As mentioned above, most of the GWAS data so far are derived from one sample of child–parent triads collected as part of the IMAGE study. IMAGE is a consortium of researchers from seven European countries and Israel. IMAGE has ascertained more than 1,400 families through a (preferentially combined subtype) ADHD-affected proband (Brookes et al. 2006; Kuntsi et al. 2006). The probands were required to be in the age range from 5 to 17 years. All families were of European Caucasian descent. In all families, both parents and at least one sibling, the latter not selected for phenotype, were required to take part in the study. IMAGE participants were extensively phenotyped for ADHD and comorbid disorders, using the Parental Account of Childhood Symptoms (PACS) (Taylor et al. 1986), administered by centrally trained investigators. In addition, rating scale measures were used, including the Long Version of Conners’ Parent and Teacher Rating Scales, as well as the parent and teacher version of the Strength and Difficulties Questionnaires (SDQ) (Conners 2003). A standardized algorithm was applied to PACS to derive each of the 18
