The first paper on the GAIN/IMAGE ADHD genome-wide dataset was based on the 909 complete family triads, for which full genotyping information was available (Neale et al. 2008a). Of these families, 790 contained male probands, 119 female probands. A total of 845 probands had a combined subtype ADHD diagnosis, the average number of symptoms was 16.1. The TDT design was chosen for this study which contained families recruited from all over Europe and from Israel, based on its robustness against population stratification. Earlier research by Neale et al. (2008b) had shown that differences indeed existed between the different genetic backgrounds of the IMAGE participants, especially with the Israeli families of European Caucasian descent. In addition, the family controlled design showed more stability in the presence of non-random genotyping error in GAIN (Anney et al. 2008a). No genome-wide significant results were observed (with the highest P values at 7.45E-06), although a power analysis presented in the paper suggests that the size of the dataset would have been sufficient to detect at least one genome-wide significant (P value 5.0E-08) finding for a
