Associations Between External Radiation Doses and the Risk of Psychological Distress or Post-traumatic Stress After the Fukushima Daiichi Nuclear Power Plant Accident: the Fukushima Health Management Survey

Background The relationship between radiation levels and mental health status after a nuclear disaster is unknown. We examined the association between individual external radiation doses and psychological distress or post-traumatic stress after the Fukushima Daiichi nuclear power plant accident in March 2011 in Japan. Methods The Mental Health and Lifestyle Survey was conducted from January 2012. Based on the estimated external radiation doses for the first 4 months, a total of 64,184 subjects were classified into <1 mSv, 1 to <2 mSv, and ≥2 mSv groups. Odds ratios (ORs) and 95% confidence intervals (CIs) of psychological distress and post-traumatic stress, with the <1 mSv group as the reference, were calculated using logistic regression analysis adjusted for age, sex, evacuation, perception of radiation risk, and subjective health status. Results The prevalence of psychological distress/post-traumatic stress in the <1 mSv, 1 to <2 mSv, and ≥2 mSv groups was 15.1%/22.1%, 14.0%/20.1%, and 15.0%/21.7%, respectively. In women, although the ≥2 mSv group tended to have a higher risk of psychological distress with the age-adjusted OR of 1.13 (95% CI, 0.99–1.30), the adjusted OR decreased to 1.00 (95% CI, 0.86–1.16) after controlling for all variables. On the other hand, there were no dose-dependent associations between radiation dose and post-traumatic stress. Conclusion Although external radiation doses were not associated with psychological distress, evacuation and perception of radiation risk may increase the risk of psychological distress in women in the higher dose group.