Problem behavior in early and middle childhood: an initial behavior genetic analysis.

Twin samples were used to estimate the relative importance of genetic and environmental influences on problem behavior in children, assessed by the Child Behavior Checklist (CBCL). For the younger cohort, mothers completed the CBCL/2-3, while for the older cohort the CBCL/4-18 was used. Nearly half of the older sample had also been assessed with the questionnaire for younger children at a prior date, providing tentative answers regarding continuity and change in the etiology of problem behavior. Results suggested that shared environmental influences may be more important in early childhood than in middle childhood, while the reverse holds for genetic influences.