Post-disaster Changes in Social Capital and Mental Health: A Natural Experiment from the 2016 Kumamoto Earthquake.

Levels of social capital can change after a natural disaster; thus far, no study has examined how changes in social capital affect the mental health of disaster victims. This study examined how pre-disaster social capital and its changes after a disaster were associated with the onset of mental disorders. In October 2013, we mailed a questionnaire to participants of the Japan Gerontological Evaluation Study living in Mifune town (Kumamoto, Japan) and measured pre-disaster social capital. In April 2016, the Kumamoto earthquake struck the region. Three years after the baseline survey, post-disaster social capital and symptoms of mental disorders were measured using the Screening Questionnaire for Disaster Mental Health (SQD) (n = 828). A multiple Poisson regression indicated that a standard deviation of 1 in pre-disaster social cohesion at community-level reduced the risk of depression (relative risk [RR] = 0.44); a decline in social capital after the disaster elevated the risk among women (RR = 2.44). In contrast to social cohesion, high levels of social participation at community-level were positively associated with the risk of depression among women. Policymakers should pay attention to gender differences and the types of social capital when leveraging social capital for recovery from disasters.