different ascertainment biases for each disorder. An example of a difference in ascertainment methods is that ID studies include data from clinical referrals, whereas CNV data are acquired for schizophrenia generally only in the research setting where it may be difficult to ascertain the most severely affected patients. These biases need to be considered carefully and in theory could have contributed to a broadening of the ID diagnostic group; however, we suspect that these potential biases are unlikely to impact the major findings of our study that emphasize the vast degree of loci sharing across these disorders. In follow-up studies to this one when sample sizes get even larger, there may be a dimension to this sort of analysis whereby the frequency of a given CNV in a disorder is considered as opposed to simply the categorical association alone which was the subject of the current analysis. Finally, the high degree of overlap across disorders is clear in this study for these most common among the rare, large CNVs; however, it is possible that as sample sizes reach hundreds-of-thousands, we may observe very rare CNVs (frequency approximately 1/10,000 or less), and subsequently the distribution of these very rare CNVs across
