title: Workplace social capital and the onset of major depressive episode among workers in Japan: a 3-year prospective cohort study.
abstract: This study examined the prospective association of workplace social capital (WSC) with major depressive episode (MDE) among Japanese employees.
  
  
  
  A 3-year prospective cohort study was conducted among 1058 employees from a private think-tank company who participated in a baseline survey; after excluding those with MDE in the past 12 months, 929 were followed up. WSC at baseline was measured using a 3-item scale. MDE was assessed at baseline and at follow-up every year, by using a web-based, self-administered version of the WHO Composite International Diagnostic Interview (WHO-CIDI) 3.0 depression section, based on the Diagnostic and Statistical Manual of Mental Disorders Fourth Edition: Text Revision (DSM-IV-TR)/DSM-5 criteria. Cox discrete-time hazards analyses were used to estimate HRs and 95% CIs, adjusting for covariates.
  
  
  
  A group with middle-level WSC scores had the lowest risk of MDE after being fully adjusted (HR 0.34, 95% CI 0.14 to 0.84, p=0.02). The relationship between WSC and MDE was U-shaped, although a non-linear model fit better than a linear model, with only marginally statistical significance (p=0.06). Dichotomised and continuous variables of WSC scores were significantly and negatively associated with MDE (p=0.03 and p<0.01, respectively).
  
  
  
  The current study replicated a previous finding from Finland that WSC was a protective factor of the onset of MDE in Japan. The slightly U-shaped relationship, that is, the group with high WSC having a small elevated risk of MDE, may reflect a dark side of WSC in a country with collectivity-oriented and hierarchy-oriented culture, such as Japan.
authors.affiliation: Department of Mental Health, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Asuka
authors.initials: A
authors.lastname: Sakuraya
authors.affiliation: Department of Mental Health, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Imamura
authors.affiliation: Department of Mental Health, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan, Kitakyushu, Japan.
authors.forename: Akiomi
authors.initials: A
authors.lastname: Inoue
authors.affiliation: Department of Public Health, Kitasato University School of Medicine, Sagamihara, Japan.
authors.forename: Akizumi
authors.initials: A
authors.lastname: Tsutsumi
authors.affiliation: Department of Mental Health, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Akihito
authors.initials: A
authors.lastname: Shimazu
authors.affiliation: Occupational Epidemiology Research Group, National Institute of Occupational Safety and Health, Japan, Kawasaki, Japan.
authors.forename: Masaya
authors.initials: M
authors.lastname: Takahashi
authors.affiliation: Department of Work Systems and Health, Institute ofIndustrial Ecological Sciences, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan, Kitakyushu, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Totsuzaki
authors.affiliation: Department of Mental Health, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Norito
authors.initials: N
authors.lastname: Kawakami
mesh_terms: D000328:Adult; D015331:Cohort Studies; D003865:Major Depressive Disorder / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D011446:Prospective Studies; D066270:Social Capital; D013315:Stress, Psychological / Q000453:epidemiology*; D000066477:Work Performance / Q000706:statistics & numerical data*; D017132:Workplace / Q000523:psychology* / Q000706:statistics & numerical data
keywords: Cohort studies; DEPRESSION; MENTAL HEALTH; SOCIAL CAPITAL; WORKPLACE