General Adaptation Syndrome (GAS):

General adaptation syndrome (GAS) is a theory of fight-or-flight response (FFR), describing it’s three stress-induced, physiological changes—how it behaves faced with a stressor (alarm stage) and faced with prolonged stress (resistance and exhaustion stages) when the body systems start to break down. It also explains why untreated anxiety disorders can lead to psychologically and physiologically worsened conditions.