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 defic its in auditory information processing seem to exist. Further, comorbidity of ADHD with conduct disorder (CD) and tic disorder (Tic) is quite common b ut 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 wa s used, and temporal as well as frontal lobe sensitive event-related electr ical brain activity indicators like mismatch negativity (MMN) and negative difference wave (Nd), as well as P300 were registered in four groups of chi ldren (healthy controls, ADHD-only, and combined ADHD + CD as well as ADHD + Tic; total number 42). Performance measures showed that ADHD + CD had a h igher impact on errors and reaction times than ADHD + Tic. The MMN effect i ndicated that all ADHD groups showed lower MMN amplitudes compared to norma ls, but only the group with ADHD + CD suffered from a significant deficienc y in automatic auditory information processing. Nd and P300 amplitudes show ed no significant group differences. It may be assumed that neurodynamic su fficiency in ADHD-only and ADHD + Tic children seems to be similarly impair ed while there might be a greater deficit in ADHD + CD.