Figure 1 shows the number of times that each gene or its protein product co-occurred with schizophrenia in a paper indexed by PubMed per year. This serves as a rough metric for the importance/impact of a gene for the schizophrenia research community. For eight genes, the numbers of studies increased with time (APOE, BDNF, CHRNA7, COMT, DISC1, DRD2, HTR2A, and NRG1). Four genes peaked and then tapered off (DAO, DAOA, DTNBP1, and RGS4). For 13 genes, there have been relatively few reports (AKT1, DRD3, DRD4, GRM3, KCNN3, MTHFR, NOTCH4, PPP3CC, PRODH, SLC6A3, SLC6A4, TNF, and ZDHHC8).
