Stress or survival: what is the fight or flight response?

You just submitted a proposal at work and thought it went well. But your boss calls you into their office and tells you about a big mistake you missed. While you’re sitting across from them, you feel your blood pumping, your heart beating fast, and a cold sweat starting.

You feel the urge to get up and run away from the problem.

Everyone feels this kind of panic sometimes, whether it’s from work, a personal issue, or physical danger. When humans meet a threat of physical or psychological harm, our brains can activate an overwhelming response, known as the fight or flight response.

In many situations, this sudden fear is a useful motivator. But it can also become too much, especially if it’s consistent.

If you constantly experience a strong physiological reaction to stress, it's worth asking yourself: what’s the fight or flight response? Once you identify where your stress comes from, you can start down the path to managing it.

What is the fight or flight response?

Walter Bradford Cannon coined fight or flight response in the 1900s to refer to the physiological stress response. “Fight or flight” has now become a common phrase, but the response also includes “freezing”: being debilitated by fear and unable to act. 

The flight or flight (or freeze) response is a physiological response to danger. When you encounter a threat, your body activates the sympathetic nervous system, which helps you react quickly when your safety is at sudden risk.

For instance: run away, fight the danger, or freeze in fear. Human ancestors developed it to respond to physical dangers, like a natural disaster, a dangerous animal, or a falling tree branch. 

While modern life looks a lot different than the life of a hunter-gatherer, the fight or flight response is deeply embedded in human physiology, which is why it prevails today.

Even though we now have different stressors, like modern physical dangers and emotional triggers, we still experience physiological response.

You may more readily associate a fight or flight response with environmental triggers. This happens when you’re suddenly surprised or confronted by an imminent physical danger, which can be either a real or perceived threat. Environmental fight or flight response examples include:

• Slamming on the brakes to avoid a car accident

• Getting spooked by a strange noise in the middle of the night

• Jumping out of the way of oncoming motorists or bicyclists

• Reacting to an aggressive animal

• Being alert while walking alone in the dark

• Feeling discomfort around a stranger

• Being startled by someone who sneaks up on you

But dangers don’t have to be physical. Modern life is filled with obligations, pressures, and responsibilities that can create psychological or mental stress. These are emotionally charged but non-life-threatening situations that trigger the same fight-or flight response. Examples include:

• Having to give a speech in front of a large audience

• Feeling nervous about an important event, like a wedding

• Experiencing physical or social discomfort around new people

• Being on high alert due to a phobia, like a fear of heights

• Forgetting an important task

• Interacting with someone you feel strongly about, whether positive or negative

What happens to the body during the fight or flight response?

Everyone knows the feeling of that knot in the pit of your stomach in the face of stressful or dangerous situations. This physical sensation represents a complex interplay between the brain and the body to let you know it’s time to flee, fight, or freeze.

Let’s examine what the body is going through during the fight or flight response.

What’s the fight or flight response controlled by?

The fight or flight response initiates in the amygdala, also known as the primitive brain, which dictates how you emotionally and physically react to stimuli.

In moments of stress, the amygdala sends messages to the hypothalamus, activating your autonomic nervous system — heart rate, blood pressure, and respiration.

The autonomic nervous system (ANS) has two systems:

• The parasympathetic nervous system (PNS), which controls your freeze response

• The sympathetic nervous system (SNS), which controls your fight or flight response

What’s involved in the fight or flight response?

According to the National Center for Biotechnology Information’s report on physiological stress reaction, when danger stimulates your ANS, your body experiences several physiological changes. Immediately, your adrenal glands release adrenaline and cortisol, the body’s stress hormone.

The extra adrenaline raises your heart rate and blood pressure, which fills you with energy to face the danger. Meanwhile, extra cortisol performs several important functions:

• Pumps glucose into your blood vessels, which increases your blood pressure and fills you with energy.

• Tells your brain to use glucose more effectively by increasing the chemicals that repair damaged tissues.

• Shuts off non-essential or harmful bodily functions, like signaling your immune system to stay alert and others like the digestive system, reproductive system, and growth to rest.

The release of adrenaline and cortisol also stimulates different internal and external reactions, which vary from one individual to the next. These include:

• Heart rate: If you fight or flee, your increased heart rate will pump blood through your body, sending oxygen to major muscles. If you freeze, your heartbeat will decrease, making your muscles tighten and tense.

• Breathing: Your breathing will accelerate if you fight or flee to put more oxygen in the bloodstream — although if you breathe too quickly, you may hyperventilate. If you freeze, your respiration rate may actually decrease, or you might hold your breath.

• Skin: During this response, your hair might stand on edge (which is getting goosebumps) and your sweat glands will activate. All the blood pumping throughout the body could mean that some parts of your body flush while others turn pale.

• Hearing: Your hearing sharpens to take in the environment around you and sense more danger.

• Pain: The adrenaline pumping through your body doesn’t eliminate pain, but it will distract or delay your pain perception.

• Sight: Pupil dilation brings more light in and improves your overall sight and peripheral vision.

• Circulation: Cortisol increases blood flow to your major muscles, which could result in cold hands or feet.

Fight or flight response and anxiety

Physical symptoms of anxiety can be severe — like rapid breathing, muscle tension, and high blood pressure — and they’re often a direct result of the fight or flight response. When a situation makes you anxious, you might want to run away or feel frozen in place and unable to move. 

Anxiety-related fear results from two possible phenomena: an intolerance of uncertainty and anxiety sensitivity. Here’s an explanation of both:

• Intolerance of uncertainty: This is a cognitive, emotional, or behavioral reaction to your negative perception of an uncertain situation or outcome. For example, doing a presentation and not knowing how it went can make you feel anxious.

  You might feel the urge to leave the room or avoid the situation entirely for fear of a bad outcome.

• Anxiety sensitivity: Some people have a fear of anxiety symptoms themselves and their potential physical, mental, or social consequences. For example, worrying that you’re feeling nauseous due to anxiety can make the feeling worse.

  During the presentation, you may start to overthink your performance, talk too fast, or skip over important details.

Some people may be more prone to a fight or flight response, depending on their past experiences or mental health history. For example, people who frequently experience dangerous situations, like firefighters, are far more likely to activate instead of freeze when under immediate threat.

Likewise, people with PTSD often have less control over their acute stress responses. Their fear may be heightened in situations others don’t perceive as life-threatening, like the sound of a car backfiring or a darkly lit hallway.

Why try to manage the fight or flight response?

The fight-or-flight response manipulates normal physiological functions, and experiencing it often is tough on the body. It originally evolved to protect you when your life is at risk — not in moments of everyday stress.

Without properly treating chronic stress, you’re at risk of developing the following short and long-term issues:

• Cardiovascular disease, heart attack, and stroke

• Decreased white blood cells and a higher risk of disease

• Depression

• Loss of appetite

• Mental fatigue

• Low libido

• High blood pressure

• High cholesterol and triglyceride levels

• Unhealthy appetite

• Poor digestion

• Panic attacks

• Poor sleep patterns

4 tips for coping with fight or flight response

Depending on the root of your chronic stress activation, there are many ways to mitigate it. Anxiety-induced fight or flight response can be exhausting and prevent you from living your life. Here are a few ways to overcome fear and anxiety:

1. Emotional regulation

Controlling emotions looks different for everybody, but anyone can learn emotional regulation skills and figure out what works for them. Rather than suppressing your anxiety, emotional regulation teaches you to give it space, reflect on it, and accept it.

This method helps give you a choice to rewire your brain’s response and work through emotions instead of avoiding them.

2. Breathing techniques

Breathwork hacks into the ANS and stimulates the PNS, helping return you to a restful state. Breathing techniques can help trigger your PNS and eventually calm down. Regular practice reduces stress, boosts your immune system, and stimulates self-compassion.

3. Exercise

While anxiety may decrease your motivation to exercise, physical activity pumps your body with feel-good endorphins that put you in a better mood and decrease stress over time. Try 30 minutes of daily exercise to see the mental health benefits.

There are many options — try joining a local yoga class, doing an aerobics workout at home, or joining the gym and hiring a personal trainer. 

4. Therapy

You don’t have to manage your emotions on your own. If you’re having a difficult time developing self-awareness and overcoming anxiety, trying therapy can help.

Emotion Regulation Therapy, for example, focuses on understanding your triggers and developing personalized techniques to regulate stress.

Fight, flight, or relax

The fight or flight response evolved for a reason. We can’t avoid it, and we shouldn’t — it can be the difference between danger and safety. But learning the difference between what the fight or flight response is and what’s just stress is important to keeping your body and mind at rest when they need to be.

Once you develop a better understanding of your fight or flight response, you’re one step closer to bringing your stress levels down and regulating your emotions.