Widening social inequity is a key concern for modern society, and is associated with psychiatric diseases including depression. Previous cohort-based studies have indicated a strong link between inequity and depression, where economic and material disadvantage are found important in explaining depressive symptoms. However, little is known about the underlying neural mechanism, mainly due to individual differences. To address this issue, we conducted a model-based (inequity-specific) multivariate voxel pattern analysis of functional magnetic resonance imaging (fMRI) during an economic game and tried to predict a long-term (one-year) changes in depression tendency. In our experiment, we first measured depression tendency (BDI-II), social value orientation (an established individual differences towards inequity during resource allocation), and fMRI during an ultimatum game from participants. Then, depression tendency was measured again one-year later from the same participants (n=73). We found that different social value orientations (i.e., prosocials and individualists) are associated with different distributions of the depression tendency (first BDI-II test), as well as dissociable fMRI activity in the amygdala and hippocampus in correlation with inequity. Most importantly, our multivariate analysis showed not only that fMRI voxel patterns in the amygdala and hippocampus induced by inequity can predict long-term (one-year) changes in depression tendency, but also that the amygdala and hippocampus contributed to an increase and decrease of depression tendency, respectively. These findings suggest that the amygdala and hippocampus play key roles in bridging inequity and depression.

研究助成：Research funds : PRESTO from JST, CREST from JST and by KAKENHI (22300139)