An examination of the impact of attention-deficit hyperactivity disorder on IQ: a large controlled family-based analysis.

Objective: Although children with attention-deficit hyperactivity disorder (ADHD) have, on average, lower intelligence quotient (IQ) scores than control subjects, the reasons for these deficits remain unknown. Because IQ is highly familial, we investigated whether children with ADHD have a decrement in IQ from expectations based on parental IQ. Method: Subjects were 276 children with ADHD and 239 control subjects of similar age and sex. Expected IQ was calculated based on biological parents' estimated IQ. A significant discrepancy between observed and expected estimated IQ was defined by a child scoring 15 IQ points or more lower than expected, based on parental IQ. Results: Compared with control subjects, children with ADHD were significantly more likely to have lower than expected estimated IQ scores based on parental IQ, though this finding was accounted for by a small subgroup of children with ADHD who had an IQ15 points or more lower than expected, based on parental IQ. These children were more likely to be female, have higher psychopathological, neuropsychological, educational, and interpersonal deficits, as well as higher rates of perinatal complications. Conclusions: Group differences in IQ scores between children with and without ADHD reported in the literature may be accounted for by a subgroup of children with ADHD who have a large decrement in IQ from expectations based on parental IQ. Although perinatal complications may explain these findings, more work is needed to better understand the etiology of these IQ deficits. Objectif : Bien que les enfants souffrant du trouble de deficit de l'attention avec ou sans hyperactivite (TDAH) aient, en moyenne, des scores plus faibles de quotient intellectuel (Ql) que les sujets temoins, les raisons de ces deficits demeurent inconnues. Parce que le Ql est hautement familial, nous avons recherche si les enfants souffrant du TDAH ont une baisse du Ql que celui attendu a partir du Ql parental. Methode : Les sujets etaient 276 enfants souffrant du TDAH et 239 sujets temoins d'âge et de sexe semblables. Le Ql prevu etait calcule d'apres l'estimation du Ql des parents biologiques. Un ecart significatif entre l'estimation du Ql observe et prevu etait defini par un enfant dont le score de Ql etait de 15 points ou plus inferieur a ce qui etait prevu, selon le Ql parental. Resultats : Compares aux sujets temoins, les enfants souffrant du TDAH etaient significativement plus susceptibles d'avoir des scores de Ql estime plus faibles que prevu, selon le Ql parental, bien que ce resultat rende compte d'un petit sous-groupe d'enfants souffrant du TDAH qui ont eu 15 points ou plus de Ql inferieurs a ce qui etait prevu, selon le Ql parental. Ces enfants etaient plus susceptibles d'etre de sexe feminin, d'avoir des deficits psychopathologiques, neuropsychologiques, educatifs et interpersonnels plus eleves, ainsi que des taux plus eleves de complications perinatales. Key Words: attention-deficit hyperactivity disorder, children, intelligence quotient, deficits Conclusions : Les differences de scores de Ql entre les groupes d'enfants avec et sans TDAH mentionnees dans la litterature peuvent etre representees par un sous-groupe d'enfants souffrant du TDAH qui ont un vaste ecart de Ql par rapport a celui attendu a partir du Ql parental. Bien que les complications perinatales puissent expliquer ces resultats, il faut plus de travail pour mieux comprendre l'etiologie de ces deficits de Ql. Abbreviations ADHD attention-deficit hyperactivity disorder CBCL Child Behaviour Checklist CD conduct disorder DSM Diagnostic and Statistical Manual for Mental Disorders FES Family Environment Scale h2 heritably of IQ IQ intelligence quotient IQD IQ deficit IQ^sub E^ expected IQ IQ^sub F^ father's IQ IQ^sub mean^ mother's IQ IQ^sub mean^ mean IQ K-SADS-E Schedule for Affective Disorder and Schizophrenia for School Age Children - Epidemiologic Version LBW low birth weight MDD major depressive disorder SAICA Social Adjustment Inventory for Children and Adolescents SES socioeconomic status SUD substance use disorder WAIS-R Weschler Adult Intelligence Scale - Revised WISC-R Weschler Intelligence Scale for Children- Revised WRAT-R Wide Range Achievement Test- Revised Aspate of literature documents shows children with ADHD display lower IQ scores than control children. …