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 there 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.