Background: The pathophysiology of bipolar 1 disorder (B1D), a major psychiatric disorder with inflammatory origins and structural changes in the brain, is of great interest to researchers. Pro-inflammatory biomarkers and specific gene expression play pivotal roles in B1D development, and IFN-γ has emerged as an important inflammatory marker. The aim of this research was to determine whether the INF-γ +874 T/A polymorphism is associated with B1D susceptibility in an ethnic Iranian population.

Methods: The IFN-γ +874 T/A (rs2430561) gene polymorphism was studied in 106 B1D patients and 109 control subjects using sequence specific primers (SSPs) and amplification refractory mutation system-polymerase chain reaction (ARMS-PCR).

Results: Significant statistical differences in IFN-γ +874 T/A polymorphism genotype distribution were found between the patients and control subjects (P = 0.0006). Decreased risk of B1D was detected in the codominant model (T/T vs T/A and A/A, OR = 0.19, 95% CI = 0.07-0.49 for T/A, OR = 0.38, 95% CI = 0.12-1.24 for A/A, P value=0.0006), and in the dominant model (T/T vs T/A-A/A, OR = 0.21, 95% CI = 0.08-0.54, P = 0.0005). However, no significant difference in the IFN-γ polymorphism allele distribution was found between the two groups (P = 0.25).

Conclusions: The IFN-γ +874 T/A polymorphism may have a significant role in BID development.