New phenotype definition of attention deficit hyperactivity disorder in relatives for genetic analyses

The goal of the present investigation was to create a phenotype definition in relatives of probands that reflects a more genetic form of attention deficit hyperactivity disorder (ADHD). Logistic regression was applied to the first-degree relatives of ADHD and normal control probands to create a quantitative phenotype that combined information across psychiatric, cognitive, and demographic domains. Models were run separately in mothers, fathers, sisters, and brothers. Although there was some overlap between the variables retained in each model, no two models had exactly the same variables. Our results suggest that the use of fitted logits may be valuable as a potential index of caseness. Since different characteristics were included in different groups of relatives, our results suggest that gender and generation may moderate the expression of ADHD.