When humans are confronted with potentially dangerous situations (either mentally or physically) a fight or flight reaction is triggered. This is also known as an acute stress response. Biologically this results in an increase in heart rate, blood pressure and breathing rate. This biologic response is mediated by the sympathetic branch of the nervous system. Once that threat is gone it takes between 20-60 minutes for the body to come back to normal. This response is mediated by the parasympathetic branch.
When flight or flight kicks in the HR increases. But that is not enough to tell if someone is stressed. To understand when someone is actually under stress we look at something called variability, in particular the variations between each heart beat.
HRV is sensitive to the changes in the autonomic nervous system (ANS). 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.
A study published in March 2018 in the Psychiatry Investigation Journal has studied the correlation between stress and heart rate variability.
” During chronic stress, the sympathetic nervous system is hyperactivated, causing physical, psychological, and behavioural abnormalities. At present, there is no accepted standard for stress evaluation. “
However, few studies have confirmed whether HRV is a good indicator of stress. This is what the study analyses in great detail. It looked at the most popular studies databases (WoS, PubMed and Google Scholar) at articles published from 2007 to 2017 that used HRV as an indicator for stress.
The study concluded that the current neurobiological evidence suggests that HRV is impacted by stress and supports its use for the objective assessment of psychological health and stress.
In view of observations of stress-associated variation in HRV and existing neurobiological evidence, HRV may be used as an objective assessment of stress and mental health.