THE RELATION OF THE DOPAMINE TRANSPORTER GENE (DAT1) TO SYMPTOMS OF INTERNALIZING DISORDERS IN CHILDREN

The relation of the dopamine transporter gene (DAT1) to symptoms of in ternalizing disorders, Tourette's disorder, and obsessive-compulsive d isorder was examined using both within- and between-family tests of as sociation. The sample consisted of clinic-referred children.and their siblings and controls and their siblings. Between-family association w as examined via the association of DAT1 genotypes with disorder sympto ms in the population. Symptoms of all eight disorders increased with a greater number of 10-repeat DAT1 alleles. Using a quantitative transm ission disequilibrium test (QTDT), linkage and within-family associati on was indicated by increased symptoms in children who received 10 rep eat alleles from heterozygous parents relative to children who receive d 9 repeat alleles. Four disorders were associated with DAT1 using the QTDT: generalized anxiety, social phobia, obsessive-compulsive, and T ourette's. The effects of comorbidity were investigated by repeating t he same between- and within-family analyses on residual scores, with a ny effects of attention deficit hyperactivity disorder symptoms remove d. Although the residuals were associated less strongly with DAT1 than were the original scores, three disorders continued to show associati on both between and within families: generalized anxiety, Tourette's, and social phobia.