Observations of a similar nature have been made in studies of BD. CNV loci at 16p11.2 (McCarthy et al., 2009) and 3q29 (Clayton-Smith et al., 2010, Mulle et al., 2010 and Quintero-Rivera et al., 2010) confer risk for multiple psychiatric disorders, and two studies have found preliminary evidence implicating both in BD (McCarthy et al., 2009 and Quintero-Rivera et al., 2010). Two studies have demonstrated an enrichment of rare CNVs in patients with bipolar disorder (Priebe et al., 2011 and Zhang et al., 2009) as compared with healthy controls. In both studies, the greatest enrichment was observed in subjects with an earlier disease onset, defined as an age at onset (AAO) < 18 and < 21 in Zhang et al. (2009) and Priebe et al. (2011), respectively. However, two subsequent studies did not support these findings (Grozeva et al., 2010 and McQuillin et al., 2011). Thus, the role of copy-number variation in conferring risk for bipolar disorder remains in question (Grozeva et al., 2010 and Zhang et al., 2009).
