Early childcare and physical aggression: differentiating social selection and social causation.

BACKGROUND: Some research findings have suggested that group day-care may be associated with an increased risk for physical aggression.
METHODS: Cross-sectional maternal questionnaire data from a representative sample of 3431 Canadian 2- to 3-year-olds were used to compare rates of physical aggression shown by children looked after by their own mothers and those attending group day-care. A family risk index (using occupational level, maternal education, size of sibship, and family functioning) was created to test whether any difference in physical aggression might reflect social selection rather than social causation.
RESULTS: Aggression was significantly more common in children looked after by their own mothers than in those attending group day-care. Strong social selection associated with family risk was found, not only in the sample as a whole, but even within the high-risk subsample. However, after taking social selection into account, physical aggression was significantly more common in children from high-risk families looked after by their own parents. No such difference was evident in the majority (84%) of children from low-risk families.
CONCLUSION: Insofar as there are any risks for physical aggression associated with homecare they apply only to high-risk families.