et al. 2004; Asherson et al. 2008; Bakker et al. 2003; Hebebrand et al. 2006; Ogdie et al. 2003; Ogdie et al. 2004; Ogdie et al. 2006; Romanos et al. 2008; Zhou et al. 2008a), and recently also using ADHD endophenotypes at the level of neuropsychological functioning (Doyle et al. 2008; Rommelse et al. 2008c). Although linkage designs have been highly successful in the identification of genes for monogenic diseases, this has not been the case for polygenic or multifactorial disorders. The linkage studies in ADHD have identified a number of genetic loci (potentially) harboring genes for ADHD, but very little overlap was observed between studies, so far. A recent meta-analysis of ADHD linkage studies only confirmed one locus, on chromosome 16 (Zhou et al. 2008c).
