Association of workplace social capital with psychological distress: results from a longitudinal multilevel analysis of the J-HOPE Study.

OBJECTIVES

Workplace social capital (WSC) is increasingly recognised as a social contextual determinant of workers' mental health, but longitudinal data are sparse. We aimed to evaluate the impact of changes in unit-level WSC on psychological distress among Japanese employees using a prospective multilevel repeated-measures design.

PARTICIPANTS AND STUDY DESIGN

We conducted a 2-year prospective cohort study with 1,944 men and 786 women aged 18-65 years. Participants worked at two manufacturing worksites in Japan and were free from mental illness from the first to third study waves. We used a three-level multilevel regression design to evaluate the prospective association of unit-level WSC with individual-level psychological distress. WSC was measured using a validated six-item instrument and individual-level psychological distress with the Kessler Psychological Distress Scale (K6).

RESULTS

The null model indicated a significant degree of between-work unit variation in psychological distress (intraclass correlation=0.1%, p<0.001). In the full model, each SD increase in unit-level WSC was associated with 0.69 point improvement in K6 scores (95% CI -1.12 to -0.26).

CONCLUSIONS

This prospective study builds on existing knowledge by showing an association between unit-level WSC and modest improvements in mental health among employees in Japan. We recommend that WSC is considered alongside other contextual influences when assessing employees' mental health risks.