Common single nucleotide polymorphisms (SNPs) are currently, in addition to structural variants, convincing risk factors for schizophrenia and bipolar disorder, with alleles at more than 20 loci reported to show genome-wide significant association with at least one of the disorders11-29. None of these low-risk variants are located inside structural polymorphisms previously shown to be susceptibility factors for schizophrenia or bipolar disorder. Nevertheless, first principles and data from other disorders predict the existence of common variants conferring risk through the same genes as rare structural alleles30. The identification of common risk variants within CNV regions may aid in uncovering the causal gene or genes of a CNV, or help to elucidate other aspects of a CNV’s association with disease.
