The factor structure of ADHD items in DSM-III-R: Internal consistency and external validation

Previous research employing factor-analytic procedures to study the underlying dimensions of DSM-III attention deficit disorder with hyperactivity (ADDH) symptoms have consistently supported a two-factor model. Revision of the structure of the ADHD diagnosis in DSM-HI-R, as well as inclusion of new items, has raised the question of comparability of the two diagnoses. To explore the significance of these changes, teacher ratings of DSM-III ADDH items and DSM-III-R ADHD items of 85 nonreferred school children were factor-analyzed to determine their underlying factor structures. A similar two-factor solution was obtained for each diagnostic scale. The factors consisted of items believed to reflect inattention and hyperactivity-impulsivity constructs. These factors were further evaluated against results of a cognitive test battery to ascertain whether objective, external validation could be demonstrated. The hyperactivity-impulsivity factor scores were related to continuous performance test measures of response inhibition, while inattention-disorganization factor scores were related to measures of attention and visual search. Implications for assessment and diagnosis of ADHD are discussed.The authors gratefully acknowledge the assistance of Sister Hildegarde Koger, the St. Francis de Sales School, and the parents and children who participated in this study.