GAIN has also been the setting for the first GWAS in ADHD, which was carried out in 958 Caucasian case–parent-trios collected as part of the International Multicentre ADHD Genetics (IMAGE) study in children (Brookes et al. 2006; Kuntsi et al. 2006). Using the genotyping data from this study, Neale et al. (2008a) reported a classic transmission disequilibrium analysis (TDT) of a categorically defined ADHD phenotype. In addition, Lasky-Su et al. (2008b) performed an analysis using quantitative measures of ADHD symptoms. In the meantime, a second set of genome-wide data has been reported by Lesch and coworkers. These researchers used pools of DNA from 343 ADHD-affected adults and 304 controls for their genome-wide association analysis of a categorical ADHD phenotype (Lesch et al. 2008). Following the first analyses, the GAIN/IMAGE ADHD dataset has since been used for a number of exploratory studies using additional phenotypes and designs, like the age of onset of ADHD symptoms (Lasky-Su et al. 2008a), conduct problems (Anney et al. 2008b), and even a genome-wide gene–environment interaction (G × E) study evaluating genetic variants moderating the effects
