General adaptation syndrome (GAS) is the three-stage process that describes the physiological changes your body goes through when under stress.

Stress is a common occurrence. While you can’t remove every single stressor from your life, it’s possible to manage stress and maintain your health. This is important because stress can cause mental fatigue, irritability, and insomnia.

But even if you know the physical effects of stress, you may be unaware of the different stages of stress, known as general adaptation syndrome (GAS). When you understand the different stages of stress and how the body responds in these stages, it’s easier to identify signs of chronic stress in yourself.

Read more: 20 effects of stress on the body »

Hans Selye, a medical doctor and researcher, came up with the theory of GAS. During an experiment with lab rats at McGill University in Montreal, he observed a series of physiological changes in the rats after they were exposed to stressful events.

With additional research, Selye concluded that these changes were not an isolated case, but rather the typical response to stress. Selye identified these stages as alarm, resistance, and exhaustion. Understanding these different responses and how they relate to each other may help you cope with stress.

Read more: 10 simple ways to relieve stress »

1. Alarm reaction stage

The alarm reaction stage refers to the initial symptoms the body experiences when under stress. You may be familiar with the “fight-or-flight” response, which is a physiological response to stress. This natural reaction prepares you to either flee or protect yourself in dangerous situations. Your heart rate increases, your adrenal gland releases cortisol (a stress hormone), and you receive a boost of adrenaline, which increases energy. This fight-or-flight response occurs in the alarm reaction stage.

2. Resistance stage

After the initial shock of a stressful event and having a fight-or-flight response, the body begins to repair itself. It releases a lower amount of cortisol, and your heart rate and blood pressure begin to normalize. Although your body enters this recovery phase, it remains on high alert for a while. If you overcome stress and the situation is no longer an issue, your body continues to repair itself until your hormone levels, heart rate, and blood pressure reach a pre-stress state.

Some stressful situations continue for extended periods of time. If you don’t resolve the stress and your body remains on high alert, it eventually adapts and learns how to live with a higher stress level. In this stage, the body goes through changes that you’re unaware of in an attempt to cope with stress.

Your body continues to secrete the stress hormone and your blood pressure remains elevated. You may think you’re managing stress well, but your body’s physical response tells a different story. If the resistance stage continues for too long of a period without pauses to offset the effects of stress, this can lead to the exhaustion stage.

Signs of the resistance stage include:

  • irritability
  • frustration
  • poor concentration

3. Exhaustion stage

This stage is the result of prolonged or chronic stress. Struggling with stress for long periods can drain your physical, emotional, and mental resources to the point where your body no longer has strength to fight stress. You may give up or feel your situation is hopeless. Signs of exhaustion include:

  • fatigue
  • burnout
  • depression
  • anxiety
  • decreased stress tolerance

The physical effects of this stage also weaken your immune system and put you at risk for stress-related illnesses.

GAS can occur with any type of stress. Stressful events can include:

  • a job loss
  • medical problems
  • financial troubles
  • family breakdown
  • trauma

But while stress is unpleasant, the upside is that GAS improves how your body responds to stressors, particularly in the alarm stage.

The fight-or-flight response that occurs in the alarm stage is for your protection. A higher hormone level during this stage benefits you. It gives you more energy and improves your concentration so you can focus and tackle the situation. When stress is short-term or short-lived, the alarm stage isn’t harmful.

This isn’t the case with prolonged stress. The longer you deal with stress, the more harmful it is to your health. You also don’t want to remain in the resistance stage for too long and risk entering the exhaustion stage. Once you’re in the exhaustion stage, prolonged stress raises the risk for chronic high blood pressure, stroke, heart disease, and depression. You also have a higher risk for infections and cancer due to a weaker immune system.

Since it’s not possible to eliminate every stressor, it’s important to find ways to cope with stress. Knowing the signs and stages of stress can help you take appropriate steps to manage your stress level and lower your risk of complications.

It’s essential for your body to repair and recover during the resistance stage. If not, your risk for exhaustion rises. If you can’t eliminate a stressful event, regular exercise can help you cope and maintain a healthy stress level. Other techniques for stress management include meditation and deep-breathing exercises.