Increased prevalence and earlier onset of mood disorders among relatives of prepubertal versus adult probands

Objective: To compare the familial clustering of affective disorders among first-degree relatives of prepubertal versus adult probands with mood disorders. Method: The Family History-Research Diagnostic Criteria (FH-RDC) assessment instrument was used to obtain data on first-degree relatives of all probands. Logistic regression was used to assess the strength of the age of the proband to predict FH-RDC diagnoses in relatives. Survival analysis was used to examine the age-at-onset distribution of first FH-RDC diagnosis while controlling for year of birth. Results: The prevalence of major affective disorders was more than two times higher among first-degree relatives of child probands versus those of adult probands even when controlling for birth cohort. Cumulative risk for lifetime major mood disorders in first-degree relatives of child probands was significantly higher than for those of adult probands. Conclusion: These analyses further support that ascertainment of families through affected children identifies pedigrees with a higher proportion of affected relatives than ascertainment through affected adults.