Structural Biases in the Japanese Diet-Depression Association

This commentary discusses potential structural biases in the study by Miyake et al., which reported an inverse association between adherence to a Japanese-style diet and depressive symptoms. Two key concerns are raised: unmeasured confounding by health consciousness, and limitations in the diet score's construction, which may reflect food quantity rather than dietary quality. These biases may impact the interpretation of the observed association and highlight the need for more refined methodological approaches in future research.