To facilitate the interpretation of the many association findings in schizophrenia, a regularly updated online database of all published genetic association studies for schizophrenia (“SzGene”) has been created (http://www.schizophreniaforum.org/res/sczgene/default.asp). The group of researchers that set up the database has also performed meta-analyses in at least four independent case–control samples for all polymorphisms with available genotype data (Allen et al., 2008). Across 118 meta-analyses, a total of 24 genetic variants in 16 different genes (APOE, COMT, DAO, DRD1, DRD2, DRD4, DTNBP1, GABRB2, GRIN2B, HP, IL1B, MTHFR, PLXNA2, SLC6A4, TP53, and TPH1) showed nominally significant effects with average summary odds ratios of approximately 1.23. Using recently proposed criteria for the assessment of cumulative evidence in genetic association studies, the authors characterized four of the significant results, including DRD1, as showing “strong” epidemiological credibility.
