Table 2 lists results from those meta-analyses of candidate genes for susceptibility to schizophrenia that found evidence of a positive genetic association. The summary presented suggests that genetic effects are small. The average odds ratio for the associations is 1·2, equivalent to ∼0·2% of the phenotypic variance, a figure consistent with that obtained from meta-analyses of other complex traits (Ioannidis et al. 2001).
