CACNA1C and schizophrenia: In fact, the largest schizophrenia GWAS to date found SNPs in three genes (CACNA1C, ITPR3 and CYP2D6) within the serotonergic synapse pathway reached GWAS significance (P<5 × 10−8) and SNPs in another 17 genes within this pathway were nominally significant (P<1 × 10−5).2 Furthermore, a recent gene-set enrichment analysis of the SZGene database25 identified 24 pathways significantly enriched for schizophrenia candidate genes among which the serotonin receptor signaling pathway was ranked second.7