Background: Major depressive disorder is a prevalent psychiatric illness characterized by mood disturbances and influenced by various environmental and genetic factors, yet its etiology remains largely unknown.
Methods: We profiled a self-reported depressive population in Japan with a focus on sociodemographic background, lifestyle, comorbidities, and genetic background, using data from two cohorts, a population-based cohort and a three-generation cohort, recruited by the Tohoku Medical Megabank Organization until December 2021.
Results: Our findings revealed that depression in the Japanese population is strongly associated with certain sociocultural features prevalent in Japan, such as social isolation, neuroticism, and introversion, as well as with well-known risk factors that include age and gender. Environmental factors related to the Great East Japan Earthquake, considered as cohort characteristics, were also strongly associated with the onset of depression. Moreover, using GWAS analysis of whole-genome sequencing data, we identified novel candidate genetic risk variants located on chromosomes 21 and 22 that are associated with depression in Japanese individuals; further validation of these risk variants is warranted.
Limitations: Our study has limitations, including uncertain clinical relevance resulting from the use of self-reported questionnaires for depression assessment. Additionally, the cohort exhibited a population bias, with greater representation of women than men.
Conclusions: Our results provide holistic insights into depression risk factors in Japanese adults, although their associations with depression are correlations. This supports the idea that targeted interventions and individualized approaches are important for addressing depression in the Japanese population.
Keywords: Cohort study; Demographics; Depression; Genetics; Japanese; Psychiatry.
Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.