Evidence for a genetic etiology in hyperactivity in children.

There has been considerable controversy over the nosology of hyperactivity and attention deficit hyperactivity disorder (ADHD). There have been suggestions that genetic influences may play a role in the origins of individual differences on this dimension or dimensions of behavior and that an understanding of the significance of genetic factors might help to clarify the classification of these disorders. Multiple regression is used to analyze data from a sample of 91 pairs of identical twins and 105 pairs of same sex fraternal twins. The heritability of extreme group membership (h2g = 0.75) was significant for activity rated by the mother. The heritability for one of the measures of attention deficit was also significant (h2g = 0.76). The results are consistent with a significant genetic contribution to individual differences in activity levels and attention abilities.