Effects of stimulant medications on the EEG of children with attention-deficit/hyperactivity disorder

Rationale: Stimulant medications are the most commonly used treatments for attention deficit/hyperactivity disorder (ADHD) in North America and Australia, although it is still not entirely known how these medications work. Objectives: This study aimed to investigate the effects of stimulant medications on the EEG of children with the Combined subtype of ADHD. Method: An initial EEG was recorded during an eyes-closed resting condition and Fourier transformed to provide absolute and relative power estimates for the delta, theta, alpha and beta bands. Theta/alpha and theta/beta ratios were also calculated. Subjects were placed on a 6-month trial of a stimulant and a second EEG was recorded at the end of the trial. Results: The ADHD group had significantly greater absolute delta and theta, less posterior absolute beta, more relative theta, and less relative alpha than the control group, which is typical of EEG studies of children with ADHD. The use of stimulant medications resulted in normalisation of the EEG, primarily evident in changes in the theta and beta bands. Conclusions: These results suggest that stimulants act to increase cortical arousal in children with ADHD, normalising their brain activity.