In the first systematic study of de novo CNVs in schizophrenia, Xu et al. observed a high rate in sporadic cases (10%) as compared with “familial” cases (defined as having an affected first or second degree relative) and a high rate compared with controls (Xu et al., 2008). Subsequent studies by Kirov et al. (Kirov et al., 2011) and by our group (Malhotra et al., 2011), also observed a high rate of de novo CNVs in schizophrenia (5% in both studies) as compared with controls; however, neither study observed a significant difference in rate between in sporadic and famial cases.
