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The Physiology of Combat Stress Reaction

Combat stress reactions appear to result from exposure to a perceived imminent threat of serious personal injury or death to oneself or others in a combat or combat-related situation. If you are in a combat situation, you may experience extreme or overwhelming physiological reactions in your body. This CSR affects your ability to function during the event and might also be re-experienced after the event, sometimes for many years. Until recently, a CSR was thought to be temporary, situation-specific, and without long-term or impact beyond the battlefield. Recent evidence shows that CSRs may be associated with serious long-term effects, and with potential earlier mortality. You may be able to counter the negative impact of a CSR by recognizing the signs and symptoms of a CSR quickly. Quick CSR recognition will help you take better care of yourself and those you care about.

What a Combat Stress Reaction May Look Like

CSRs can be evident by physical and/or psychological signs or symptoms. CSRs can affect anybody and should be considered a red flag to seek help. For example, during an intense firefight in Afghanistan, a soldier became confused and disoriented, then began recklessly charging up and down the field between their unit and the enemy. A medic found the soldier's heart rate and blood pressure were dangerously high, so they were taken to an aid station. After some rest and reassurance, the soldier’s heart rate slowed, and they returned to their normal state. The soldier resumed duty the next day, after their sudden CSR appeared resolved.

CSRs are intense responses to extreme life-threatening combat stressors and are considered "normal" responses to abnormal events. CSRs may look different in different people. Symptoms can include a "power up" response with a dramatically increased heart rate, agitated behavior, intense anger or fear, and a single-minded focus on the threat (tunnel vision). Conversely, CSRs can involve a shutdown response with lower heart rate and blood pressure, frozen behavior, numb emotions, and detachment from surroundings and the mission. Other CSR effects can be loss of motor control, auditory trouble, irrational behavior, and inability to think clearly.

How the Human Body Responds to Life-threatening Combat Stressors

Most human body systems like to maintain a state of balance with bodily functions running optimally. Under typical, non-stressful conditions, our heart rate, hormones, oxygen level, and body temperature are perfectly balanced. Stressors, or stressful situations, may knock us out of balance, and extreme stress may knock us extremely out of balance. Heart rates during CSRs may jump to 200-300 beats per minute in less than one second (the average heart rate is 70 beats per minute)!

When you encounter a life-threatening situation in combat, your body's first instinct is survival. Our autonomic nervous system manages our body's response to stress and has two parts: the sympathetic nervous system — the arousal or "power up" system, and the parasympathetic nervous system — the shutdown or "power down" system. Under very stressful conditions, our bodies can naturally power up or power down to excess. If you are in a combat setting, these reactions can help you survive, fight, find cover, or escape. But it's possible for CSRs to become severe, which impair your operational performance, your ability to function, and the unit.

Where Do You Go from Here?

Even a single traumatic incident can follow a combatant into daily life. CSRs are hardwired survival responses triggered by the autonomic nervous system; the reactions are instant, automatic survival reactions to life-threatening situations. Understanding this biological process can help you recognize a CSR in yourself and in other service members. Someone can walk around feeling like or believing that there’s still a substantial threat of harm long after the threat of harm has passed; or at times may become agitated, panicky, or frozen but not know why. Anybody exposed to life-threatening combat stressors can experience a CSR and therefore it’s not a sign of weakness.

If you experienced a CSR while deployed and you have been re-experiencing the event in your imagination along with some of the physical signs or symptoms listed above, there might be a connection between these occurrences. You may also be at risk for having another CSR if you deploy again or participate in a combat-related field operation. A mental health provider can help you break the link between the past CSR and any current re-experiencing and may lower the risk of future CSRs. Seek help that teaches you how to change psychophysiology under high stress or unpredictability. Examples include learning emotion regulation, heart rate, and deep breathing techniques. For example, the Breathe2Relax app trains you on the “belly breathing” technique that has shown potential benefits for your overall mental health.

Talk to a Professional and Get Support

Specialized intervention to support military members with combat stress response is available. Reach out to a health care professional if you show signs of a CSR, need additional support, or for any other mental health support.


U.S. Emergency Services: 911

If you have an emergency or are in crisis, please contact the Military Crisis Line or the Suicide & Crisis Lifeline. Dial 988 and press 1 or text 838255.
Are you calling the Military/Veterans Crisis Line from overseas? The country code to reach the United States will be required for each of these numbers, depending on your location.

  • Europe, call: 844-702-5495 or DSN 988
  • Pacific, call: 844-702-5493 or DSN 988
  • Southwest Asia, call: 855-422-7719 or DSN 988


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Last Updated: April 09, 2024
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