Have restrictions on human mobility impacted suicide rates during the COVID-19 pandemic in Japan?

During the COVID-19 pandemic in Japan, various measures have been implemented to prevent the spread of infection, including restrictions on human mobility. A dynamic fluctuation in the number of suicides has been observed during this period. The question is whether the increase/decrease in suicides during the pandemic is related to changes in human mobility. To answer the same, we estimated incidence rate ratios (IRR) of suicide for changes in human mobility using the relative number of suicides by month from March 2020 to September 2021, based on the same months in 2019 as reference. The IRR of suicide during the pandemic were significantly lower in the months when mobility decreased—in both the previous and current month—than in the months when mobility was stable; the IRR of suicide were statistically higher in the months with increased mobility compared with the stable months. The burden from a decrease in one's mobility, which might lead to an increase in suicide, may not occur immediately, as seen in the delayed effects of unemployment. It may be important to investigate people's mental health and stress levels after pandemic restrictions were relaxed. The findings may help practitioners and families consider the timing of intervention.