Further haplotype-based association analysis showed a significant association of the haplotype C-D derived from two markers at the core promoter region with schizophrenia (rs2230178 and rs6145976, p = 0.01), and reporter gene activity assays showed that the haplotype C-D-C-C derived from rs2230178-rs6145976- rs2017365-rs739669 had significant lower promoter activity than that of the C-I-T-T, suggesting that C-D haplotype that is associated with schizophrenia may have reduced expression of the DLG4 gene in patients with schizophrenia. This evidence concerns the gene DLG4 and schizophrenia.