Associations of the A118G OPRM1 polymorphism with sociotropy and interpersonal sensitivity

BACKGROUND: The μ‐opioid receptor (MOR) plays an important role in social bonding behaviors, while it is implicated in the pathophysiology of depression. It is shown that the A118G polymorphism (rs1799971) of the MOR gene (OPRM1) causes amino‐acid exchange from Asn to Asp, and that this polymorphism is associated with altered mu‐opioid receptor function. Meanwhile, sociotropy/autonomy and interpersonal sensitivity are personality vulnerabilities to depression characterized by distinctive interpersonal styles. The present study tested the hypothesis that the functional A118G OPRM1 polymorphism influences these personality traits. METHODS: The subjects were 402 physically and mentally healthy Japanese volunteers. Sociotropy and autonomy were measured by the Sociotropy‐Autonomy Scale, and interpersonal sensitivity was evaluated by the Interpersonal Sensitivity Measure. The A118G polymorphism of the OPRM1 was determined by the PCR method. RESULTS: In one factor analysis of covariance, there were differences in scores of sociotropy (uncorrected p < .001, corrected p < .003) and interpersonal sensitivity (uncorrected p = .015, corrected p = .045), but not autonomy, among the A/A, A/G, and G/G genotypes. Post hoc LSD tests showed that sociotropy scores were higher in the A/A group than in the A/G (p = .029) and G/G (p < .001) groups, and higher in the A/G group than in the G/G group (p = .004). Interpersonal sensitivity scores were higher in the A/A group than in the A/G (p = .023) and G/G (p = .009) groups. CONCLUSION: This study suggests that the A118G OPRM1 polymorphism is associated with sociotropy and interpersonal sensitivity, interpersonal vulnerabilities to depression.