Early development of comorbidity between symptoms of attention-deficit/hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD).

Attention-deficit/hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD) are among the most common childhood disorders and frequently co-occur. The present study sought to advance our understanding of how comorbidity between ADHD and ODD develops during the preschool years by testing a cross-lagged model that integrates 2 prominent models: the developmental precursor model and the correlated risk factors model. Participants were 199 children (107 boys) who took part in a longitudinal study of preschoolers with behavior problems. Parent reports of ADHD and ODD symptoms were collected annually from ages 3 to 6 and a family history interview was administered at age 3. In support of the developmental precursors model, ADHD symptoms predicted later argumentative/defiant symptoms. In support of the correlated risk factors model, family histories of ADHD and ODD/CD symptoms were correlated risk factors that uniquely predicted ADHD and anger/irritable symptoms in children. Results suggest that the correlated risk factors model may best explain the development of comorbidity between symptoms of ADHD and anger/irritability, whereas the developmental precursors model may better explain the development of comorbidity between symptoms of ADHD and argumentative/defiance.