Discriminant validity of attention-deficit hyperactivity disorder.

OBJECTIVE: The primary purpose of this study was to assess the discriminant validity of attention-deficit hyperactivity disorder (ADHD) relative to well-defined groups of children with other psychiatric disorders.
METHOD: Clinic-referred patients diagnosed as having ADHD without any other comorbid diagnosis (N = 13), were compared with patients with only anxiety disorders (N = 20), disruptive disorders other than ADHD (N = 15), and nonreferred controls (N = 18) on measures of cognitive and academic functioning, as well as on objective measures of attention, impulse control, and activity level.
RESULTS: All three patient groups were found to have cognitive and academic achievement difficulties relative to controls. However, the ADHD group was found to be inattentive and impulsive relative to the other patient groups and the nonreferred controls. Objective measurement of activity level distinguished the ADHD group from controls but not from the other two patient groups.
CONCLUSIONS: These data support the diagnostic validity of a small subgroup of ADHD children (i.e., those without comorbid diagnoses) and demonstrates, that as a group, these children can be distinguished from patients with anxiety as well as other disruptive disorders on objective test measures.