Abstract
Objective: To compare the global cognitive functioning and frontal lobe functioning of children with and without DSM-IV combined type Attention Deficit Hyperactivity Disorder (ADHD).
Method: Participants were 6 to 10 year old, clinic-referred children diagnosed with combined type ADHD, who were medication naïve; and an age (± 3 months) and sex matched group of children without behaviour problems. The performance of the two groups were compared on measures of intellectual functioning and tests designed to assess the functions of the frontal lobes (verbal and-non-verbal fluency, reasoning, problem solving, spatial working memory, attention).
Results: The children with ADHD obtained significantly lower Wechsler Intelligence Scale for Children-third edition IQ scores than controls and performed more poorly across the range of frontal lobe tests. Group differences on these tests were attenuated when IQ scores were included in the analyses as a covariate.
Conclusions: Children with combined type ADHD have mild to moderate global cognitive impairment together with some impairment of functions subserved by the frontal lobes. Longitudinal studies are required to determine if the deficit in global cognitive functioning is a primary deficit or secondary to the deficit in frontal lobe functioning. The importance of neuropsychological assessment and follow-up for children with ADHD is stressed. Study limitations relate to the generalizability of the findings and the absence of a psychiatric control group.
Notes
1Data collection for the current study began before the updated Conners scales became available.
2The 10 subtests used in the calculation of Full Scale IQ were used to calculate the raw IQ score.