The purpose of this study was to see if the clinical outcome of stimulant medication (methylphenidate) in pediatric Attention Deficit Hyperactivity Disorder can be predicted on the bases of changes in Event Related Potentials (ERPs) induced by a single dose of stimulant medication. (ERPs are extracted from electroencephalographic (EEG) registrations during the performance of an attention task).

In the pediatric neuropsychiatric clinic of Ostfold Hospital Trust, Norway, patients diagnosed with attention deficit hyperactivity disorder are tested with quantitative EEG (QEEG) and ERPs to supplement the neuropsychological examination. In the majority of cases a systematic four weeks trial on stimulant medication is offered, and the clinical effects are evaluated at the end of the try-out period. This procedure is a clinical routine. In this study patients and parents were asked if they were willing to complete a second QEEG/ERP test on a single dose of stimulant medication shortly before the onset of the four weeks trial. They were explained that the aim of the study was to search for predictors of clinical response. They were also informed that this second test was completely voluntary. (In fact the vast majority were quite enthusiastic). The patients were characterized as responders (REs - medication continued) or non-responders (non-REs - medication stopped) based on explicit criteria. The single-dose induced changes in ERPs (and behavioral parameters from the attention test; number of errors, reaction times) were examined, and differences between REs and non-REs were calculated.

If the analysis of data show that one or several variables are significantly different in REs and non-REs with large effect sizes, these findings may eventually result in the development of a useful clinical tool.

Inclusion Criteria:

• Patients referred to the clinic diagnosed with Attention Deficit Hyperactivity Disorder. Cases With comorbid diagnoses such as emotional or behavioral disorders, learning disabilities or high functioning autism are included.

Exclusion Criteria:

• Patients With intelligence coefficients below 70 or a diagnosed neurological disease are excluded.