Factor structure of symptom dimensions in attention-deficit/hyperactivity disorder (ADHD).

There is disagreement on whether attention-deficit/hyperactivity disorder (ADHD) symptoms are best characterized along two dimensions consisting of inattention and hyperactivity/impulsivity or three dimensions where hyperactivity and impulsivity are separate. To address this, the current study investigated the underlying symptom dimensions of ADHD by examining two- and three-factor models of ADHD symptom ratings in 400 children and adolescents diagnosed with ADHD. ADHD symptom ratings for each of the 18 DSM-IV Criteria A symptoms were obtained from mothers using a standardized symptom rating scale. Confirmatory factor analysis (CFA) was used to examine whether the 18 symptoms were best explained by two or three latent constructs. Results of the CFA demonstrated that a three-factor model was superior to a two-factor model. Findings support three distinct symptom dimensions that are consistent with previous research demonstrating unique clinical presentations of inattention, hyperactivity, and impulsivity. Differentiating between these three domains may aid in predicting behavioral outcomes in children with ADHD.