Rationale: In clinical practice, ketamine, an antagonist of the N-methyl-D-aspartate receptor (NMDAR), is used to alleviate depressive symptoms in patients with major depressive disorder (MDD), especially in those with treatment-resistant depression (TRD). Accordingly, the human gene coding for the 2B subunit of the NMDAR (GRIN2B) is considered a promising candidate gene for MDD susceptibility.
Objectives: The primary aim of this study is to examine whether potentially functional polymorphisms of GRIN2B confer risk for MDD, and second to investigate whether GRIN2B acts as a genetic predictor for TRD in MDD patients.
Methods: We enrolled 178 TRD and 612 non-TRD patients as well as 779 healthy controls.
Results: Four potentially functional polymorphisms (rs1805502, rs890, rs1806201, and rs7301328) within GRIN2B were genotyped in all participants. The haplotype analysis found significant differences in the distribution of the G-T haplotype between the TRD and control groups (corrected P = 0.007), and the frequency of the G-T haplotype in TRD group was significantly higher than that in the controls (TRD/control ratio 0.31:0.21). Statistically significant differences in allele and genotype frequencies were detected between TRD and non-TRD groups for the rs1805502 polymorphism within GRIN2B. There was a significant allelic association between rs1805502 and TRD with an excess of the G allele in the TRD group, compared to non-TRD group (OR = 1.55, 95 % CI = 1.18-2.05, corrected P = 0.008).
Conclusions: These initial findings strengthen the hypothesis that GRIN2B not only confers susceptibility to TRD, but also plays a genetic predictor for TRD in MDD patients.