Pain really is in the mind, but not in the way you think
Ever noticed a bruise that you have absolutely no recollection of getting? Rebecca Partington
Everybody hurts, but not everybody keeps hurting. The unlucky few who do end up on a downward spiral of economic, social and physical disadvantage.
While we dont know why some people dont recover from an acute episode of pain, we do know that its not because their injury was worse in the first place. We also know that its not because they have a personality problem. Finally, we do know that, on the whole, treatments for chronic pain are not particularly successful.
This sobering reality draws up some interesting reflections on pain itself. What is pain? Is it simply a symptom of tissue damage or is it something more complex? One way to approach this second question is to determine whether its possible to have one without the other tissue damage without pain or pain without tissue damage.
And you can answer that one yourself ever noticed a bruise that you have absolutely no recollection of getting? If you answered yes, then you have sustained tissue damage without pain. Ever taken a shower at the end of a long day in the sun and found the normally pleasantly warm water, painfully hot? Thats not the shower injuring you its just activating sensitised receptors in your skin.
Such questions and their answers are of great interest to pain scientists because they remind us that pain is not simply a measure of tissue damage.
What is pain?
The International Association for the Study of Pain defines pain as an experience. Pain is usually triggered by messages that are sent from the tissues of the body when those tissues are presented with something potentially dangerous.
The neurones that carry those messages are called nociceptors, or danger receptors. We call the system that detects and transmits noxious events nociception. Critically, nociception is neither sufficient nor necessary for pain. But most of the time, pain is associated with some nociception.
The exact amount or type of pain depends on many things. One way to understand this is to consider that 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.
How might all these things modulate pain? The favourite theory among pain scientists relies on the complexity of the human brain. We can think about pain as a conscious experience that emerges in response to activity in a particular network of brain cells that are spread across the brain. We can call the network a neurotag and we can call the brain cells that make up the neurotag member brain cells.
Schematic of cortical areas involved with pain processing and fMRI. Borsook D, Moulton EA, Schmidt KF, Becerra LR/Wikimedia CommonsEach of the member brain cells in the pain neurotag are also member brain cells of other neurotags. If we have the phrase slipped disc in our brain for instance, it has to be held by a network of brain cells (we can call this the slipped disc neurotag). And its highly likely that there are some brain cells that are members of both the slipped disc neurotag and the back pain neurotag. This means that if we activate the slipped disc neurotag, we slightly increase the likelihood of activating the back pain neurotag.
Using this model, thinking that we have a slipped disc has the potential to increase back pain. But what if this piece of knowledge we have stored is inaccurate, just like our notion of a slipped disc? A disc is so firmly attached to its vertebrae that it can never, ever slip. Despite this, we have the language, and the pictures to go with it, and both strongly suggest it can.
When the brain is using this inaccurate information to evaluate how much danger ones back is in, we can predict with confidence that, if all other things were equal, thinking you have a slipped disc and picturing one of those horrible clinical models of a slipped disc will increase your back pain.
This is where our understanding of pain itself becomes part of a vicious cycle. We know that as pain persists the nociception system becomes more sensitive. What this means is that the spinal cord sends danger messages to the brain at a rate that overestimates the true danger level.
This is a normal adaption to persistent firing of spinal nociceptors. Because pain is (wrongly) interpreted to be a measure of tissue damage, the brain has no option but to presume that the tissues are becoming more damaged. So when pain persists, we automatically assume that tissue damage persists.
On the basis of what we now know about the changing nervous system, this presumption is often wrong. The piece of knowledge thats turning up the pain neurotag is actually being reinforced by itself! I think it goes like this: more pain = more damage = more danger = more pain and so on and so forth.
The idea that an inaccurate understanding of chronic pain increases chronic pain begs the question what happens if we correct that inaccurate piece of knowledge?
Weve been researching the answer to this for over a decade, and heres some of what weve found:
(i) Pain and disability reduce, not by much and not very quickly but they do;
(ii) Activity-based treatments have better effects;
(iii) Flare-ups reduce in their frequency and magnitude;
(iv) Long-term outcomes of activity-based treatments are vast improvements.
Theres compelling evidence that reconceptualising pain according to its underlying biology is a good thing to do. But its not easy. Our research group is continually looking for better ways of doing this, and were not the only ones. The idea of explaining pain has taken off in pain management programs and outpatients departments the world over.
Clinicians need to rethink too
What we know about how pain works is not just relevant to how we teach it to patients, we need to base our clinical decisions on it. This means abandoning Rene Descartes famous model of 1654. His drawing depicts a man with his foot in the fire and a pain receptor activating an hydraulic system that rings a bell in his head. Of course no one believes we have hydraulics making this happen, but the idea of an electrical circuit turning on the pain centre is still at the heart of many clinical practices across professional and geographic boundaries.
The type of thinking captured in Descartes' model has led to some amazing advances in clinical medicine. But the evidence against it is now almost as compelling as that against the world being flat.
Of course, those sailors who never leave the harbour might hang on to the idea of a flat world. And, in the same way, there are probably clinicians who hang on to the idea of pain equalling tissue damage. I suspect they either dont see complex or chronic pain patients, or, when they do, they presume that those patients are somehow faulty or psychologically fragile, or, tragically, are lying.
Perhaps they can continue to practice without ever leaving the harbour. The problems I want to solve clearly exist on the open seas.
Provided by The Conversation
This story is published courtesy of the The Conversation (under Creative Commons-Attribution/No derivatives).
- Pain after car accidents: a pain in the neck or brain? Nov 03, 2011 | not rated yet | 0
- Back pain putting people off balance Nov 18, 2011 | not rated yet | 0
- Treatment of chronic low back pain can reverse abnormal brain activity and function May 17, 2011 | not rated yet | 0
- Painful periods increase sensitivity to pain throughout the month May 06, 2011 | not rated yet | 0
- Crossing your arms relieves pain May 20, 2011 | not rated yet | 0
- Motion perception revisited: High Phi effect challenges established motion perception assumptions Apr 23, 2013 | 3 / 5 (2) | 2
- Anything you can do I can do better: Neuromolecular foundations of the superiority illusion (Update) Apr 02, 2013 | 4.5 / 5 (11) | 5
- The visual system as economist: Neural resource allocation in visual adaptation Mar 30, 2013 | 5 / 5 (2) | 9
- Separate lives: Neuronal and organismal lifespans decoupled Mar 27, 2013 | 4.9 / 5 (8) | 0
- Sizing things up: The evolutionary neurobiology of scale invariance Feb 28, 2013 | 4.8 / 5 (10) | 14
Why is zone 1 in liver more prone to ischemic injury?
May 23, 2013 Hi, Is it because around central vein, there is only deoxygenated blood from the vein where as in the periphery there is hepatic artery. Also why...
How can there be villous adenoma in colon, if there are no villi there
May 22, 2013 As title suggest. Thanks :smile:
How can there be a term called "intestinal metaplasia" of stomach
May 21, 2013 Hello everyone, Ok Stomach's normal epithelium is simple columnar, now in intestinal type of adenocarcinoma of stomach it undergoes "intestinal...
Pressure-volume curve: Elastic Recoil Pressure don't make sense
May 18, 2013 From pressure-volume curve of the lung and chest wall (attached photo), I don't understand why would the elastic recoil pressure of the lung is...
If you became brain-dead, would you want them to pull the plug?
May 17, 2013 I'd want the rest of me to stay alive. Sure it's a lousy way to live but it beats being all-the-way dead. Maybe if I make it 20 years they'll...
MRI bill question
May 15, 2013 Dear PFers, The hospital gave us a $12k bill for one MRI (head with contrast). The people I talked to at the hospital tell me that they do not...
- More from Physics Forums - Medical Sciences
More news stories
By discovering the new mechanism by which estrogen suppresses lipid synthesis in the liver, UC Irvine endocrinologists have revealed a potential new approach toward treating certain liver diseases.
Medical research May 23, 2013 | 5 / 5 (1) | 0 |
Aortic arch pulse wave velocity, a measure of arterial stiffness, is a strong independent predictor of disease of the vessels that supply blood to the brain, according to a new study published in the June issue the journal ...
Medical research May 23, 2013 | not rated yet | 0
Since the discovery of Prontosil in 1932, sulfonamide antibiotics have been used to combat a wide spectrum of bacterial infections, from acne to chlamydia and pneumonia. However, their side effects can include serious neurological ...
Medical research May 23, 2013 | 3 / 5 (1) | 0 |
Scientists at the National Institutes of Health report they have discovered in mouse studies that a small molecule released in the spinal cord triggers a process that is later experienced in the brain as ...
Medical research May 23, 2013 | 5 / 5 (3) | 0 |
Spanish researchers have discovered that the daily clearance of neutrophils from the body stimulates the release of hematopoietic stem cells from the bone marrow into the bloodstream, according to a report published today ...
Medical research May 23, 2013 | 5 / 5 (2) | 0
Coenzyme Q10 decreases all cause mortality by half, according to the results of a multicentre randomised double blind trial presented today at Heart Failure 2013 congress. It is the first drug to improve heart failure mortality ...
7 hours ago | 5 / 5 (2) | 5
Heart failure accelerates the aging process and brings on early andropausal syndrome (AS), according to research presented today at the Heart Failure Congress 2013. AS, also referred to as male 'menopause', was four times ...
7 hours ago | not rated yet | 1
Mortality and length of stay are highest in heart failure patients admitted in January, on Friday, and overnight, according to research presented today at the Heart Failure Congress 2013. The analysis of nearly 1 million ...
7 hours ago | not rated yet | 0
(AP)—Department of Justice lawyers have again asked a federal appeals court in New York to delay lifting age restrictions and prescription requirements on an emergency contraceptive popularly known as the morning-after ...
7 hours ago | not rated yet | 0
Two mutations central to the development of infantile myofibromatosis (IM)—a disorder characterized by multiple tumors involving the skin, bone, and soft tissue—may provide new therapeutic targets, according to researchers ...
23 hours ago | 3 / 5 (2) | 0 |
Talking on a hands-free device while behind the wheel can lead to a sharp increase in errors that could imperil other drivers on the road, according to new research from the University of Alberta.
23 hours ago | not rated yet | 1