Sense of coherence modifies the effect of overtime work on mental health

In the occupational health field, it is important to know how workload influences mental health. Overtime work and job strain appear to affect the mental health status of workers. Sense of coherence (SOC) may mediate the relationship between work stress and mental health. Since SOC represents a personal ability to manage psychological stressors, we hypothesized that a strong SOC would modify the adverse effect of an objective measure of overtime work on mental health.

A total of 1,558 Japanese workers employed in an information technology company were asked to complete a 3-item SOC Questionnaire and 28-item General Health Questionnaire (GHQ) to assess mental health status. Workload was assessed by the actual amount of overtime work hours recorded by the company.

Multiple regression analysis revealed a main effect of overtime work (β=0.08, p=0.0003) and SOC scores (β=0.41, p <0.0001) on GHQ scores. There was a tendency toward interaction between overtime work and SOC scores (β=0.05, p=0.051). Simple slope analysis supported this association (-1 SD below the mean, simple slope=0.04, SE=0.01, p < 0.0001; +1 SD above the mean, simple slope=0.01, SE=0.01, p=0.188).

These results suggest that SOC buffers the mental health impacts of workload as measured by an objective index of overtime work, and should be considered when assessing the effects of workload on mental health.