Job stress and mental health among social workers: evidence from a field experiment at a public employment support institution in Japan

This study examines the causal effects of job stress on workers' mental health. Evaluating the causal relationship between job stress and workers' mental health is challenging due to an endogeneity problem, as heavy workloads and thus job stress are likely assigned to workers in good mental health condition. Endogeneity can also be problematic due to workers' unobserved heterogeneity, such as personal capacities and stress resistance, which are associated with both job stress and mental health outcomes. To solve this problem, we conduct a field experiment at a public employment support institution in Japan. In the experiment, we randomly assign counsellors to jobseekers who are visiting the institution for the first time. Since jobseekers experience varying levels of difficulty finding work, this random assignment results in unexpected workloads, adding job stress for counsellors. We then collect counsellors' daily records on mental health conditions for 4 consecutive weeks, matching the responses with the random assignment data on job counselling. Utilising a panel structure of the dataset and applying a fixed-effects model, we remove counsellors' time-invariant unobserved heterogeneities. We measure counsellors' mental health in terms of both subjective, self-reported perceptions and objective aspects of blood pressure and pulse. The results reveal that the job stress driven by newly assigned problematic jobseekers deteriorates aspects of counsellors' objective mental health, whereas it does not appear to affect their subjective mental health. This result suggests that workers can accumulate the negative effects of job stress on mental health that they may be unaware of.