Age and sex effects in the EEG: differences in two subtypes of attention-deficit/hyperactivity disorder

Objectives: This study investigated age-related changes and sex differences in the EEGs of two groups of children with attention-deficit/hyperactivity disorder (ADHD) combined type and ADHD predominantly inattentive type, in comparison with a control group of normal children. Methods: Forty boys and forty girls were included in each group. The EEG wa s recorded during an eyes-closed resting condition and Fourier transformed to provide estimates for total power, absolute and relative power in the de lta, theta, alpha and beta bands, and for theta/alpha and theta/beta ratios . Results: Total power, relative alpha, and the theta/alpha and theta/beta ra tios were differentiated between all 3 groups. Sex differences between the ADHD subjects and the control group were greater in males than females and matured faster in males. With increasing age, the EEG of the ADHD inattenti ve group was found to change at a similar rate to the changes found in the normal group, with the differences in power levels remaining constant. In t he ADHD combined group, the power was found to change at a greater rate tha n in the ADHD inattentive group, with power levels of the two ADHD groups b ecoming similar with age. Conclusions: These results are supportive of a two-component model of ADHD, with the hyperactive/impulsive component maturing with age and the inatten tive component remaining more stable. (C) 2001 Elsevier Science Ireland Ltd . All rights reserved.