Electroencephalographic characteristics of ADHD subtypes

Attention Deficit Hyperactivity Disorder (ADHD as a neurodevelopmental disorder includes three subtypes predominantly inattentive (ADHD-I), predominantly impulsive/hyperactive (ADHD-H), and predominantly combined (ADHD-C) that has formed a heterogeneity disorder due to differences in pathology and syndrome. The aim of this study was to evaluate the EEG characteristics of ADHD subtypes.  

Subjects included 61 boys (7-12 years old, normal intelligence) with ADHD (ADHD-I, N= 25; ADHD-H, N=14 and ADHD-C, N=22) and 43 typically developing children (TDC). The groups were matched for IQ- and age. Children were investigated regarding Child Behavior Checklist and brain electrical activity during eyes closed resting state (i.e. EEG power in delta (1-4 Hz), Theta (4-8 Hz), alpha (8-12 Hz) and Beta (12-30Hz) frequency bands. Statistical analysis included a 2x2 factorial design by additive model.  

Theta / beta ratio was higher in all ADHD subtypes, especially the ADHD-I subtypes, compared to normal children. In addition, in the ADHD-I subtypes, theta activity was higher and beta activity was lower. No significant difference was found between the groups in delta and alpha activity.

According to this results, EEG markers can better distinguish the ADHD-I subtype, which can be explained within the framework of the maturational lag model of the central nervous system.