Understanding Pain: Why Do We Hurt?

Have you ever had an ulcer in the mouth, a paper cut, or brain freeze? Pretty painful, right? It’s fascinating how even such small “injuries” can still result in so much pain. Thanks to advances in neurophysiology, we now know that the amount of pain someone feels isn't always proportional to the amount of tissue damage in the body. But why and how exactly do we feel pain, then?

According to the International Association for the Study of Pain, pain is “an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.” It is estimated that 1.5 billion people ー that's one in five people ー suffer from chronic pain worldwide. Pain affects everything in someone's life and everything in someone's life affects pain.  And while there is indeed much that we do know about pain, much remains a mystery.

Pain is an output of the brain designed to protect you. Imagine living in a world where you never felt pain: it would make everyday life extremely challenging, not to mention dangerous. Think of pain as an alarm system. Without it, how would you navigate the world safely? How would you know to pull away from a burning flame, or stop pushing your body to the point of injury? 

Pain isn't triggered to tell you where there is physical damage in the body, nor to inform you on the amount of damage. In that sense, it is quite imprecise. Pain is there to protect you, to alert you that something isn't right, and tell you that you need to stop or change what you are doing so you don't end up getting hurt or making an injury worse. 

Pain is only one of the body's protective mechanisms. Your brain has other ways of stopping you in your tracks and getting you to pay attention to what's going on. Think of muscle weakness, emotions such as fear and anxiety, adopting a protective posture, and even holding your breath. Those are some of the ways your brain communicates to you that something is amiss and needs changing. These factors also impact how much pain you will be in. 

But how does pain actually emerge into consciousness?

The body contains over 70 kilometers of nerves, connected like a network of roads that transmit information from the body to the brain and the brain to the body, via the spinal cord. This happens 24 hours a day, every day, at incredibly high speeds, beneath your level of consciousness. These nerves are located everywhere in the human body. They’re in the skin, muscles, joints, spinal cord, and organs. Nerves have sensors (think of them as reporters) in them that provide feedback to the brain about your state, including that on your temperature, level of movement, state of immunity, your blood flow, stress levels, and also any perceived danger. They are what allow you to not only regulate yourself, but also to taste, hear, move, and see, for instance. Contrary to popular belief, while there are pain sensors in the body, they do not send pain signals to the brain. Rather, they send danger signals to the brain, whose job it then is to decide whether this danger is important enough to warrant pain.  

All of these various messages are vying for the brain's attention all the time. The job of the brain is to sort through all of the information it receives, and evaluate what the priorities are and where your attention is demanded in that instant. In that sense, think of the brain as an editor-in-chief who is putting together all of the pieces of a puzzle as they put together a story ー and that story can be more or less accurate. Once the brain has made sense of what is happening, the response travels back from the brain to the spinal cord and into the body. 

Danger signals are high priority signals. Pain nerves react to mechanical, thermal and chemical stimulation. For example, when you jump in the shower and the water is scalding hot, that painful sensation causes you to immediately change the temperature to a cooler setting. When those types of nerves get excited enough ー and it does take quite a bit for them to get excited ー they will send some very fast danger signals to the brain via the spinal cord. When the signal reaches the brain, the decision is made whether there will be pain or not. If something else demands your attention at that moment ー for example, if you are trying to escape a house on fire and have burned yourself in the process ー then you may not feel any pain until the brain decides that it is a “now” priority, e.g. something you would deal with when you are safe. If the answer is yes, however, pain will emerge into your consciousness, lighting up between 200 and 400 different parts of the brain.

Pain isn't just a sensory experience, it is also an emotional one. Think about the times you’ve screamed when you felt pain, or you got angry, or maybe even laughed. In that sense, chronic pain can lead not only to physical decline, but also to emotional challenges, like anxiety and depression. And it isn't just pain that can lead to an emotional reaction: powerful emotions, such as unresolved traumas for instance, can also be felt as pain, creating a noxious sensory reaction. Research has suggested that there is so much overlap between physical and emotional pain that sometimes, it's hard for your brain to distinguish between the two, and how intensely you can feel it.

The brain is extremely sophisticated and complex, making pain difficult to fully comprehend. Your experience of pain will be affected by all of the information your brain is constantly sorting through ー your past experiences (such as previous injuries in the same area), predictions of the future, how much you've slept, your stress levels, your mood, and so on. When pain persists for too long and turns into a chronic issue, what started as an injury in the body then becomes an issue with a changing nervous system that has become more sensitive, and keeps on producing pain long after the physical body has healed. As time goes on, these nerves become more easily stimulated, and it takes less and less for them to fire signals to the brain. What would not have elicited a pain response in the past now does ー and because pain demands your attention (to change what you are doing, or stop what you are doing), your focus remains steadily on what you are feeling. It then becomes difficult to think about anything else. You are in pain, so you stop moving ー but because you stop moving, you are in pain. This Catch-22 makes life hard, and it can feel like you are doomed to just “live with it”.

The good news is that there is hope: Pain is not immutable. If the nervous system can change to be more sensitive, it can also change back. It's tough, and it takes time, but it is not impossible. Remember that behind the pain, there is a human being, and their pain is real. When we look at the whole person, instead of only at their diagnosis, healthcare providers and patients can take a more active role in the healing and recovery process. This is the idea behind the biopsychosocial model of pain. It is important to note that the aim isn't always to erase pain. Sometimes, that will simply be impossible. Although it isn’t always easy, there are ways to cope with physical pain in order to become more active again ー and in doing so, starting to enjoy life to the fullest. By empowering a person with some practical tools to manage their pain, as well as educating them on what pain is (and what it isn't), there is a better chance for them to take charge of it, and change the way they perceive it.

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All of the content on our website is thoroughly researched to ensure that the information shared is evidence-based. For more information, please visit the academic journals and other resources that influenced this article: Assessment Of Pain: Types, Mechanism And Treatment; Chronic Pain And The Health Of Populations; Understanding Pain: Exploring The Perception Of Pain; Contributions Of Psychology To The Understanding And Treatment Of People With Chronic Pain: Why It Matters To All Psychologists; Pain and Emotion: A Biopsychosocial Review of Recent Research.