How Pain Works: The Biopsychosocial Model of Pain.Feb 22, 2020
We have more than 400 individual nerves in our body, all connected like a network of roads.
They each have a bit of electricity running through them, and their job is to monitor our body and inform our brain of anything going on by sending electrical impulses. These electrical impulses act as an alarm system that alerts our brain to the possibility of danger.
The particular nerve endings that do this are called nociceptors. Nociceptors’ job is to detect danger in our tissues and to send that message into the spinal cord and up to the brain.
Our brain takes the information from our nociceptors and starts to ask questions.
How dangerous is this, really?
How safe am I in the context of my current environment?
How much stress or worry am I dealing with?
What are my beliefs around pain?
How does this danger potentially impact my family relationships or my ability to get work?
These questions are asked and assessed in the blink of an eye, and based on the answers to these questions, we either will feel pain or we won’t.
Pain is an output from our brain, not an input from our tissues. Our tissues merely provide a danger signal. Our brain assesses that danger signal in the context of everything else we have going on in our lives, and determines the output as such.
This is called the biopsychosocial model of pain. Bio means the danger signals we receive from our nerves. Psycho means the beliefs we have about pain, our lives and our place in the world. Social means how we are integrated in our families, careers and relationships. Pain is a multifactorial experience that takes into account all of this and more.
This explains why two people who have the same danger signals--let’s say they are both stung by a jellyfish--will have potentially very different pain responses.
If Person A is stung in the midst of being swept away in a large current, it may be that they won’t even realize they’ve been stung until they are safely back on shore. Their brain may temporarily override the danger signals of the sting to make escaping the current a higher priority.
On the other hand, Person B might be wading on the shoreline and almost instantaneously feels the pain of a jellyfish sting, especially if they have a big event they are planning to attend later and are also in the midst of worrying about whether they’ll be laid off at their job the next week.
When we understand that pain is an output from our brain, not an input from our tissues, we are in a better position to contemplate pain oddities. For instance, does pain always mean there is something wrong with our tissues? And how can we explain the pesky nature of chronic pain?
Pain and tissue damage are poorly correlated.
Non specific low back pain is one of the most common complaints we have as a culture. But here’s something interesting for us to consider: Many people who have back pain have no corresponding tissue damage; AND, many people who do not have back pain actually have tissue damage.
What can account for these differences?
Could it be that our individual biopsychosocial factors are a primary influence in whether we do or do not feel pain? Could some of our pain be from highly sensitized nerve endings rather than actual tissue damage? Could tissue damage be a smaller piece of the pie than we might originally conceive?
What this illustrates for us is that pain and tissue damage are poorly correlated. This means that when someone is in pain, we can’t automatically assume that the reason for the pain is because there’s something wrong with their tissues. What’s even more interesting is that the longer the pain persists, the weaker the correlation between pain and tissue damage. In other words, when pain becomes chronic, it becomes potentially more complex.
Chronic Pain vs Acute Pain
In some ways, acute pain is easier to understand. There’s a clear causal connection: I stepped on a nail and now my foot hurts. There is legitimate tissue damage which may take ~4-6 weeks to heal. During that time, I will take the necessary steps to see my doctor, get a tetanus shot, bandage my wound appropriately, and modify my movement patterns. This, combined with my tissue’s healing, will usually be enough for my nerves to desensitize back to their normal electrical charge and for my brain to discontinue the output of pain. In two months, I’ll be running around like nothing ever happened. What nail?
But chronic pain is different. It persists. It may be triggered out of seemingly nowhere. I’m sitting at my computer, there’s no threat in sight, and yet at 2:55 this afternoon I start to feel a searing pain near my right shoulder blade. If that wasn’t weird enough, this is not the first time I’ve felt this pain. I’ve felt this pain on and off for the last 6 years. Sometimes it triggers while I’m driving, sometimes while I’m at my desk, sometimes when I’m in a heated misunderstanding with a loved one. Sometimes it will trigger on and off for an hour, sometimes it will persist without disruption for days.
And it’s not just muscles that we might experience chronic pain in. It could be organs or joints or various other connective tissues. But just because the threat is less obvious doesn’t mean that it’s not there. Pain is always a request for change, it’s just that acute pain often has a more obvious pathway to make that change, whereas chronic pain is a bit more mysterious.
What if our chronic pain is a request to change something less obvious in our biopsychosocial construct?
With chronic pain, the biological factor might not be as obvious as an external threat to our tissues. Perhaps it’s an internal biological factor, like what we’ve had to eat that day, or whether we’ve moved our body recently or often enough. Maybe the psycho factors have to do with our belief systems about ourselves and our environment. It could be that the social factors have to do with the quality of our relationships and the fulfillment we experience at our job. We won’t know until we start experimenting and changing the factors that go into our brain’s decision to output pain.
This example of chronic pain on the inside of the right shoulder blade is not an arbitrary example. This is an example from my own life that I have spent years trying to understand and influence. This pain used to be persistent to the point of lasting for weeks and months at a time. Nowadays it’s less intense, it triggers less frequently and it lasts for shorter periods of time. What did I do to influence this? I’m not really quite sure. I started strength training. I stopped sitting at my desk for undisrupted 8-hour chunks. I generated more peace in my relationships with others. I dismantled some psychologically taxing belief systems that weren’t based on facts. I started cross-training my yoga practice. I leveled up my diet to introduce more fats, proteins, fiber and overall food variety. I picked up new professional skills. I found what I perceive to be job stability. I used pain medication when it became unbearable. I learned more about pain science.
I can’t say for certain that any of these factors did or did not influence my change in pain. And I can’t say what factors will influence yours. All I know is that pain is more influenceable than I originally imagined. I originally imagined pain to be a fixed experience starting and stopping in the precise areas where I experienced it.
For anyone experiencing pain, I recommend whatever next step seems right to you. Maybe you’re a self-learner and it’s time to educate yourself. Maybe you feel safer in the company of professionals, and it’s time to find a doctor who specializes in pain science. Whatever your decision, I hope this article serves to bolster your optimism that a brighter future is possible.
My scope of practice begins and ends with teaching movement. What I’ve found over the past 10 years is that movement is connected to many other systems of knowledge and I’ve found pain science to be incredibly useful in my own life. I’ve seen how a small morsel of understanding can positively impact the lives of my students, some who will walk into the yoga room and say things like, “I just have a bad back,” or, “I can’t do x,y and z anymore because of my hip”. It’s amazing how many beliefs we have regarding pain that are not based on facts. And it’s amazing how things can change for the better when we start to investigate some of that.
If you’re looking for a system of movement that takes into account things like pain science, exercise science and movement psychology, stick around! That’s what we’re all about at Yoga In Your Living Room.
- Painful Yarns, by Lorimer Moseley
- Why Do I Hurt?, by Adriaan Louw
- The Truth About Back Pain: A Biopsychosocial Approach to Treatment, by Shelly Prosko
- The Biopsychosocial Model Helps Explain Complex Difference in Pain, by Pauline Voon
- Non-specific Low Back Pain Exists. You Just Don't Want To Admit It, by Greg Lehman
4 Basic Pain Science Concepts For Yoga Teachers, Part 1, by Jenni Rawlings
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