Association between job stress and depression among Japanese employees threatened by job loss in a comparison between two complementary job-stress models

OBJECTIVES: This study compared the separate effects produced by two complementary stress models--the job demand-control model and the effort-reward imbalance model--on depression among employees threatened by job loss. METHODS: A cross-sectional analysis was conducted to examine these associations among 190 male and female employees who responded to a self-administered questionnaire in a small Japanese plant with economic hardship. The employees were engaged in 2 job types--direct assembly line and indirect supportive tasks--and the latter was threatened by job loss because of downsizing. Independent variables were measured by the Japanese versions of Karasek's demand-control questionnaire and Siegrist's effort-reward imbalance questionnaire. Depression was assessed by the Center for Epidemiologic Studies Depression Scale. RESULTS: The employees with indirect supportive tasks (target for downsizing) were more likely to have depressive symptoms than direct assembly-line workers. Job strain, a combination of high demand and low control at work, was more frequent among the latter, while the combination of high effort and low reward was more frequent among the former. After adjustment for work environment factors, low control odds ratio (OR) 4.7, effort reward imbalance (OR 4.1), and overcommitment (the person characteristic included in the effort-reward imbalance model) (OR 2.6) were independently related to depression. There is some indication that these effects were particularly strong in the subgroup suffering from potential job loss. CONCLUSIONS: This study confirms that the 2 job stress models identify different aspects of stressful job conditions. Moreover, effort-reward imbalance and low control at work are both associated with symptoms of depression.