Seismic activity and development of mood disorders: Findings from the 2016 Kyungju earthquake

An earthquake with a moment magnitude of 5.8 occurred in Kyungju on 12 September 2016. Although the earthquake was the largest seismic activity in Korean history, there were no direct casualties from the event. This study evaluated whether a moderate-level earthquake is related to acute development of mood disorders in earthquake-exposed residents.

The healthcare information of residents (n = 865,263) living in Kyungju and control cities (Gimpo, Jeonju, Gimhae, and Pohang) over a 10-year period (from 2010 to 2019) was gathered from the national health insurance database. Difference-in-difference analysis was used to compare the daily incidence of mood disorders (manic episode; bipolar affective disorder; depressive episode; recurrent depressive disorder) 20 weeks before (reference: -20 to -11 weeks, period 1: -10 to -1 weeks) and after (period 2: 0-9 weeks, period 3: 10-19 weeks) the earthquake. Subregional analyses based on the distance to the epicenter and stratification analyses by sex, age, and income were conducted.

The weekly average incidence rate (/100,000 persons) of mood disorders in Kyungju residents increased from 27.0 (-20 to -11 weeks) and 28.3 (-10 to -1 weeks) persons before the earthquake, to 38.1 persons (0 to 9 weeks) after the earthquake. A significant increase in the risk of developing mood disorders was observed in Kyungju residents during the 0 to 9 weeks after the earthquake when compared to the control cities [relative risk (95 % confidence intervals): vs. Gimpo, 1.40 (1.05, 1.88); vs. Jeonju, 1.45 (1.14, 1.84); vs. Gimhae, 1.48 (1.14, 1.93)]. The increase was more prominent in women, low-income individuals, and those living closer to the epicenter.

Moderate-level earthquakes without direct casualties may cause mood disorders in residents living in affected areas. Mental health aid programs should be provided to earthquake victims even if the earthquake has caused limited life and property loss.