Comorbidity in ADHD-children: effects of coexisting conduct disorder or tic disorder on event-related brain potentials in an auditory selective-attention task.

In children with attention-deficit hyperactivity disorder (ADHD) some deficits in auditory information processing seem to exist. Further, comorbidity of ADHD with conduct disorder (CD) and tic disorder (Tic) is quite common but not yet fully understood. Thus, we investigated the effects of these two disturbances, when combined with ADHD, on electrophysiological correlates of auditory information processing. An auditory selective-attention task was used, and temporal as well as frontal lobe sensitive event-related electrical brain activity indicators like mismatch negativity (MMN) and negative difference wave (Nd), as well as P300 were registered in four groups of children (healthy controls, ADHD-only, and combined ADHD + CD as well as ADHD + Tic; total number 42). Performance measures showed that ADHD + CD had a higher impact on errors and reaction times than ADHD + Tic. The MMN effect indicated that all ADHD groups showed lower MMN amplitudes compared to normals, but only the group with ADHD + CD suffered from a significant deficiency in automatic auditory information processing. Nd and P300 amplitudes showed no significant group differences. It may be assumed that neurodynamic sufficiency in ADHD-only and ADHD + Tic children seems to be similarly impaired while there might be a greater deficit in ADHD + CD.