How does the impact of the COVID-19 state of emergency change? An analysis of preventive behaviors and mental health using panel data in Japan

This study applies the difference-in-difference method on panel data collected from internet surveys to investigate changes in the preventive behaviors and mental health of individuals as influenced by the COVID-19 state of emergency declaration between March and June 2020. The key findings are: (1) The declaration led people to exhibit preventive behaviors but also generated negative emotions; (2) Such behaviors persisted even after deregulation of the state of emergency; (3) Making the declaration early (vs. late) had a larger effect on preventive behavior, with the gap between residents’ behaviors for areas that made early vs. late declarations persisting after the deregulation; and (4) The effects on mental health diminished during the state of emergency and disappeared after its deregulation.