Generally curious..
In: Biology
Stress *is* physical.
Oh sure it can have a psychological cause, and colloquially those might be what the word is used for, but what it actually is is a heightened state of activation of the sympathetic nervous system, the body’s fight or flight response.
High blood pressure is an intended feature of the sympathetic nervous system. It helps get blood to your muscles if you’re trying to outrun a lion.
Maintaining high blood pressure for months or years in a row isn’t great for your heart.
All the blood vessels going to your digestive system get partially shut off since really if you’re running away from a lion you don’t have time to worry about digestion right now. Do *that* for too long and your stomach lining might not be able to rebuild itself as fast as your stomach acid is dissolving it.
When you experience stress, your body will respond by preparing for danger, it is designed to do so. It is a great system for when you think a lion may be near.
Increased cortisol heigtens your alertness, adrenaline increases heartrate. You are ready for fight or flight. You’re basically a racecar in the red. Like racecars, your body is not designed to be in the red all the time. Stuff starts breaking down after a while.
First of all, I know what you mean, but it’s still worth saying: psychological things are still physical since our brain is a physical organ. The fact that something is psychological does not make it any less physical or biological than something in our body.
There are a lot of scientific ideas about how exactly stress works, but the main and most popular one is that stress increases activity in something called the HPA axis (https://en.m.wikipedia.org/wiki/Hypothalamic-pituitary-adrenal_axis). This is just a network of communication between the hypothalamus in our brain, the pituitary gland in our brain, and the adrenal glands on top of the kidneys.
The short summary is that stress leads our brain to release chemicals like vasopressin and corticotropin-releasing hormone. After traveling through our bloodstream from our brain to our adrenal glands, these chemicals tell the adrenal glands to release chemicals like adrenaline and cortisol. As anyone who has experienced a flight/fight/freeze response in extreme fear knows, adrenaline and cortisol both can have strong effects on the brain and body (fast breathing, fast heart rate, increased alertness, dry mouth, and other things).
The stress response is great in the right contexts since it helps us survive. However, extreme or prolonged stress can disrupt the HPA axis in a way that contributes to things like heart disease, diabetes, fatigue, immune disorders, and depression. I’d also recommend watching [this](https://m.youtube.com/watch?v=eYG0ZuTv5rs) video or reading the book *Why Zebras Don’t Get Ulcers* by Robert Sapolsky (an expert on stress in the brain) if you want to learn about the biology of stress more deeply.
I was about to comment on why, but people here have described it all perfectly. If you want some pictures to explain it further or easier, google: sympathetic vs parasympathetic nervous system. There are great comparisons on google images and you will see and recognize the physical aspect of it all very easily. Hormones have very powerful effects on the human body. When you’re on a roller coaster for example you kind of “force” your body to release the hormones that make you enter “fight or flight”, the sympathetic nervous system. It’s very physical, even though you think it’s your brain playing tricks on you.
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Sorry, I need to ask to clarify and put in simpler terms of what people are saying:
So the “stress” or pain in my chest area is not just me imagining it, but a physical reaction? (I don’t have high blood pressure and heart diseases, yet.)
Ex. When I feel hurt emotionally/breakup, my heart hurts literally.
Ex. When I procrastinate and can’t focus on finishing schoolwork, I feel a clenching feeling in my chest.
So bodies and minds constantly work cooperatively and things like stress are an overlapping thing. For example, stress could be primarily triggered by a mental input (say I’m thinking through something and that causes me to realise I’ve got a major problem paying my bills) or a primarily physical input (I see and feel that I am being physically attacked) and in both cases stress (or, more helpful, a “stress response”) is triggered.
{Note that I said primarily because this distinction doesn’t really hold up beyond our own perceptions. I’ll return to this later}
So the stress response, however it is triggered, leads to changes in the hormones in our bodies. These guys are system-wide messages that impact brain and body. To get an idea of what that means, imagine the fire alarm going off in a large building with a good evacuation plan. Everyone hears the same alarm, but people with different roles react differently:
Many workers evacuate via the nearest exit.
The supervisor of each floor dons a hi-vis and sweeps the floor ensuring everyone is out before evacuating themselves.
A disabled worker with a evacuation assistance plan goes to the designated place.
Workers who are have trained in evacuation assistance go there also and assist the disabled worker.
The building manager goes to the alarm panel and analyses where the fire is.
Et cetera. They all hear the same sound but react differently. Likewise, the same stress-related hormone travels all around the body, triggering different reactions in different places. So whatever causes that hormone to be released, the effects will be the same, much like how the initial reaction to a fire alarm will be the same regardless of whether it was set off on first floor, top floor, by an automatic detector or by someone hitting the alarm panel.
So, why does a human have one alarm system in this way, and not a more nuanced reaction? Theres not a perfect answer there, but these are significant factors 1) Until recently, we had no need for it, because anything stressful needed this whole package of reactions. 2) It’s an automated system and there’s only so much you can complicate those anyhow. 3) {And this is back to the earlier point in curly brackets} the mind and body are much more joined-up than we feel like they are, so in reality everything is triggered by a mind/body combo. That realisation about my bills? Sensory input such as reading my bills with my eyes (even if it was at an earlier point in time) gave me the information that I thought through and got stressed about. Realising I was being physically attacked? My eyes and pain receptors only ever provided data, it was my brain that put together that I was being attacked, rather than feeling pain for another reason.
It’s kind of an evolutionary leftover.
Your stress response is part of your fight or flight mechanism. You come under attack and your body prepares itself to fight or escape: Your heart rate picks up, you breathe harder and faster, your blood pressure increases, your blood stream is flooded with adrenaline… all the things you need to make you more alert, more resistant to pain, able to fight harder or run faster.
The problem is our fight or flight response evolved to deal with physical threats like predators. Short term crises. As cavemen we were born, we hunted and foraged for food, we reproduced and died. Our stress response was perfectly suited to that sort of lifestyle.
Today, most of our stress comes from non-physical factors, things that last way longer than it takes to stick a spear into a wolf or run like hell from a lion… and our stress response can’t tell the difference between being physically threatened and getting an unexpected bill we can’t pay, or worry about losing our job because we heard our company is downsizing.
Basically, think of your body’s stress response as gunning a car’s engine and hitting the NOS. It gives a massive increase in performance, but the engine isn’t designed to take that amount of stress for long periods of time
High levels of stress trigger cortisol release in ur body, and as you experience prolonged periods of stress that cortisol is constantly flowing. Prolonged cortisol exposure like that actually kills immune cells, thereby weakening the immune system overall and that’s why you become more susceptible to diseases (Also! Ppl can experience stress in different ways, I know personally my stress is felt through my stomach. I lose my appetite and simply cannot eat, and I have to go to the washroom constantly. I notice this happens a lot when I’d be studying for an exam or prepping for a test that day, and then as soon as I’m sitting and writing I literally could feel the stress dissipate and my stomach unclenches and the hunger growls start). Others may experience that familiar chest pain feeling or just overall an unwell feeling. Stress is definitely a killer, it’s about learning to moderate the stressors in your life and working to manage it so it doesn’t run your life!
None of these responses seem at the ELI5 level. Let me try:
“Stress” is your brain thinking there is a threat and telling your body “do what you have to so you can get through *right now* and we’ll sort it out later.” So your body floods itself with chemicals that it thinks will help you overcome whatever threat the world has thrown at you – this is when people talk about “super human strength” for example.
The goal of this is to fight off a bear or out run another predator. These chemicals that get dumped into our body are highly toxic to us in the long run, but what does that matter if you die to this threat *right now*?
The issue for public health is that your brain is setup for living in the wild and doesn’t know that an unexpected meeting with your boss is not a threat to your life. So now we have a situation where we are constantly dumping toxic chemicals into our bodies for prolonged periods which causes all the problems you mentioned.
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