Association Between Early Childhood Aggression and Internalizing Behavior for Sibling Pairs

Objective: This article investigates sibling similarity in early childhood problem behavior.

Method: Analyses are based on an Australian longitudinal study of health and development that included sister, brother, and mixed-sex sibling pairs. Pregnant women were recruited into the study in 1981 to 1983 and provided information regarding family characteristics and child behavior from birth through the age of 5 years. The relationship between older and younger siblings' aggression and internalizing behavior at the age of 5 years is examined, based upon maternal reports on a shortened version of the Child Behavior Checklist for 414 sibling pairs (60% of the initial sibling sample).

Results: The results demonstrate a moderately strong association between sibling's aggression and internalizing behavior, for mixed- and same-sex siblings, with correlation coefficients of 0.26 to 0.39. The association between older and younger sibling's behavior remains significant, controlling for family characteristics such as mother's age, mental health, marital status, affection toward children, and family size and income.

Conclusions: The findings highlight the importance of including siblings in family-based intervention programs aimed at reducing child behavior problems.