Latent class and factor analysis of DSM-IV ADHD: A twin study of female adolescents

Objective: In an attempt to validate the current DSM-IV criteria for attention-deficit/hyperactivity disorder (ADHD) in females and to determine whether symptoms are continuously distributed or categorically discrete, the authors performed factor and latent class analysis on ADHD symptom data from a large general population of adolescent female twins (1,629 pairs). Method: A structured diagnostic assessment of DSM-IV ADHD was completed with at least one parent of 1,629 pairs by telephone. ADHD symptoms from 1,549 pairs were subjected to latent class and factor analysis. Results: Latent class and factor analyses were consistent with the presence of separate continuous domains of inattention (ATT), hyperactivity-impulsivity (H-I), and combined ATT with H-I problems. Severe latent classes corresponding to the predominantly inattentive, predominantly hyperactive-impulsive, and combined types were identified with lifetime prevalence estimates of 4.0%, 2.2%, and 3.7%, respectively. Membership in the severe ATT class predicted academic problems, family problems, and referral to health care providers. Membership in the H-I and combined classes also predicted impaired social relationships. Conclusions: These results suggest that DSM-IV ADHD subtypes can be thought of as existing on separate continua of inattention, hyperactivity- impulsivity, and combined type problems. Membership in any of the three severe ADHD latent classes did not preclude academic excellence, but it was associated with different types of impairment and health care-seeking behavior. These data have implications in the areas of diagnosis, classification, treatment, and research.