We selected 25 genes prominent in the pre-GWAS era. The first schizophrenia GWAS appeared in 2007 but, given that many candidate gene association studies were published in 2008, we evaluated candidate gene studies published in calendar year 2008 or earlier. The 25 genes we selected were either featured in reviews of the genetics of schizophrenia 10, 12–14 or were highly studied (≥20 papers recorded in SZGene). The genes and the rationale for being a candidate gene for schizophrenia are given in Table 1. We continued several important assumptions made by virtually all candidate gene studies (see Limitations). First, these studies evaluated “schizophrenia” as a dichotomous entity. Second, as with the primary studies, we assumed that genetic variants act on the gene it was in or near. This assumption is crucial and will be inaccurate for a currently unknown proportion of genetic variants. Third, as discussed below, almost all of these studies evaluated common genetic variation.
