SHANK2 and attention deficit-hyperactivity disorder: Thus, the above-cited ADHD sample size may not give sufficient power to identify a larger pool of loci associated with ADHD, which perhaps could include SHANK2. Furthermore, as mentioned above, the majority of the participants of these GWAS were from European-ancestry populations with relatively few ethnic Chinese samples by comparison (Li et al., 2014; Demontis et al., 2019).