Open Access Research article

Folate intake and depressive symptoms in Japanese workers considering SES and job stress factors: J-HOPE study

Koichi Miyaki1*, Yixuan Song1, Nay Chi Htun12, Akizumi Tsutsumi3, Hideki Hashimoto4, Norito Kawakami5, Masaya Takahashi6, Akihito Shimazu5, Akiomi Inoue7, Sumiko Kurioka8 and Takuro Shimbo1

Author Affiliations

1 Division of Clinical Epidemiology, Department of Clinical Research and Informatics, National Center for Global Health and Medicine, Toyama 1-21-1, Shinjuku-ku, Tokyo, Japan

2 Department of Molecular Epidemiology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan

3 Department of public Health, Kitasato University School of Medecine, Sagamihara, Kanagawa, Japan

4 Department of Health Economics and Epidemiology Research, School of Public Health, University of Tokyo, Tokyo, Japan

5 Department of Mental Health, Tokyo University Graduate School of Medicine, Tokyo, Japan

6 National Institute of Occupational Safety and Health, Kawasaki, Kanagawa, Japan

7 Department of Mental Health, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Kitakyushu, Fukuoka, Japan

8 Occupational Health Training Center, University of Occupational and Environmental Health, Kitakyushu, Fukuoka, Japan

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BMC Psychiatry 2012, 12:33  doi:10.1186/1471-244X-12-33

Published: 20 April 2012



Recently socioeconomic status (SES) and job stress index received more attention to affect mental health. Folate intake has been implicated to have negative association with depression. However, few studies were published for the evidence association together with the consideration of SES and job stress factors. The current study is a part of the Japanese study of Health, Occupation and Psychosocial factors related Equity (J-HOPE study) that focused on the association of social stratification and health and our objective was to clarify the association between folate intake and depressive symptoms in Japanese general workers.


Subjects were 2266 workers in a Japanese nationwide company. SES and job stress factors were assessed by self-administered questionnaire. Folate intake was estimated by a validated, brief, self-administered diet history questionnaire. Depressive symptoms were measured by Kessler’s K6 questionnaire. “Individuals with depressive symptoms” was defined as K6≧9 (in K6 score of 0–24 scoring system). Multiple logistic regression and linear regression model were used to evaluate the association between folate and depressive symptoms.


Several SES factors (proportion of management positions, years of continuous employment, and annual household income) and folate intake were found to be significantly lower in the subjects with depressive symptom (SES factors: p < 0.001; folate intake: P = 0.001). There was an inverse, independent linear association between K6 score and folate intake after adjusting for age, sex, job stress scores (job strains, worksite supports), and SES factors (p = 0.010). The impact of folate intake on the prevalence of depressive symptom by a multiple logistic model was (ORs[95% CI]: 0.813 [0.664-0.994]; P =0.044).


Our cross-sectional study suggested an inverse, independent relation of energy-adjusted folate intake with depression score and prevalence of depressive symptoms in Japanese workers, together with the consideration of SES and job stress factors.