Pain is not just a message from injured tissues to be accepted at face value, but a complex experience that is thoroughly tuned by your brain. Pain is as volatile and hard to predict as weather, jostled by countless unknowable systemic variables — but especially the potent perceptual filters of the brain. The results are often strange and counter-intuitive: fascinating cases of trauma without pain, and pain without trauma.
The science is clear: the brain makes pain. Pain is 100% Brain Made®, like everything else in life.1 Threat signals from “insulted” tissues are only one factor of many that the brain considers before creating an experience of pain. The brain often even over-protectively exaggerates pain, sometimes sounding alarms so persistently false that it can become a much bigger problem than whatever caused the alarm in the first place: “sensitization.”
Does all this brain involvement mean can we think pain away? Just how much power does the mind have over pain? Can confidence and education cure? The long answer is on another page, Mind Over Pain. Here’s the short answer: pain is mostly up to our brains, not our minds, and it’s extremely hard to boss our brains around. There are some opportunities to “hack” the pain system, but you have to understand the system, and that’s what this article is for.
Many discoveries about the physiology of pain23 have been painfully slow to reach the public, or even health professionals. This is useful stuff, and it needs to be shared.
The main take-home lesson from weird science of pain is that we desperately need to stop thinking of pain in terms of always reflexively and proportionately coming from insulted tissues: “It’s all coming from the ____, I know it!” It almost never is.4 Pain is not a reliable sign of what’s really going on. It’s a witch’s brew of different factors, complex by nature (not just coincidence or bad luck). At the very least, pain always has a layer of brain-generated complexity. At the worst, the pain system can malfunction in several colorful ways, causing pain that is much more intense and interesting than just a symptom — sometimes the pain is the problem.
The biology of pain is never really straightforward, even when it appears to be.
“Reconceptualising pain according to modern pain science”, Lorimer Moseley
One of the principle qualities of pain is that it demands an explanation.
Plainwater, by Anne Carson
Perception is the brain’s best guess about what is happening in the outside world. Perception is inference.
Scratching an itch through the scalp to the brain, by Atul Gawande
This well-produced short video neatly summarizes many of the key points of the content of this article. Great explanation of how pain works! (But their advice about what to do with that knowledge is off-key — more on this later in the article.)
Another fine video “summary” of a different sort: this hilarious TED talk about a snake bite and pain neurology. No, really, you will actually laugh! It’s like stand-up comedy. Australia’s Lorimer Moseley, Professor of Clinical Neurosciences and tireless pain researcher, is one of the best public speakers I’ve ever seen — a must-watch for anyone with chronic pain, and the professionals who care for them. Does he say “groovy” just a couple times too many? Maybe! But it is groovy … mate.
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Ramachandran said that “pain is an opinion” — which sounds like a flaky New Age mind-over-matter theory. But Ramachandran is no mystic or guru: he is a neurologist and scientist. This passage is mainly known for the first few words, a pithy statement of the modern understanding of how pain works:
Pain is an opinion on the organism’s state of health rather than a mere reflexive response to an injury. There is no direct hotline from pain receptors to ‘pain centers’ in the brain. There is so much interaction between different brain centers, like those concerned with vision and touch, that even the mere visual appearance of an opening fist can actually feed all the way back into the patient’s motor and touch pathways, allowing him to feel the fist opening, thereby killing an illusory pain in a nonexistent hand.
Phantoms in the brain, by VS Ramachandran and Sandra Blakeslee
He then tells the story of an extraordinary cure of a man with phantom limb pain, tortured by agony in a clenched fist that was not there. With a clever arrangement of mirrors, Ramachandran created the illusion that the man’s amputated arm was restored — a sort of “virtual” limb. The mere appearance of his phantom hand opening and closing normally cured his agonizing “spasms.” He felt better because of the illusion that he was better — because he thought he was better. The mirror-cure of phantom limb pain is one of the most curious anecdotes in all of pain science. In all of medicine, in fact.
Since then, “mirror therapy” has been studied and applied in many ways. A good quality 2007 study showed that mirrors aren’t actually necessary to achieve this effect.5 Mirror therapy is probably just a “fun” way to visualize healthy movement — which also works quite well without a mirror!6
Stranger still are tales of severe pain without injury, illustrating that pain can be entirely in the mind. (Technically, it always is.) One of the strangest of these was reported in the British Medical Journal in 1995:
A builder aged 29 came to the accident and emergency department having jumped down on to a 15 cm nail. As the smallest movement of the nail was painful he was sedated with fentanyl and midazolam. The nail was then pulled out from below. When his boot was removed a miraculous cure appeared to have taken place. Despite entering proximal to the steel toecap the nail had penetrated between the toes: the foot was entirely uninjured.
JP Fisher, senior house officer, DT Hassan, senior registrar, N O’Connor, registrar, accident and emergency department, Leicester Royal Infirmary7
His pain was a “nocebo” — the opposite of a placebo.8 Extreme examples like this are rare, but probably not as exotic as you might think. More to the point, even if they are rare, for every case like this there must be hundreds more where the injury is real but the patient is convinced that the damage is much worse than it really is — with proportionately exaggerated pain. And indeed there is evidence of this: in a 2012 experiment, for instance, fear of pain made people more sore for longer after a workout.9
Happily, it also works the other way: people may feel much less pain than they “should” when they are confident for any reason, such as not realizing how bad the damage is.
Injury and pain are not in lock step with each other. And yet that is exactly what nearly everyone assumed for a long, long time. And many professionals, even though they may “know” better, often seem to forget how powerfully pain is influenced by perception, context, and meaning.
What is surprising is how malleable pain signals are—how readily the intensity of a pain signal is changed by the sensations, feelings, and thoughts that coincide with the pain. … The brain is not a mindless pain-ometer, simply measuring units of ouchness.
Why Zebras Don’t Get Ulcers, by Robert M Sapolsky, 187, 193
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For most of the history of medical science, pain was believed to work more or less the way the French philosopher René Descartes described it: a simple signalling system.
- The flesh is wounded. (“It’s just a flesh wound!”)
- Nerves send an unambiguous message to the brain about the damage. The intensity of the message is directly proportionate to the severity of the injury.
- The brain interprets that message at face value — that is, if the message says, “There’s some bad damage here,” we believe it.
Based on this model, almost everyone still — today, in 2021 — assumes that any message sent to the brain by a certain kind of nerve will always cause pain. Health care professionals everywhere still believe that the nerve is “sending pain,” that the signal is pain — and therefore these nerves are habitually called “pain fibers” and their messages are called “pain messages,” an equivalence between signalling and pain baked right into the language. This is wrong! And it’s worse than an oversimplification.
The labeling of nociceptors as pain fibers was not an admirable simplification, but an unfortunate trivialization under the guise of simplification.
The relationship of perceived pain to afferent nerve impulses, by Patrick Wall and SB McMahon, 254–255
The first dent in this paradigm came in 1965 with the discovery of the gate control theory,10 which showed that other inputs can pre-empt pain — Counterstimulation — the first strong evidence that pain isn’t an inevitable, predictable response to noxious stimuli. Ever since, it has become increasingly clear to pain scientists and neurologists that the simplistic pain-fiber model is hopelessly inaccurate. In fact, they call it “the naïve view”!11 Even microscopic worms with only two trouble-detecting nerves, compared to our billions, have context-sensitive pain experiences.12 Even their pain is an “opinion,” an interpreted experience. And of course it makes complete evolutionary sense. Pain is clearly more useful as an experience when it is “smarter.”
So the way pain really works is much more complicated, interesting, and in some ways useful. A nerve should never be called a “pain” nerve. It doesn’t detect “pain.” It only detects some kind of stimulus in the tissue … and the brain decides what to make of it, how to feel about it, and what to do about it, if anything.
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Pain is often less painful when we are confident that we are safe. This was demonstrated early in the history of pain research by a famous paper about wounded soldiers in WWII: they experienced surprisingly little pain for the severity of their injuries, probably because they were just so glad to be off the battlefield.13 Ever since, researchers have been trying to understand just how that actually works, and these days we have a rough outline of how that works.
The brain is not just a passive, gullible receiver for whatever messages the peripheral nerves send upstairs. And, if you think about it, it’s kind of strange that we would ever have thought of it that way, because this is, after all, the brain we’re talking about: seat of consciousness, the generator of your reality. Brains critically evaluate all the danger messages and put them in context before deciding how seriously to take the situation.
Once a danger message arrives at the brain, it has to answer a very important question: “How dangerous is this really?” In order to respond, the brain draws on every piece of credible information — previous exposure, cultural influences, knowledge, other sensory cues — the list is endless.
Pain really is in the mind, but not in the way you think, Moseley (TheConversation.com)
As if that didn’t complicate things enough, once your brain has made up your mind, it also sends messages downwards that actually affect the function of the peripheral nerves.14 Thus everything that hurts involves a conversation, a sort of debate between the central and peripheral nervous systems. It could be dramatized like this:
|NERVES||Got problems here! Bad problems! Red alert!|
|BRAIN||Yeah? Hmm. Okay, so noted. But you know what? I have access to information — sorry, it’s classified, you’ll just have to take my word for it — that suggests that we don’t have to worry about this much.|
|NERVES||I’m telling you, this is serious!|
|BRAIN||Nope, I don’t buy it.|
|NERVES||Look, I may not have access to this “information” you’re always talking about, but I know tissue damage, and I am not kidding around, this is a credible threat, and I am going to keep telling you about it.|
|BRAIN||Actually, you’re having trouble remembering what the problem is. You’re going to send me fewer messages for a while. Also, these aren’t the droids you’re looking for.|
|NERVES||Uh, right. What was I saying? Gosh, it seems like just a second ago I had something important to say, and it’s just gone. I’ll get back to you later I guess …|
The brain can boss the nerves around, tell them how sensitive to be. When anxious, the brain might request “more information” from the peripheral nerves, ordering them to produce more signals in response to smaller stimuli. Or it might do exactly the opposite. There is extensive recent evidence that the peripheral nerves can even physically, chemically change, perhaps in response to brain requests, tissue conditions, or both. To extend the analogy, this isn’t just twiddling the volume knob, but changing the equipment, changing the signal before it even gets to the “amplifier.”
(Just for fun, have a look at the complex version of that diagram. SHOW)
In short, messages don’t just go up to the brain, they go down. This two-way functionality in the pain system is the main difference between modern pain science and old-school pain science.
But most of the modulation is probably central: we only feel what our brains allow us to feel. Even “loud” sensory messages can be filtered down to almost nothing by the central nervous system … or, conversely, “quiet” sensory messages can be amplified. The quality and intensity of the final experience is clearly the product of an elaborate set of neurological filters.
Perhaps many patients whom doctors treat as having a nerve injury or a disease have, instead, what might be called sensor syndromes. When your car’s dashboard warning light keeps telling you that there is an engine failure, but the mechanics can’t find anything wrong, the sensor itself may be the problem. This is no less true for human beings. Our sensations of pain, itch, nausea, and fatigue are normally protective. Unmoored from physical reality, however, they can become a nightmare … hundreds of thousands of people in the United States alone suffer from conditions like chronic back pain, fibromyalgia, chronic pelvic pain, tinnitus, temporomandibular joint disorder, or repetitive strain injury, where, typically, no amount of imaging, nerve testing, or surgery manages to uncover an anatomical explanation. Doctors have persisted in treating these conditions as nerve or tissue problems—engine failures, as it were. We get under the hood and remove this, replace that, snip some wires. Yet still the sensor keeps going off.
So we get frustrated. “There’s nothing wrong,” we’ll insist. And, the next thing you know, we’re treating the driver instead of the problem.
Scratching an itch through the scalp to the brain, by Atul Gawande
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We cannot trust our eyes, and we cannot trust our pain. Pain is a lot like these amazing illusions — that is, it is warped by our expectations and point of view:
Unlike these clever models, though, we can’t turn it around to see what’s really going on. And trying to see through the illusion, trying to believe that there’s nothing much actually wrong with our tissues (often true), is even more difficult than seeing through these illusions. But that challenge is what recovery is all about: trying to change our expectations and point of view with interesting new sensations and movements.
Examples are helpful. Demonstrations that punch through the illusion.
In the sections ahead, we'll look at interesting scientific studies and clinical cases all showing different perspectives on how the brain modulates pain. In some cases, they also show how it is directly or indirectly influenced by our minds. For example, being in love influences pain, and being in love is richly psychological — but also infamously uncontrollable.
Thanks to a quirky 2014 study, science has confirmed that being in love relieves pain — a wonderful example of the potential power of the mind over pain.15 Falling head-over-heels is not exactly a convenient solution. As researcher Dr. Sean Mackey put it, “We can’t give you a prescription for love” — not one that’s easy to fill, anyway. But we can work to give love more of a chance to grow and thrive. You can’t benefit from the pain-killing effect of love if you aren’t in love.
Closely related: pain is also muted when romantic partners hold hands. Aw.16
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If you view a painful hand through a magnifying glass, it will actually get more swollen and inflamed — that is, if you make it look bigger, it will feel like a bigger problem.17 And the reverse is true too! Use optics to make it look smaller, and swelling will go down. Incredible, right? Jedi pain tricks! But … do you have a de-magnifying glass handy? Where do you buy even one of those, let alone a big one? (They really are hard to find. How about looking backwards through binoculars? Not a great solution.18) And what happens if the pain isn’t in a place that’s so easy to de-magnify, like your low back?
The de-magnification trick is dang interesting, but it’s obviously not a practical approach to most pain. The effect is real under the right circumstances, but trying to use it as a treatment is like trying to take a magician’s trick home with you.
Maybe someday virtual reality tech will make “visuotactile illusions” like this a lot more accessible and convenient. A nifty proof-of-concept study demonstrated that a couple of other illusions can reduce osteoarthritis pain by up to 40%, at least temporarily.19 So what visual sorcery can kill more pain than any other known treatment for that condition? Two similar illusions, using virtual reality goggles to make it look like the knee was either shrinking or stretching. 😜 Whoaa, duuuuude …
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Getting an injection actually hurts less when you don’t watch.20 Out of sight, out of mind: if the brain can’t see the threat, it is less sensitive to it. That’s interesting, and like the magnification/stretching/shrinking experiments, it clearly demonstrates that the brain modulates pain and, in that circumstance, we can modulate it. It’s easy to look away from a needle, but with most chronic pain, what is there to avoid looking at? We usually can’t see the threat.
Although it is technically the brain’s prerogative to ignore painful signals from your tissues, that doesn’t mean that there’s any way we can convince it to do so — if there is a destructive disease process going on, for instance, the brain will usually not ignore those signals! The pain system evolved to report problems, and you can count on it to do so most of the time.
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This isn’t about pain, strictly speaking, but it’s too relevant not to share. This is a photo of three-legged cat Isaac, trying to scratch himself with his missing leg:
Now a little to the left …
That has got to be super frustrating! The pathetic futility of Isaac’s scratching does not stop his brain from trying. Poor little guy! His brain has a picture of how things should be, and he acts accordingly. The impulse is like a freight train, irresistible even when it’s blatantly ineffective.
So it often is with pain: if the brain believes there’s a threat, you’re going to hurt, no matter how pointless it is or how intensely you focus on trying to have more reasonable and rational sensations. It’s mostly just not up to you. But that doesn’t mean that we’re completely powerless. Mind has some influence over brain. Below I will continue with some practical ways we might be able to “hack” pain neurology a little bit.
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This one’s from my own medical history, in the aftermath of corrective eye surgery in 2011, and some odd consequences shed good light on how pain works: insight from eyesight. Recovery went well initially; a few weeks later, my optometrist couldn’t even find any sign that anything even happened to my left eye. No laser tracks. No remaining signs of recovery. It was ahead of schedule.
But my right eye was a bit blurry, and it ached. In reality, it was also healing on schedule — but it was lagging behind the ahead-of-schedule left, and it was freaking me out a bit. Get a load of what my science-minded optometrist said (paraphrasing) when I told him about this:
People’s eyes often hurt when they think there’s something wrong with them.
That demonstrates that “pain is an opinion” rather well. My optometrist described the following scenario (paraphrasing):
Someone can “discover” an eye problem they’ve had for twenty years and start hurting. They accidentally cover one eye while watching television, happen to notice that the vision in the free eye is a bit off. It’s been off all along — almost everyone is at least a wee bit astigmatic, but the brain completely takes care of that when both eyes are open. But if they notice it with an eye covered, a week later they’re in my office complaining of blurred vision and an ache.
Fascinating. I was paying close attention to my vision in the aftermath of the surgery — probably too close. I “discovered” that the right wasn’t as good as the left, and started checking it even more obsessively. And so it started to ache. And yet it’s only problem was being less awesome than my left. Good grief.
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Sensation and pain are nothing if not mercurial. On the one hand, we can be driven half out of our minds by a bit of beef wedged between a couple teeth. Or, stuck right in the other hand, a large piece of metal can be painless for 50 years. Like a turn signal lever.
Art Lampitt got one of those embedded in his arm in a car accident long ago. What with all the other injuries, no one noticed. It didn’t give him any trouble until recently. His arm began to ache and swell and an x-ray revealed a strange, thin third arm bone.
“I was hoping it might be shiny still,” he said in an interview with CBC Radio One’s “As It Happens,” but it was badly corroded — perhaps the reason it finally caused some symptoms, but who knows.
I love medical marvels that challenge our preconceptions about what will hurt. It’s noteworthy that it didn’t hurt for decades — because if that’s possible, just imagine how unpredictable the symptoms of a little arthritis can be — but it’s also noteworthy that it did start to cause trouble eventually. It’s a great example how pain is weird.
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This next example is extracted whole from Marni Jackon's superb book, Pain: The science and culture of why we hurt. This is an amazing anecdote about the power of perception, and what I want to highlight here is that this wasn't just a case of medical fear and panic: it was a painful experience.
“There are psychic factors involved in every patient’s complaint of pain,” [Bill Livingston] wrote. He tells a story of one midnight emergency to illustrate his point.
A woman called him to report that her husband had just had a “massive bowl hemorrhage and was in a state of collapse.” Just before bed, he had felt some cramping pains and hurried to the bathroom. Then she heard him calling her name, followed by the thud of him falling to the floor. She found him unconscious, white-faced, and covered in sweat. And in the toilet there was a quantity of bright red blood.
Livingston told her not to flush the toilet and rushed over. He found the man lying on the bed, conscious, but in pain. Where does it hurt the worst, Livingston asked. “All over,” the man whispered. He went on groaning as his wife said that he had been in fine spirits and food health, until he had gone to the bathroom.
Livingston examined him, to no avail. Then he went into the bathroom and inspected the alarming-looking contents of the toilet. Beets. Lots of beet fragments. It turned out that her husband had eaten beets for lunch, and little else. Livingston decided that this accounted for the “hemorrhage” and that the man’s state — the pallor, the sweating, and the “all over” pain — had been entirely caused by fright.
The two of them walked back into the bedroom with smiles on their faces, which annoyed the husband, who was languishing on the bed. But when Livingston gave him his diagnosis, the man’s condition improved rapidly. “Within half an hour he was moving about in his usual energetic fashion and offering to pour me a drink if I would stay and chat.”
It hurt all over. Because his brain absolutely believed he was in terrible danger. And no other reason.
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In the weird world of pain, fearing the worst is at least partially a self-fulfilling prophecy: the more worried you are, the worse things tend to do. There are many examples of this, but this is a good fresh one, and I also like the fact that it’s about something people don’t usually as associate with psychology: knee replacement.
Dr. Gary J Macfarlane, regarding a paper on knee replacement results:
“We identified 3 distinct response trajectories in patients undergoing knee replacement. Expectations of pain/limited function and poor coping strategies differentiated the trajectories, suggesting a role for preoperative psychosocial support in optimizing the clinical outcome.”
Although this evidence doesn't show it, it also seems reasonable to assume that the reverse is true: if worry is worse, probably hope helps. So anything at all that increases patient optimism and confidence is a good idea.
It’s also a dilemma for health science reporting and clinicians: truth may be harmful! The discouraging reality of side effects, poor outcomes, and other bad science news — and there’s a bunch of bad news about knee replacement, — will make patients more pessimistic and fearful, and therefore will actually causes worse outcomes. But we cannot lie or conceal the truth, either! Awkward. 🎵 The truth may be problematic, but also unavoidable and essential. There is no easy solution to this dilemma.
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This example of pain weirdness does not have the charming narrative appeal of some of the stories above, like being in agony from mistaking beet juice for blood. It’s abstract, technical, and hypothetical.
But still very cool.
In the beet juice example, we can see a strong element of behaviour in the pain, a a response response to a stimulus, a perceived threat. And behavioural responses to stimuli can be learned. And it’s possible that this is the nature of some chronic pain. What if your brain just kept believing in a threat? What if there wasn’t a doctor who could helpfully reassure you that it’s just beet juice, not blood?
Many perceived threats cannot be dismissed so neatly and convincingly, and they may continue to produce a pained reaction. In other words, some chronic pain might be a “learned response” (classical conditioning) to things that shouldn’t hurt, like Pavlov’s dogs salivating to the ring of a bell. This is a hypothesis. It is plausible enough to be taken seriously, but unproven and strange enough to be rather exotic.
And it gets weirder!
It’s also possible that learned pain can be un-learned — more specifically, “disrupted.” This is is hardly obviously the case: it could be just as impossible as forgetting a traumatic memory. But there might be a way. In the neurology of classic conditioning and memory, responses to stimuli are neurologically “re-saved” every time the stimulus occurs. And that process can be “disrupted.” The hypothetical part is not whether reconsolidation happens or can be disrupted — it does happen, and it can be disrupted, these are established neurological phenomena. The question is whether any of this is applicable to pain, and no one knows the answer to that yet.
Can pain be a “behaviour” in response to stimuli? If so, it can probably be disrupted. That’s the cool hypothesis. That’s the (hypothetical) weirdness.
If so, it’s as much of a “hack” for pain as I can imagine. I discuss it more thoroughly in Mind Over Pain, and more thoroughly still in in Chronic Pain as a Conditioned Behaviour.
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Acute pain usually correlates quite well with tissue damage — although even horrible tissue damage can be surprisingly painless in the right context, that’s the exception to the rule.
Most of pain’s weirdness happens when you enter … The Chronic Zone. As pain drags on, its relationship to actual tissue trouble gets sloppier, and in some cases breaks down altogether. Pain can even cease to have anything to do with tissue damage whatsoever: such patients are effectively hallucinating pain, “false alarm disease.” This phenomenon is broadly known as “sensitization.”21 It’s probably a major factor in most of the pure chronic pain conditions — nasty chronic pain that seems disconnected from any cause, like fibromyalgia or complex regional pain syndrome.
More commonly, chronification of pain involves exaggeration of ordinary pain problems. This may actually be the much bigger problem for our species. Imagine the tragedy of billions of cases of low back pain, headaches, plantar fasciitis — and many others — that are all 20–60% louder than they really “should” be. Not “false” alarms, just obnoxiously and unncessarily noisy ones.
Sensitization really needs an entire article to itself, and it has one: Sensitization in Chronic Pain: Pain itself can change how pain works, resulting in more pain with less provocation. As big as this article is, you can’t really be done learning about how weird pain is until you’ve read that one too. Sorry about that. It’s a big topic!
The chronification of pain is dominated by the concept of sensitization, but there is more to it. Another weird thing about pain, another major wrinkle…
Pain sensation and perception can be badly distorted in various ways, and that is weird and cool, but also relatively rare. We can make pain up out of thin air, like the guy with the nail driven between his toes, but we rarely do. And we can have bizarrely painless trauma — like the soldier who barely feels his wound — but we rarely do. All the famous and fascinating examples are famous because they are rather exotic.
For most people, most of the time, pain is a relatively consistent, predictable, and sensible warning system about tissue danger — just like the “naive view” always assumed. The boring-but-basic reality is that tissue trouble still usually leads directly to pain. Just because that correlation can get messy and break down does not mean that it always does. Pain has to be reliable: that’s why it exists.
Most importantly, not all chronic pain is dysfunctional.
Much is made of the difference between acute pain and chronic, generally assuming that acute pain is accurate, while chronic pain is exaggerated or outright bogus. But there’s another important possibility: accurate acute pain that just keeps happening, a renewable resource, an ongoing credible threat to tissues that the brain should take seriously.
Some causes of persistent pain — a thorn, an old wound, a tumour — are almost too obvious to be worthy of mention. But the cause of persistent pain is often baffling. There is a cause, a “thorn” of some kind, but a largely invisible one. For instance: my friend who had an almost literally invisible tumour pressing on a nerve root, a pathology that could only be seen if you looked in just the right way, with just the right kind of imaging. Until diagnosed, he was treated by more than one healthcare professional as a dysfunctional chronic pain case — but it was actually a clear cut case of chronic-acute pain, not dysfunctional at all, not a false alarm at all, but pain that was definitely not.
It was just hard to diagnose.
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This discrepancy between dysfunctional and functional chronic pain is a huge clinical challenge and another face of pain’s weirdness and complexity. In this case, the weirdness is just as much about our lack of clearly labelled concepts as it is about the nature of pain itself. There actually isn’t even a name for the difference between these two classes of chronic pain! When there’s a persistent or recurring cause of pain, I call it “chronic-acute” pain — but that’s just my informal, descriptive term. A more technical description would be persistent nociceptive pain.
When there’s no known damage, there are two possible explanations for chronic pain (other than hypochondria):
- either there is tissue insult (a source of nociception) that just can’t be identified (surprisingly common I think), or
- the relationship between tissue insult and pain has broken down (also quite common).
And, of course, these scenarios are not mutually exclusive: you can have both tissue damage and a wonky, disproportionate relationship to pain. There’s plenty of overlap. It’s basically impossible to know how much of each is contributing to a given case.
But the existence of chronic-acute pain is an important source of hope and reassurance for many people, because it means that a “thorn” could still be found, and pulled out. I’m speaking both professionally and personally here. I once had a persistent pain with no apparent cause, and I was told by a series of professionals that my only problem was pure pain dysfunction. But then, rather better late than never, the %#!!$& source was found and removed … and that was the end of my pain. Ta da! My “thorn” was found and removed.
So I suffered a year of serious chronic pain with no apparent source that absolutely was positively, strongly correlated with a tissue insult. My brain was not lying. The alarm was not false. There was just a sneaky reason for it.
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100% of the time, pain is a construct of the brain.
Lorimer Moseley, from his surprisingly funny TED talk, Why Things Hurt 14:33
If that is true — and it really is technically true22 — does that mean can we think brain-built pain away? Can our minds un-build pain? Yes and no, because, as Dr. Moseley explains, “Pain really is in the mind, but not in the way you think.”23 This is a good news, bad news kind of thing. I will get to the good news, but let’s get the bad news out of the way first:
It’s not really possible to think pain away in general. Many wise, calm, confident optimists still have chronic pain.
Pain is a motivator. It exists to get us to act. We hurt when our brains reckon we should do something differently, for safety … but safety is not always possible. The nature of the danger isn’t always clear, or avoidable.
And the brain worries too much: from hangnails to fibromyalgia, it overstates the danger (for rock solid evolutionary reasons), and it can’t be overruled by wishing, force of will, or a carefully cultivated good attitude. The brain powerfully but imperfectly controls how we experience potentially threatening stimuli, but I’m sorry to report that you do not control your brain.
But we do have considerable control over the context in which our brain lives. We can change our circumstances. We can improve the odds that our brains will become less concerned about our tissues, and lower the volume of the alarm. It’s not mind over pain in the sense of a neurological “hack” or an impressive act of willpower, but it’s not nothing either.
I explore all the various mind-over-pain possibilities in as practical away as possible in a separate article: Mind Over Pain: Pain can be profoundly warped by the brain, but does that mean we can think the pain away?.
It’s not always clear to healthcare professionals how to integrate the weirdness of pain into their work. Physical therapists, massage therapists, chiropractors, and osteopaths in particular — the freelance, “manual” therapists — have generally been barking up a different tree for several decades: looking for the roots of pain in structure and biomechanics, the paradigm of “structuralism.” And structuralism hasn’t been working out all that well.
So what do you do with the information that pain is an output of the brain? What does in mean for what you do with patients?
Start by not focusing exclusively on “fixing” patient’s tissues. Often the problem is not the tissues, but a pain experience spinning out of control. Even when there is a tissue issue, it’s all too possible that fixing it is just impossible, that all the “tools” (treatment modalities) are largely useless,24 either entirely ineffective or, at the least, less important than then neurology
This can be extremely intimidating. Explaining pain is by far the most well-known strategy for dealing with it, and it seems to sideline clinicians. You may feel like it leaves you little to “do” to or for their patients. Professional paralysis.
The main solution to that feeling is to address the patient’s nervous system. Be kind to it. Help patients remember what it’s like to feel safe and good. Be the source of a positive sensory experience. Choose and exploit modalities not for their barely-there power to change/fix tissues, but for their power to comfort and soothe, to reframe sensory experiences.
And also educate to reassure, independently of whether you “explain pain” or not — though you will find that some pain-explaining is vital for achieving that goal.
And definitely avoid giving patients any new cause for alarm or worry.
When the primary complaint is pain, the treatment of pain should be primary.
Barrett Dorko, Physical Therapist, online discussion, 2010
Many moons ago I started trying to understand and explain pain, gradually producing this article, only dimly aware as I worked that I was re-producing some much more mature ideas.
I knew that modern pain science and treatment has deep roots, insights and research going back to the 1960s and Melzack, gate control theory and cognitive behavioural therapy, but my explaining was eerily similar to a recent and popular “packaging” of pain science known as Explain Pain (EP), from Drs. Lorimer Moseley and David Butler: “a range of educational interventions that aim to change one’s understanding of the biological processes that are thought to underpin pain as a mechanism to reduce pain itself.”25 There’s a book of that name — Explain Pain — and many other interpretions and riffs on the key ideas (like this article). It’s not that I invented my own version of Explain Pain independently, I was just trying to explain pain, you know? Lowercase!
Explaining Pain, according to Dr. Moseley, is about “wanting people to actually understand how and why they can be in horrible pain yet not in horrible danger.”
There have been a lot of misunderstandings about EP. Because explaining pain is tricky. (There are still plenty of unanswered scientific questions, too.) And because EP as a “brand” might be a bit of an over-hyped upstart, maybe given too much credit by too many people too soon — especially the idea that it actually reduces pain, which remains highly speculative. Nevertheless, for the record, here are some key misconceptions about EP …
- Explaining pain is not about managing or coping with pain. That’s another (important) kettle of fish.
- It’s not just about chronic pain. Acute pain needs splainin’ too.
- Explaining pain does not encourage people to move despite their pain — it’s just about teaching them that pain is often “overprotective.” Just because the brain worries too much sometimes doesn’t mean it’s always wrong.
- It’s not about the regulation of “pain messages” or “pain signals,” because there are no such things. It’s about the regulation of danger messages, and how only the brain can amplify or mute pain.
- The point is not to reassure people that pain is “just” a perception and not real (ugh) — it’s about reassuring people that the danger implied by pain may be exaggerated by the brain (or other dysfunction of the whole complex system).
- Many people seem to think that Explain Pain ignores biology, biomedical, and structural factors in pain. Nope: the point of explaining pain is to explain the “it’s complicated” relationship between those things and pain. Tissue damage is real, and pain arising from it is real, but they aren’t exactly in tidy sync with each other.26
- It’s not just about central sensitization (for which there is no known cure). Sensitization is an important sub-topic, but it’s important to explain unsensitized pain too.27 And the explain pain movement is actually rather optimistic (maybe even too optimistic) that learning the right things can actually change pain — even when it’s the product of sensitization.
- “Explain Pain” is not synonymous with “pain science.” The science of pain is the systematic investigation of the phenomenon and biology of pain; it isn’t a formal scientific field, but it is an area of research. Explain Pain is an approach to pain management inspired by new insight into how pain works.
But the mother of all misunderstandings is the popular idea that if pain is an output of the brain, then we must be able to think our way out of it. This is such an important and difficult topic that I've devoted a separate article to it: Mind Over Pain.
That question was asked in a popular Facebook discussion group in early 2020. To be clear, it was not a reference to this website, but to ideas that are explored here (especially in this article), which are regularly mistaken for a treatment method (Explain Pain, either specifically or more generically).
That question attracted a lot of comments, but mine was rather popular, so I thought I’d transplant it to here, slightly edited and embellished for dramatic effect:
And what is “Pain Science” as opposed to the science of pain, exactly? Why capitalize it like a brand? What exactly are we talking about, if not “the science of pain”?
The owner of the domain PainScience.com (hint: it’s me) would really love to know what’s up with this capitalization bollocks. 😉 Because I know for damn sure that my brand is all about “the science of pain,” no capitalization, no modality or methology, no dogma or canon… just good information derived from the systematic investigation of the human experience of pain. That’s it.
If we are talking about the science of pain, then the question is effectively asking if clinicians are paralyzed by… knowing things. Are clinicians becoming paralyzed by the application of science to their work? By a modern and nuanced understanding of how pain works? Maybe they are!
But I’m sure that’s not a bad thing.
It’s true, knowledge can be paralyzing, and this has always been a challenge with evidence-based medicine: it’s hard! It’s the higher road. EBM is indeed harder than what came before. It is easier to just go with whatever witch’s brew of fact and fiction you’ve acquired from experience and mentors. Experience is especially seductive and misleading. But we do EBM not because it is easy, but because it is hard… and because it is better.
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There is no zealot like a convert, and some people get so entranced by the idea that pain is an output of the brain that they seem to deny that tissue state matters at all. If you’ve been frustrated by the advocates of Explain Pain and “pain science” on social media, this section is for you. Yes, sometimes they do go too far!
All pain is indeed completely generated by your brain, technically … but that is the nature of consciousness and perception. Most sensory experiences have strong roots in the world. Which includes the flesh.
Everything is in the brain, but when we want to learn about the universe, we look through telescopes, not brain scanners.
Dr. Rob Tarzwell of One-Minute Medical School. (Ironically, when Dr. Rob wants to learn about people, he looks at them with a brain scanner.)
If you want to know about nectarines, you mostly study nectarines, not the brains that perceive them. If you want to know about that nebula, you use a telescope, not a brain scanner. And if you want to know how back pain works, you are going to have to study back injuries and pathologies as well as the creative, colourful, and dysfunctional ways that brains play with perception of backs. But brains are still usually playing with the perception of something that is actually going on in the “world” of your back — in your tissues.
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About Paul Ingraham
I am a science writer in Vancouver, Canada. I was a Registered Massage Therapist for a decade and the assistant editor of ScienceBasedMedicine.org for several years. I’ve had many injuries as a runner and ultimate player, and I’ve been a chronic pain patient myself since 2015. Full bio. See you on Facebook or Twitter, or subscribe:
- “Pain really is in the mind, but not in the way you think,” Lorimer Moseley, TheConversation.com. In this not-too-technical article, the endlessly quotable Lorimer Moseley summarizes the role of the mind in chronic pain, especially low back pain.
- “Scratching an itch through the scalp to the brain,” Atul Gawande, NewYorker.com. This is a particularly wonderful article, which uses a fascinating and awful medical story — about a woman who scratched through her skull (seriously) — to explain how pain works, just as this article does. It’s a point that a lot of experts are making in a lot of different ways, and more all the time, but this is the best I’ve seen yet: great storytelling and superb reasoning, from Atul Gawande, one of the best medical writers alive today.
- Why Things Hurt on YouTube.com. A genuinely funny and entertaining TED talk about a snake bite and pain neurology. No, really, you will actually laugh — it’s like stand-up comedy. A must-watch for anyone with chronic pain, and the professionals who care for them.
- Understanding Pain and what to do about it in less than five minutes on YouTube.com. Beautifully produced short video that neatly summarizes most of the key points in this article. I do have a few quibbles with the treatment advice provided, however (discussed in Mind Over Pain).
- Pain: The science and culture of why we hurt (book), by Marni Jackson. Amazon.com ❐ Marni Jackson’s book is the perfect book for thoughtful, liberal, middle-aged women in pain who will probably thoroughly enjoy Jackon’s style. Others may find it frustrating, overtly poetical and coquettish, neither rigorous enough for the science-minded, nor explanatory enough for the layperson seeking real understanding of either “the science or the culture of why we hurt.” Nevertheless, it is one of the most accessible and modern surveys of pain science available to readers.
- All in My Head: An epic quest to cure an unrelenting, totally unreasonable, and only slightly enlightening headache (book), by Paula Kamen. Amazon.com ❐ Like PainScience.com, this book offers an unusual combination of both humour and information about pain. Kamen is a completely engaging writer, and tells her story with both journalist rigour and personality.
- The Pain Chronicles: Cures, myths, mysteries, prayers, diaries, brain scan, healing & the science of suffering (book), by Melanie Thernstrom. Amazon.com ❐ Nicely summarized by Dr. Harriet Hall for ScienceBasedMedicine.org: “Melanie Thernstrom has written a superb book based on a historical, philosophical, and scientific review of pain. Herself a victim of chronic pain, she brings a personal perspective to the subject and also includes informative vignettes of doctors and patients she encountered at the many pain clinics she visited in her investigations. She shows that medical treatment of pain is suboptimal because most doctors have not yet incorporated recent scientific discoveries into their thinking, discoveries indicating that chronic pain is a disease in its own right, a state of pathological pain sensitivity.”
- A particularly excellent scientific paper by Lorimer Mosely: “Reconceptualising pain according to modern pain science”
- “Central sensitization: Implications for the diagnosis and treatment of pain,” Clifford J Woolf, Pain, 2010. Pain itself often modifies the way the central nervous system works, so that a patient actually becomes more sensitive and gets more pain with less provocation. That sensitization is called “central sensitization” because it involves changes in the central nervous system (CNS) in particular — the brain and the spinal cord. Victims are not only more sensitive to things that should hurt, but also to ordinary touch and pressure as well. Their pain also “echoes,” fading more slowly than in other people. For a much more detailed summary of this paper, see Sensitization in Chronic Pain.
- Sensitive nervous system (book), by David Butler. Amazon.com ❐
- Explain Pain (book), by David Butler and Lorimer Moseley. Amazon.com ❐
- Painful yarns (book), by Lorimer Moseley. Amazon.com ❐
- The Challenge of Pain (book), by Ronald Melzack and Patrick Wall. Amazon.com ❐
- “Gate Control Theory of Pain for Manual Therapists and Patients,” Nick Ng, www.massagefitnessmag.com. A detailed and accessible primer on gate control theory, with plenty of history and perspective too.
Aug 4, 2021 — New section: No notes. Just a new chapter. [Updated section: Pain as conditioned behaviour.]
June — Focus!: Migrated a large portion of this article to a new page dedicated to the topic of Mind Over Pain. It was just getting out of hand, trying to cover both the weirdness of pain and it’s mind-over-pain implications all on one page.
June — New section: Third of three new or rebooted sections about pain chronification and the types of chronic pain. [Updated section: Two very important types of chronic pain… that don’t even have names to distinguish them.]
June — New section: Second of three new or rebooted sections about pain chronification and the types of chronic pain. This one particularly fills a gap I have known about for ages, and I’m delighted to finally fill it. [Updated section: What if the alarm isn’t false? Not all chronic pain is “weird”!]
June — New section: First of three new or rebooted sections about pain chronification and the types of chronic pain. [Updated section: The Chronic Zone: The dysfunctionality of some persistent pain.]
June — Upgrade: Added table of contents.
Archived updates — All updates, including 13 older updates, are listed on another page. ❐
This document has a complex editorial history, and the update log is a bit spotty and confused in places. Originally there was only one article, this one, which covered both the "pain is an opinion" paradigm and tackled the thorny mind-over-pain implications. In mid 2021, I split it up and created a new article dedicated to Mind Over Pain.
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- Melzack R, Katz J. Pain. Wiley Interdisciplinary Reviews: Cognitive Science. 2013;4(1):1–15. PainSci #54582 ❐
This is the first of many generally relevant citations in this article. The authors, fellow Canadians Drs. Ronald Melzack and Joel Katz, have a long history of interesting research and clear writing on this topic. This is their short, technical version of the Big Idea of this article, namely that “pain is weird” and strongly “tuned”:
Pain is a personal, subjective experience influenced by cultural learning, the meaning of the situation, attention, and other psychological variables. Pain processes do not begin with the stimulation of receptors. Rather, injury or disease produces neural signals that enter an active nervous system that (in the adult organism) is the substrate of past experience, culture, and a host of other environmental and personal factors. These brain processes actively participate in the selection, abstraction, and synthesis of information from the total sensory input. Pain is not simply the end product of a linear sensory transmission system; it is a dynamic process that involves continuous interactions among complex ascending and descending systems.
- Modern pain research was kicked off in the late sixties by the work of Dr. Ronald Melzack and Dr. Patrick Wall.
- All the dumbed-down pain science in this article is presented in a more scholarly form by the erudite Lorimer Moseley, an Australian pain scientist, in his excellent article “Reconceptualising pain according to modern pain science”. Dr. Moseley’s article is a perfect companion to this one: a more in-depth tour of the science, but far more accessible than a neurology textbook.
- The most common kind of presumed cause of musculoskeletal pain — a “structural” or biomechanical problem, like a slipped disc, or a short leg — is one of the least likely actual explanations. The failure of such explanations for pain to pan out over the last 20-30 years is also evidence that there’s more to pain than just screwed up tissue. See Your Back Is Not Out of Alignment.
- Brodie EE, Whyte A, Niven CA. Analgesia through the looking-glass? A randomized controlled trial investigating the effect of viewing a 'virtual' limb upon phantom limb pain, sensation and movement. Eur J Pain. 2007 May;11(4):428–36. PubMed #16857400 ❐
- Moseley L, Gallace A, Spence C. Is mirror therapy all it is cracked up to be? Current evidence and future directions. Pain. 2008 Aug;138(1):7–10. PubMed #18621484 ❐
Despite widespread support of mirror therapy for pain relief in the peer-reviewed, clinical and popular literature, the overwhelming majority of positive data comes from anecdotal reports, which constitute weak evidence at best. Only two well described and robust trials of mirror therapy in isolation exist, on the basis of which we conclude that mirror therapy per se, is probably no better than motor imagery for immediate pain relief, although it is arguably more interesting and might be helpful if used regularly over an extended period. Three high quality trials indicate positive results for a motor imagery program that incorporates mirror therapy, but the role of mirror therapy in the overall effects is not known. Obviously, more robust clinical trials and experimental investigations are still required. In the meantime, the relative dominance of visual input over somatosensory input suggests that mirrors might have utility in pain management and rehabilitation via multisensory interactions. Indeed, mirrors may still have their place in pain practice, but we should be open-minded as to exactly how.
- Fisher JP, Hassan DT, O’Connor N. Minerva. BMJ. 1995 Jan 7;310(70).
This source is tough for readers to confirm. It’s widely cited, downright popular, because it’s a great anecdote, but of course that doesn’t mean much. Is it for real? It is indeed. If you are determined, you can verify the citation with a free trial membership for BMJ.com: the story is just one item in the full text of the “Minerva” column, which is a compilation of snippets of interest.
“Nocebo” is roughly the opposite of placebo: harm powered by belief, instead of relief.
Latin for “I shall harm” (which I think would make a great supervillain slogan). It refers to the harmful effect of … nothing but the belief in or fear of a harmful effect. Give someone a sugar pill and then convince them you actually just fed them a deadly poison, and you will probably witness a robust nocebo effect. A common funny-if-it’s-not-you nocebo in general medicine is the terror of “beets in the toilet”: people eat beets, and then think there’s blood in the toilet, and call 911. Nocebo is a real thing, and not to be messed with. It is one of the chief hazards of excessive X-raying and MRI scanning, for instance: showing people hard evidence of problems that often aren’t actually a problem.And that is one of the main reasons it can be valuable to learn about all this.
- Parr JJ, Borsa PA, Fillingim RB, et al. Pain-related fear and catastrophizing predict pain intensity and disability independently using an induced muscle injury model. J Pain. 2012 Apr;13(4):370–8. PubMed #22424914 ❐ PainSci #54315 ❐
The fear of pain was assessed in 126 brave volunteers with a questionnaire before — yikes — “inducing muscle injury to the shoulder.” (Don’t worry, nothing too awful for the subjects: they just did a workout with a lot of eccentric contraction that made them super sore.) The results were not what the researchers expected. This study is interesting because it found evidence that fear of pain before injury can predict recovery time. In other words: how well you respond to injury and recover is affected enough by fear that it can actually be predicted by measuring fear beforehand. That’s profound!
- Melzack R, Wall PD. Pain mechanisms: a new theory. Science. 1965 Nov;150(3699):971–9. PubMed #5320816 ❐
This is Melzack and Wall’s seminal paper arguing that (emphasis mine) “pain perception and response is triggered after the cutaneous sensory input has been modulated by both sensory feedback mechanisms and the influences of the central nervous system. We propose that the abstraction of information at the first synapse may mark only the beginning of a continuing selection and filtering of the input.” Among other things, this is the paper that described the mechanism of gate control and ultimately gave rise to the highly influential concept of the neuromatrix (Melzack).
- See Gawande: “New scientific understanding of perception has emerged in the past few decades, and it has overturned classical, centuries-long beliefs about how our brains work—though it has apparently not penetrated the medical world yet. The old understanding of perception is what neuroscientists call “the naïve view,” and it is the view that most people, in or out of medicine, still have. We’re inclined to think that people normally perceive things in the world directly. We believe that the hardness of a rock, the coldness of an ice cube, the itchiness of a sweater are picked up by our nerve endings, transmitted through the spinal cord like a message through a wire, and decoded by the brain.”
- See Sensation on a Small Scale.
- Beecher HK. Relationship of significance of wound to pain experienced. JAMA. 1956 Aug;161(17):1609–1613. PubMed #13345630 ❐
- Jackson M. Pain: The science and culture of why we hurt. Trade paperback ed. Random House; 2003.
See also: every paper written about pain neurology in the last 20 years.
- Nilakantan A, Younger J, Aron A, Mackey S. Preoccupation in an early-romantic relationship predicts experimental pain relief. Pain Med. 2014 Jun;15(6):947–53. PubMed #24716721 ❐ PainSci #52835 ❐
- Goldstein P, Weissman-Fogel I, Shamay-Tsoory SG. The role of touch in regulating inter-partner physiological coupling during empathy for pain. Sci Rep. 2017 Jun;7(1):3252. PubMed #28607375 ❐ PainSci #53159 ❐
- Moseley GL, Parsons TJ, Spence C. Visual distortion of a limb modulates the pain and swelling evoked by movement. Curr Biol. 2008 Nov;18(22):R1047–8. PubMed #19036329 ❐
The feeling that our body is ours, and is constantly there, is a fundamental aspect of self-awareness. Although it is often taken for granted, our physical self-awareness, or body image, is disrupted in many clinical conditions. One common disturbance of body image, in which one limb feels bigger than it really is, can also be induced in healthy volunteers by using local anaesthesia or cutaneous stimulation. Here we report that, in patients with chronic hand pain, magnifying their view of their own limb during movement significantly increases the pain and swelling evoked by movement. By contrast, minifying their view of the limb significantly decreases the pain and swelling evoked by movement. These results show a top-down effect of body image on body tissues, thus demonstrating that the link between body image and the tissues is bi-directional.
- That’s creative problem solving, but I think it only makes the impracticality point stronger: the very narrow field of view of binocs probably undermines the illusion significantly. Seeing an exaggeratedly remote looking arm through a peephole may not have the same effect. Not that it isn’t worth trying, but for this to work the brain must actually be fooled.
- Stanton TR, Gilpin HR, Edwards L, Moseley GL, Newport R. Illusory resizing of the painful knee is analgesic in symptomatic knee osteoarthritis. PeerJ. 2018;6:e5206. PubMed #30038863 ❐ PainSci #53038 ❐
- Höfle M, Hauck M, Engel AK, Senkowski D. Viewing a needle pricking a hand that you perceive as yours enhances unpleasantness of pain. Pain. 2012 May;153(5):1074–81. PubMed #22520059 ❐
- Pain itself often modifies the way the central nervous system works, so that a patient actually becomes more sensitive and gets more pain with less provocation. This is called “central sensitization.” (And there’s peripheral sensitization too.) Sensitized patients are not only more sensitive to things that should hurt, but also to ordinary touch and pressure as well. Their pain also “echoes,” fading more slowly than in other people. See Sensitization in Chronic Pain: Pain itself can change how pain works, resulting in more pain with less provocation.
- It’s not academic hair-splitting. It doesn’t mean that pain isn’t real, or that tissues can’t genuinely be in trouble. What it means is that all pain — always, no matter what — is an unreliable interpretation of information coming to your brain from your body. Just like your brain “constructs” the reality that you see and hear and touch, it also constructs the experience of pain.
- TheConversation.com [Internet]. Moseley L. Pain really is in the mind, but not in the way you think; 2013 Jul 20 [cited 14 Jan 6].
- I’m understating that, because I don’t want to blow too many minds. The idea that there might be little or nothing that anyone can do to “repair” tissue in any meaningful sense is a radical concept for a lot of professionals. I suspect there are a handful of possible examples, but the point is that almost all forms of manual and physical therapy, most of the time (whether we know it or not) are almost exclusively inputs to the nervous system. And “results” are the CNS responding with a new story. The tissue state remains the same, or only trivially changed. Flesh is remarkably good at staying just the way it is. (With a gradual, inexorable drift back towards homeostasis after injury.)
- Moseley GL, Butler DS. Fifteen Years of Explaining Pain: The Past, Present, and Future. J Pain. 2015 Jun. PubMed #26051220 ❐
A cogent formal summary and update on how this “explain pain” thing is going so far (pretty well). Moseley and Butler are always quite readable, even when writing for journals (imagine), but see also their blogging about the same thing.
- This misconception comes straight from some overzealous advocates of Explain Pain, who often vigorously promote the idea that pain is actually “unrelated” to tissue damage, or does not “correlate” with it “at all” — perhaps too vigorously. I have often seen claims that exaggerated. It’s true and important that the correlation between tissue damage and pain is often poor, but it is still clearly quite strong for most people most of the time.
- The central message of explaining pain is that pain often exaggerates the danger that tissue is in. In the phenomenon of “central sensitization,” the exaggeration is pathological and entrenched: danger signalling is consistently and severely exaggerated. But that’s an extraordinary situation. Pain is also routinely out of proportion to the danger even when there is absolutely no pathological sensitization going on at all, thanks solely to the brain’s power to modulate pain.