investigation into multi-level, family-based mechanisms underlying childhood-onset BD may clarify the role family factors play in the disorder, and offer avenues for the development of novel, family-focused therapeutic strategies.