Evaluation of rare SV and exonic variation in ASD is particularly advanced. In contrast, evaluation of common variation is far more limited (Figure 1a) and the published GWAS for ASD are small by current standards. 86–89 It is currently not possible to discern or dismiss a role for common genetic variation in risk for ASD. In our opinion, GWAS with larger samples are needed for ASD, given that detailed studies of rare variation currently explain a fraction of risk and that common variation plays a clear role in other psychiatric disorders. Indeed, there were few confident findings for GWAS of SCZ when the sample sizes were similar to those now available for ASD. Additional support for our recommendation for more GWAS is provided by Voineagu et al. who identified a gene expression module that had attenuated expression in post-mortem brain samples of individuals with ASD and which also had enrichment for GWAS signals. 90
