Third, there are overlaps in the locations identified by linkage results (Table 3). The confidence intervals for the position of loci found by linkage studies are notoriously broad (Roberts et al., 1999), so that overlaps between localizations often occur by chance. However, if we restrict analysis to a window of just 5 Mb, then five regions are repeatedly found: chromosome 11, 75–80 Mb (Breen et al., 2011, Zubenko et al., 2003), chromosome 15, 37–42 Mb (Zubenko et al., 2003, Camp et al., 2005), chromosome 15, 87–92 Mb (Breen et al., 2011, Holmans et al., 2004, Holmans et al., 2007, Levinson et al., 2007), chromosome 3, 4–9 Mb (Breen et al., 2011, Middeldorp et al., 2008), and chromosome 2, 64–68 Mb (Middeldorp et al., 2008, Schol-Gelok et al., 2010). This is partly, but not entirely, due to the large number of loci found in one study (Zubenko et al., 2003), a study that has attracted criticism (e.g., unusually low simulation-based LOD score thresholds reported for analyses without covariates [Levinson, 2006]), so we cannot come to any firm conclusions, but this result suggests that some of the signal may be true.
