-G308A tumor necrosis factor alpha functional polymorphism and schizophrenia risk: meta-analysis plus association study.

Research on -G308A functional polymorphism in the tumor necrosis factor alpha (TNFalpha) gene as a susceptibility factor for schizophrenia has provided contrasting results in different populations. Therefore we conducted a meta-analysis of the published case-control association studies and a replication study in a large sample. Meta-analyses (total sample: 2512 cases versus 3223 controls) showed that the AA genotype was weakly associated with schizophrenia susceptibility in Caucasoids (Odd Ratio OR=1.65, 95% CI=1.00-2.71 Z=1.98 p=0.05). The replication case-control association study (323 DSM-IV-TR schizophrenia patients and 346 controls) showed that the A allele conferred an increased susceptibility for schizophrenia only in males (OR=1.73, 95% CI=1.07-2.79, p=0.025), and the association became more specific when only patients of the paranoid subtype were compared to the controls (relative risk ratio=3.09, 95% CI=1.28-7.47, p=0.012). The presence of the A allele was also associated with a later age at onset of schizophrenia in the whole sample (F(1,291)=7.094, p=0.008). Our results confirm that TNFalpha A allele could have an effect on vulnerability to schizophrenia but further studies revaluating the role of gender and diagnostic subtypes are necessary to confirm these findings.