Heart Rate Variability (HRV) is variation in time intervals between heartbeats, often measured in milliseconds.HRV reflects the interplay between sympathetic and parasympathetic branches of ANS. The variation between heartbeat is low in sympathetic activation and high in parasympathetic mode.

While heart rate provides a basic measure of overall cardiac activity, HRV offers deeper insights into the body’s ability to adapt and respond to internal and external stressors. Altered HRV patterns, such as reduced variability, have been consistently linked to various mental health conditions, including anxiety disorders, depression, and PTSD.