Abstract
PURPOSE: It is suggested that increased methylation of the brain-derived neurotrophic factor (BDNF) gene is involved in the pathogenesis of depression, while sociotropy and autonomy are proposed as personality vulnerability factors in cognitive model of depression. We examined the interrelation between BDNF gene methylation and sociotropy or autonomy, with taking into account the previously reported deleterious effect of parental overprotection on sociotropy. MATERIALS AND METHODS: The participants consisted of 90 healthy Japanese volunteers. Methylation levels of the BDNF gene in peripheral blood were quantified by bisulfite pyrosequencing. Sociotropy and autonomy were assessed by the Sociotropy-Autonomy Scale, and perceived parental protection was evaluated by the Parental Bonding Instrument. RESULTS: In Pearson's correlation analysis, there was a positive correlation between methylation levels of the BDNF gene and sociotropy scores (p<0.05) but not autonomy scores, and a positive correlation between maternal protection scores and sociotropy scores (p<0.05). In structural equation modeling, two models were proposed; the first one is that hypermethylation of the BDNF gene and maternal overprotection independently contribute to high sociotropy, and the second one is that maternal overprotection contributes to high sociotropy which then leads to hypermethylation of the BDNF gene. CONCLUSION: The present study suggests an interrelation between increased BDNF gene methylation and high sociotropy.