Our findings have important clinical and research implications. First, our results emphasise that further investigation of CNVs in ADHD is a priority for research into this disorder. We do not suggest, however, that the search for common genetic variants using SNPs should be abandoned because, up to now, SNP-based studies1 have not had sufficient power to allow realistic assessment of the role of that class of variant in ADHD. Moreover, with the application of appropriate precautions such as we have undertaken, studies analysing SNPs and large, rare CNVs can be undertaken simultaneously. Key measures that allowed us to undertake such an analysis despite the use of two different SNP arrays were: that we limited our analysis to SNPs overlapping between platforms, we undertook quality-control checks in samples genotyped with both platforms, we validated the CNVs with independent platforms, and crucially, as our own cross-platform validation data show, we focused on CNVs large enough to be detected at high sensitivity and specificity irrespective of SNP array.
