# Stress and Heart Rate Variability: A Meta-Analysis and Review of the Literature [[Heart Rate Variability]] Hye-Geum Kim1, Eun-Jin Cheon2, Dai-Seg Bai3, Young Hwan Lee2*, and Bon-Hoon Koo1 1Department of Psychiatry, College of Medicine, Yeungnam University, Daegu, Republic of Korea 2Department of Pediatrics, College of Medicine, Yeungnam University, Daegu, Republic of Korea 3Division of Clinical Psychology, Department of Psychiatry, Yeungnam University Medical Center, Daegu, Republic of Korea - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5900369/ Paper - [[Stress and Heart Rate Variability- A Meta-Analysis and Review of the Literature.pdf]] # Summary - During chronic stress, the sympathetic nervous system is hyper activated causing physical, psychological, and behavioural abnormalities. - At present (2018), there is no universally recognised standard for stress evaluation. - HRV is the fluctuation of the length of heart beat intervals [[4](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5900369/#b4-pi-2017-08-17)]. HRV represents the ability of the heart to respond to a variety of physiological and environmental stimuli [[5](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5900369/#b5-pi-2017-08-17)]. Low HRV conveys a monotonously regular heart rate. Moreover, low HRV is associated with impaired regulatory and homeostatic autonomic nervous system (ANS) functions, which reduce the body’s ability to cope with internal and external stressors ## What's the automatic regulation of psychological stress conditions? - This is abit techinical. ## Theoretical significance of heart rate variability - their results showed that increases in stress were associated with decreases in the RR interval. Moreover, psychological stress was significantly associated with an increase in the LF/HF ratio, suggesting increased SNS activity during stressful periods of the day [[35](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5900369/#b35-pi-2017-08-17)] ### Clinical Applications of HRV - Because many factors influences HRV, "In clinical situations, HRV can be considered a tool that reflects heart activity and overall autonomic health, rather than specific mental illnesses or disease states. Thus, when evaluating the relationship between stress and HRV, it is essential to consider the overall autonomic context as well as the patient’s medical and psychological history." # Hans Seyle proposed a three-stage stress response model. - The first stage is the “alarm reaction stage,” in which the body reacts to a stressor with the fight-or-flight response and activates the SNS. - The second stage is the “resistance stage,” in which the body adapts to the stressor. During this stage, the PNS restores many physiological functions to normal, while the body focuses its resources against the stressor. Although the outward appearance of the organism seems normal, blood glucose, cortisol, and adrenalin levels remain elevated. - If a stressor continues beyond the body’s capacity to cope, the organism exhausts its resources, making it susceptible to disease or death. This “exhaustion stage” is reached when the acquired adaptation or resistance is lost.