[Association between mild physical injury and psychological distress: Shichigahama Health Promotion Project]

Objective Although a number of previous studies have investigated the association between natural disaster-related physical injury and mental health, very few have focused on mild physical injury. The aim of this study was to evaluate the association between natural disaster-related mild physical injury and psychological distress in a cross-sectional study.Method This study is a part of the Shichigahama Health Promotion Project, which was conducted in cooperation with the Tohoku University and Shichigahama Town, Miyagi Prefecture, after the Great East Japan Earthquake (GEJE). We conducted the research about one year after the GEJE, and performed logistic regression analyses using 3,844 participants (1,821 males/2,023 females) aged 20 years or older, who answered all the questions on physical injuries and the Kessler 6 scale (K6), after adjusting for gender, age, social factors, and lifestyles. Psychological distress was defined as a K6 score ≥ 13 out of 24 points. We also investigated the effect of other disaster situations on the association between mild physical injury and psychological distress by stratifying the dataset by bereavement, witnessing someone's death, and house damage.Results The participants with physical injury were at a significantly higher risk of psychological distress, with an adjusted odds ratio (aOR) of 2.05 and 95% confidence interval (CI) of 1.26-3.34, than those uninjured. Additionally, the participants with mild physical injury were at a significantly higher risk of psychological distress (aOR=2.18, 95% CI=1.32-3.59). In the subgroup of participants with small-scale house damage, mild physical injury was significantly associated with psychological distress with an aOR of 4.01 and 95% CI of 2.03-7.93, whereas not in the subgroup of those with large-scale house damage, and a significant interaction was detected between mild physical injury and house damage.Conclusion We investigated the association between natural disaster-related physical injury and psychological distress in a cohort of approximately 4,000 residents in an area devastated by the GEJE. In this study, natural disaster-related physical injury was positively associated with psychological distress. The finding indicates that even mild physical injury can be an indicator of high risk for psychological distress.