We further reasoned that frequencies of de novo CNVs might be influenced by the presence or lack of a family history of mental illness, a hypothesis based on earlier findings by our group and others that de novo CNVs occur more frequently in sporadic cases of ASD (Marshall et al., 2008 and Sebat et al., 2007) and schizophrenia (Xu et al., 2008). We stratified subjects based on evidence of positive family history, defined as having a first-degree relative with a diagnosis of bipolar I, bipolar II, major depression, schizophrenia, schizoaffective disorder, autism, or intellectual disability. In BD and SCZ cohorts, rates of de novo mutation were not higher in sporadic cases as compared with subjects with a positive family history (Table S5).
