Sibling aggregation for psychiatric disorders in offspring at high and lowrisk for depression: 10-year follow-up

Background. A unique way of determining patterns of parent-offspring transm ission of risk to affective disorders is to focus on aggregation within sib ling pairs. We attempt to extend our previous finding that sibling aggregat ion is notable for anxiety disorders in a 10-year follow-up of siblings at high and low risk for depression, by virtue of parental diagnosis. Methods. The sample, which included 173 unique sibling pairs in the high ri sk cohort, and 83 pairs in the low risk cohort, had been assessed using sem i-structured clinical interviews three times over a 10-year period, spannin g from childhood to adulthood. Sibling aggregation was quantified using pai rwise odds ratios. Results. Sibling aggregation in the high risk cohort was greater than aggre gation in the low risk cohort for anxiety disorders, especially those that emerged in childhood, and later co-morbid disorders, especially major depre ssive disorder and suicide attempts. Conclusions. Familial liability to affective disorders may be reflected mos t strongly by a developmental sequence of anxiety disorders in childhood fo llowed by later depressive and suicidal behaviour in adolescence and adulth ood.