Activities of the hypothalamo‐pituitary‐adrenal axis and autonomic nervous system following a strong earthquake

Abstract This study aimed to investigate the effects of post‐traumatic stress, caused by a strong earthquake, on the hypothalamo‐pituitary‐adrenal axis (HPA) and autonomous nervous system activity (ANS). Activities of the HPA (as salivary cortisol) and ANS (as heart‐rate variability [HRV]) were measured following the 2020 Elazig (Türkiye) earthquake (6.8 Richter Scale, classified as strong). A total of 227 participants (103 men (45%) and 124 women (%55)) provided saliva samples twice, namely, 1 week and 6 weeks after the earthquake. Of these participants, HRV was measured in 51 participants by 5 min continuous electrocardiogram (ECG) recording. Frequency‐ and time‐domain parameters of the HRV were calculated to assess the activity of ANS and low/high frequency (LF/HF) ratio was used as surrogate for sympathovagal balance. Salivary cortisol levels decreased from week 1 towards week 6 (17.40 ± 1.48 and 15.32 ± 1.37 ng/mL, respectively, p < 0.05). There were no gender differences (17.99 ± 2.63 and 16.90 ± 1.60 ng/mL, respectively for females and males, p > 0.05) for salivary cortisol levels. There were no differences in time‐ and frequency domain parameters of the HRV including LF/HF ratio (2.95 ± 0.38 ms 2 and 3.60 ± 0.70 ms 2 , respectively for week 1 and 6, p > 0.05). The data show that HPA axis activity, but not that of the ANS, remains higher 1 week after the earthquake but decreases afterwards towards the sixth week, suggesting that the HPA axis might be responsible for the long‐term effects of a traumatic event like a strong earthquake.