LD mapping studies have identified plausible positional candidate genes in regions of linkage or of cytogenetic abnormalities associated with psychiatric disorders, and these genes have suggested new mechanistic hypotheses. (20) For example, as of April, 2008, there were 1291 published studies of 690 schizophrenia candidate genes (see http://www.schizophreniaforum.org/res/sczgene/default.asp). A recent meta-analysis of these studies (3) identified four “strong” psychiatric candidate gene associations based on epidemiological criteria for meta-analysis, but not at what is currently understood to be a genomewide level of statistical significance (see below).
