Illnesses in siblings of US patients with bipolar disorder relate to multigenerational family history and patients severity of illness

- Compared to Europeans, siblings of bipolar patients from the US are more ill.
- Positive family history of psychiatric problems breeds true into the siblings.
- Adverse characteristics in bipolar patients predict psychiatric problems in siblings.
- Multigenerational family burden in the US suggests the need for new interventions.

BackgroundPatients with bipolar disorder from the US have more early-onset illness and a greater familial loading for psychiatric problems than those from the Netherlands or Germany (abbreviated here as Europe). We hypothesized that these regional differences in illness burden would extend to the patients siblings.MethodsOutpatients with bipolar disorder gave consent for participation in a treatment outcome network and for filling out detailed questionnaires. This included a family history of unipolar depression, bipolar disorder, suicide attempt, alcohol abuse/dependence, drug abuse/dependence, and “other” illness elicited for the patients' grandparents, parents, spouses, offspring, and siblings. Problems in the siblings were examined as a function of parental and grandparental problems and the patients' adverse illness characteristics or poor prognosis factors (PPFs).ResultsEach problem in the siblings was significantly (p<0.001) more prevalent in those from the US than in those from Europe. In the US, problems in the parents and grandparents were almost uniformly associated with the same problems in the siblings, and sibling problems were related to the number of PPFs observed in the patients.LimitationsFamily history was based on patient report.ConclusionsIncreased familial loading for psychiatric problems extends through 4 generations of patients with bipolar disorder from the US compared to Europe, and appears to “breed true” into the siblings of the patients. In addition to early onset, a variety of PPFs are associated with the burden of psychiatric problems in the patients' siblings and offspring. Greater attention to the multigenerational prevalence of illness in patients from the US is indicated.