What Is General Adaptation Syndrome (GAS)?

The stages the body goes through in response to stress

Everyone has experienced stress—both negative and positive. Enduring stress has physical and mental effects on the body.

General adaptation syndrome (GAS) is a term that describes the physiological changes the body automatically goes through when it responds to stress. First developed by Hans Selye in 1936, GAS is considered to be a pioneering modern biological formulation of stress.1

GAS has three stages: alarm, resistance, and exhaustion. The more stages your body goes through, the greater the risk of long-lasting negative effects. Prolonged stress can impact your physical and mental health.

Understanding GAS, including how it is triggered, can help you reduce your stress.

Anxious mixed race woman paying bills on laptop.
Jose Luis Pelaez Inc. / Getty Images


Hans Selye's research in the 1950s defined the three stages of GAS: the Alarm Reaction, the Stage of Resistance, and the Stage of Exhaustion.2


The alarm reaction stage is the body’s initial response to stress. This stage is also referred to as the fight-or-flight response. During this stage, the body's sympathetic nervous system is activated by the sudden release of hormones.

The sympathetic nervous system is a part of the autonomic nervous system, which regulates the functions of your heart, stomach, bladder, and intestines, as well as your muscles. You are not aware that this system is working because it automatically responds to stimuli.

When the sympathetic nervous system is activated, it stimulates the adrenal glands. The glands, in turn, trigger the release of certain hormones, including adrenaline and noradrenaline.

The hormone release causes physical symptoms, such as an increase in heart rate and breathing rate, as well as a rise in blood pressure.3

Physical signs of being in the alarm response stage include:

  • Dilated pupils
  • Increased heart rate
  • Rapid breathing
  • Trembling
  • Pale or flushed skin
  • Heightened senses

According to Selye, most of the symptoms of the alarm response stage disappear or are reversed in the next stage (resistance), then reappear in the final stage of exhaustion.2


The resistance stage is when your body tries to repair itself after the initial shock of stress. If the stressful situation is no longer present and you can overcome the stress, your heart and blood pressure will start to return to prestress levels during this stage.

However, if the stressful situation continues for a long time or if you do not resolve the stress, your body will never receive a clear signal to return to normal functioning levels. This means it will continue to secrete the stress hormones and your blood pressure will stay high.

Prolonged levels of high stress can cause disturbances in the immune, digestive, cardiovascular, sleep, and reproductive systems. You might have symptoms such as:

  • Bowel issues
  • Headaches
  • Sleeplessness
  • Sadness
  • Frustration
  • Irritability
  • Poor concentration

Prolonged stress that is not resolved leads to the third stage (exhaustion).


Prolonged or chronic stress leads to the last stage of exhaustion. Enduring stressors without relief drains your physical, emotional, and mental resources to the point where your body is no longer able to cope with stress.

Signs that you are in the exhaustion stage include:

  • Fatigue
  • Burnout
  • Decreased stress tolerance

The physical effects of prolonged stress can weaken your immune system and increase your risk of heart disease, high blood pressure, diabetes, and other chronic health conditions, including mental health disorders such as depression or anxiety.4


Selye developed GAS after studying how the human body reacted to physical stressors, such as being exposed to cold temperatures or physical overexertion.

It is now understood that many situations, including those that cause psychological rather than physical stress, can cause GAS.5

Examples of stressors that can trigger GAS include:

  • Daily stress (such as pressure at school, work, or at home relating to your family)
  • A sudden change in your life (such as losing a job, divorce, or illness)
  • Traumatic experiences (such as abuse, a major accident, and war)

Positive Stress

GAS is not only triggered by stressors that cause distress; it can also be triggered by situations in which the stressor is considered positive, or pleasant (known as eustress).6

For example, some people see the stress of an upcoming exam as a positive because it helps them to stay motivated. Others might enjoy the fear they feel while watching a scary movie.

All of us have different stressors. What seems like a threat to one person might be perceived as a positive challenge to someone else.

GAS and Medical Conditions

GAS is not a medical condition that you can be diagnosed with; rather, it's the process your body goes through automatically when it experiences stress.

However, if you are experiencing chronic stress that is negatively affecting your life, it's important that you get help. Mental health conditions that have symptoms related to experiencing stress over extended periods include:


Stress mitigation techniques can help you cope with GAS.7 Examples you might want to explore include:

Anyone can become overwhelmed by stress. If you or a loved one are struggling, contact the Substance Abuse and Mental Health Services Administration (SAMHSA) National Helpline at 800-662-4357 for information on support and treatment facilities in your area. For more mental health resources, see our National Helpline Database.


General adaptation syndrome (GAS) describes the process your body goes through when you are exposed to any kind of stress, positive or negative. It has three stages: alarm, resistance, and exhaustion.

If you do not resolve the stress that has triggered GAS, it can lead to physical and mental health problems.

A Word From Verywell

The physical changes your body goes through in response to stress are not harmful on their own. However, when stress continues for a long time and your body enters the exhaustion stage, it can cause long-term problems.

Understanding which stressors affect you and learning strategies to cope with stress can help you avoid the consequences of chronic stress. If you are having a hard time coping with stress, it's important to reach out to your doctor or a mental health professional for support.

Frequently Asked Questions

What is general adaptation syndrome?

General adaptation syndrome (GAS) is the pattern of physical changes the body goes through after being exposed to stress. It is not a medical diagnosis; rather, it is a process the body goes through in response to stress.

What are the three stages of general adaptation syndrome?

There are three stages of GAS: alarm, resistance, and exhaustion.

Who discovered general adaptation syndrome?

Hans Selye developed GAS in 1936. It is considered a pioneering modern biological formulation of stress.1

What triggers general adaptation syndrome?

Any kind of stressor—both unpleasant and rewarding—can trigger general adaptation syndrome.