This study investigated the relation of overweight/obesity with HTR2C –759C>T, ABCB1 1236C>T, ABCB1 2677G>T/A, and ABCB1 3435C>T polymorphisms in children and adolescents with ASD treated with risperidone. This evidence concerns the gene ABCB1 and obesity due to melanocortin 4 receptor deficiency.