Discrimination of DSM-IV and latent class attention-deficit/hyperactivity disorder subtypes by educational and cognitive performance in a population-based sample of child and adolescent twins.

OBJECTIVE: Despite the general use of DSM-IV attention-deficit/hyperactivity disorder (ADHD) subtypes, there is controversy over the optimal phenotyping strategy for this disorder.This report contrasts two ADHD subtyping approaches on the prediction of cognitive function and educational achievement.
METHOD: ADHD subtypes were determined using DSM-IV and latent class approaches for a population sample of 1,154 child and adolescent twins using parent report data. Twins completed cognitive and achievement testing and parents reported on school grades, special education placement, and history of being held back in school.
RESULTS: The DSM-IV primarily inattentive and combined subtype ADHD groups showed significant deficits in cognitive and achievement testing, worse grades, and increased use of special education resources compared with the primarily hyperactive/impulsive subtype and no-ADHD groups. Clinically relevant and less severe latent class ADHD subtypes were also associated with deficits in cognitive and achievement testing, grades, and special education use.
CONCLUSIONS: DSM-IV primarily inattentive and combined subtypes of ADHD have similar significant patterns of cognitive and academic dysfunction in the general population. Latent class-defined ADHD subtypes also have patterns of serious cognitive and achievement deficits.