Longitudinal Study of the Psychological Impact of the July 2023 Akita Flooding: 3, 6, 9, and 12 Months After the Heavy Rain

Introduction: Natural disasters affect mental health negatively. Compared to earthquakes, climate change often affects the people of a region repeatedly, but there is limited data on the impact of repeated disasters on mental health. In 3, 6, 9, and 12 months after the heavy rain, we conducted a web survey on the mental health of victims of the heavy rain disaster in Akita Prefecture, Japan. Methods: To determine the psychological impact of the torrential rains in Akita Prefecture beginning in July 2023, the survey was administered 4 times: three months (October 13, 2023), six months (January 12, 2024), nine months (April 12, 2024), and one year (July 12, 2024) after the disaster. The municipalities where the participants lived were in the Akita Prefecture in Japan. Depression Anxiety Stress Scale (DASS) -21 and Impact of Event Scale Revised (IES-R) were used to evaluate psychological health. Results: There were significant differences in the scores for depression, anxiety, and stress, as indicated by the DASS-21, at four points: 3, 6, 9, and 12 months after the disaster, as determined by the Kruskal-Wallis tests (depression: p = 0.017; anxiety: p = 0.037; stress: p = 0.005). There were significant differences in the scores for PTSD as indicated by the IES-R between 6,1,2, 9, and 12 months after the disaster, as determined by the Kruskal-Wallis test (6 months and 12 months, p = 0.000; 9 months and 12 months, stress, p = 0.000). Conclusion: Heavy rain is unlike annual snowfall and low levels of sunshine, was found to have a significant impact on mental health immediately after the disaster. Akita Prefecture has a high suicide rate compared to the rest of Japan. In the event of a disaster in such an area, to provide rapid support is necessary to improve mental health.