The high-density microarray platform used in this study (2.1 million probes) provides good ascertainment of CNVs > 10 kb, a substantial improvement in sensitivity over earlier studies of schizophrenia and autism. De novo CNVs of intermediate size (10–100 kb) were detected a rate of 3/426 (0.7%) in controls and at a rate of 3/177 (1.7%) in schizophrenia and 5/185 (2.7%) in bipolar disorder. Based on these observations, intermediate-size CNVs may contribute to risk for these disorders; however, they occur in a small fraction (2%–3%) of cases, and the relative effect size is smaller than for large de novo CNVs. We conclude that a small fraction of the heritability in schizophrenia can be found among intermediate sized de novo structural variants.
