After the high magnitude earthquake and the subsequent tsunami in Japan on March 11, 2011, the residents of Fukushima Prefecture suffered not only from tremendous physical injury caused by the earthquake and tsunami but also from the effects of radiation contamination after a hydrogen explosion at the Fukushima Daiichi nuclear power plant on March 12, 2011. The complex Fukushima disaster is characterized by additional stress due to the fear of continued exposure to invisible radiation. We investigated whether there were any changes in the clinical mental state of patients in the inpatient ward of Fukushima Medical University Hospital, Japan, 7 days after the earthquake. There was no obvious change in the condition of two-thirds of the patients. Whereas one-third of patients had any change in their condition, several cases showed dramatic symptomatic improvement after the earthquake. Anxiety levels in the patients who originally showed coexisting anxiety disorders became exaggerated. The depressive state was improved after the earthquake in one patient with depression. One patient with restrictive-type anorexia nervosa resumed food consumption. These findings suggest that caregivers should be attentive to any symptomatic changes among patients with psychiatric disorders after sudden disasters.