Monday, April 10, 2017

Pain is a Warning Signal

This article is a recent addition to my Power of Belief series (an excerpt for Part III). It is a simplified explanation of what pain is and how pain signals 'work'. For those dealing with short term or chronic pain, or trying to learn more about pain in general, I hope you find it a useful overview.

What is Pain Sensation and Pain Perception?                          

Pain is a warning signal. Pain is an alert, which our body uses to warn us about danger and harm. Pain is a fast, unpleasant, intense message that grabs our attention and shouts, "Something is wrong!" These alerts are meant to be uncomfortable, even awful, because their purpose is so incredibly important. They are the quickest way for our body to tell us, 'you are being harmed'. And they are a powerful motivator to avoid potential danger.

Pain is a process. While pain feels instantaneous, it's actually just very fast. Our body alerts us to pain using multiple steps in a special alert system. This system aims to tell us about pain in a way that is (1) fast and (2) informative. To meet these goals, pain sends multiple alerts, which range from simple (immediate) to complex (less immediate). They also operate on different levels of consciousness, working consciously, subconsciously, and unconsciously (Young, 2005). Pain operates at these different levels and complexities for our benefit, in order to help our body and mind make better judgments for injuries and dangers (Flor et al., 1990).

Pain is a manifold message. Pain alerts work in tandem for most injuries. For example, our body often moves from a painful source, like fire, before we even feel it! Your body can process pain more quickly than your mind, so it uses that information to act fast. However, your mind will feel it soon. And that sharp pain of a fresh burn can help remind you to protect your new injury. Extended pain from a burn also helps to encourage keeping it clean and bandaged. For manageable and short-term injuries, pain signals can help you to take proper care and heal faster! Unfortunately, if the source of pain cannot be helped or healed, pain can become problematic and debilitating.

Pain can be helpful. While pain feels bad and is definitely something we wish to avoid, it ultimately functions to improve health, wellness, and lifespan. Pain is valuable, when it is functioning properly. Your body and mind both use pain to guide goals and actions. Pain gives immediate consequences for injury, to help prevent our bodies from getting hurt (or hurt worse), and it helps reduce loss of limb or bodily function (Chapman et al., 2008). As such a critical warning system, its alerts will be loud and the mind is attuned to sensing them. There is even research that supports that pain can intensify when we try to suppress it/resist it (Turner et al., 2002). Pain wants us to 'get' its signal.

Consider zombies in popular shows and fiction; zombies are often unconcerned with limbs getting injured or even falling off. Without pain, they can simply ignore these losses, and their mobility suffers for it. Without basic warnings, their bodies quickly fall apart.

While pain may seem a nuisance, its signals are extremely valuable for our well-being and survival (when properly functioning). How does the process work though, and why is it possible for it to 'go wrong'?

Pain has its uses: it warns us when something is harmful,
and it helps us take care of injuries while they heal

Step-by-Step Process of Pain
Research has shown us that there are multiple steps involved in the experience of pain, and that pain is not a simple ‘Injury --> Pain’ experience. The following is an attempt to simplify a complex (and fascinating!) topic. There are entire courses on pain sensation and perception, so please consider this as a sample introduction.

Simplified Summary of the Steps of Pain Signaling: Stubbing Your Toe

  1. Stub toe and 'activate' pain nerves
  2. Pain nerves send a 'pain alert' to the Spine
  3. The Spine receives the pain alert
  4. Spine sends the pain alert to the Brain
  5. Brain takes the alert and 'processes' it, to understand the pain
  6. Brain 'experiences' the Pain (ouch!) 

More Details: What happens when you stub your toe? 
When something painful like an injury happens, there are several pathways and junctions that our body uses to ‘inform’ us of that pain. Remember, pain is an alert system, so our bodies want to make sure we notice it. Nerves, the spine, and the brain, all work together to say 'something bad is happening!'. After all, pain's purpose is to call our attention to injury. So it needs to be a clear, strong signal! And because there are many paths and turns for these signals, there are also many opportunities for our bodies to 'adjust' how that pain signal is experienced.

Analogy: Sending a Birthday Gift
For an analogy, consider a day where you need to send a gift to your friend.

The Big Day
One morning, you receive a calendar reminder that it is your good friend's birthday. Oh no, you can't believe you forgot! You need to send her a gift right away, so you can then tell her 'happy birthday!' and how the package is in the mail ('What, you haven't gotten it yet? I can't believe it didn't already arrive!...'). For that to happen, you need to (1) get the birthday reminder, (2) go to the store to buy a gift, and (3) go to the post office, where you will wrap the gift, pack it into the box, and pay for your postage/ship it to your friend. Last, (4), your friend will receive the delivery.

Similarities to Pain Alert Steps
Pain signalling is a bit similar to sending the birthday gift for your friend. Comparing to the toe stubbing example:

  1. Calendar reminder: an injury starts the alert (like stubbing your toe)
  2. Driving to the store: the pain alert travels to the spine
  3. Buying the present: your spine routes the pain alert to your brain
  4. Driving to the Post Office: the pain alert travels to your brain
  5. Wrapping, packing, paying for, and sending the delivery: processing the pain alert in your brain (where your mind compiles the signals into an experience)
  6. Delivery: your brain 'gets' or 'experiences' the pain
Now, if you consider this scenario, all those steps are necessary to send the gift to your friend, but each step also gives an opportunity for those steps to change. Maybe you go to the hardware store to buy her a fancy drill, but you see a stupendous jigsaw that she would love. Or you get the drill, because you remember her saying she needed a pneumatic drill for her collection. Maybe you get lost between the store and the post office, and you take twice as long as normal to get there. Maybe you get distracted at the post office because they sell lots of different wrap for the gift. Maybe there is a long line. Every step is an opportunity for something to go 'differently'.

How this Works in Practice
How are these 'opportunities' and 'signals' present when you stub your toe?

When you stub your toe, the pain nerves in that toe are activated. How intensely the nerves are activated depends both on (a) the severity of injury (how hard did you hit that toe?) and (b) the sensitivity of my nerves (how easily do those nerves 'fire'?) (reviewed in: Moayedi & Davis, 2013). Those activated nerves send a signal to your spine, which then sends a signal for your brain. Again, the path between the toe and spine gives another opportunity for pain intensity to be affected (this moment in the spine is called the spinal gateway). When the brain finally receives the signal, it must be processed before we are fully aware of what has happened. It processes the intensity, location, and meaning of that pain. These steps are fairly automatic, but they are also affected by how the body and brain is 'set up' to receive pain alerts.

These Signal Steps all Work Together to 'Tell Us' that We are in Pain
While this is a very simplified version of events, it gives a rough idea of how an injury sends a pain alert signal to the brain, and explains how those steps can change the signal we consciously experience. All that signaling feels instant, but it is actually just very fast. In fact, certain areas of the body have setups called ‘reflex arcs’, where a signal causes an automatic movement, because otherwise it would take too long to 'reach' your brain (Hagbarth & Finer, 1963). Those important signal steps take time to send! Thankfully, with a 'reflex arc' a possibly injured body part will move from danger before the brain gets the message and can react (e.g., bumping your shin kicks out your leg). This allows the body to avoid the step-by-step process of pain perception and protect itself before you can think. 

Full Pain Warnings take Steps and Time
In full, conscious experiences of pain, the multiple points of pain signal transmission can create opportunities for the body and mind to alter the sensation of pain and the experience of pain (Wager et al., 2004, Hoffman et al., 2011). Meaning, each step of pain is a valuable opportunity for the signal to be modified. After all, pain is an important reminder about danger! Each indvidual's body and mind does its best to package that message meaningfully, so we can then make the most use of it (Diatchenko et al., 2004).

Pain signal additions and changes are affected by the set up that they run along. This means that the state of your body and mind affect the pain experience (most importantly, the endurance and intensity of your pain experience). And your beliefs and thoughts can actually allow your brain to 'prepare' that pain experience in less intense ways (to read more on this, check out my series, Power of Belief, Part III). This becomes especially critical when dealing with enduring, lasting, chronic pain.

These numbers are determined by a combination of mental and physical factors!

Pain is a Warning Signal
If there is anything to remember from all this, it's that pain is a warning signal. Pain is a message that our body sends to tell us 'something is wrong'. Pain tells us that something we are doing is harmful. 

For those of us dealing with chronic pain, it can be difficult to remember that pain has a very basic, useful, critical function. And it's easy to forget its value, when you are dealing with pain that won't stop. But it's important to consider how pain works, because many of the same mechanisms operate for chronic pain. The main difference is the duration of the pain and its intensity. This can be due to repeated injury (such as with IBD, endometriosis, and other inflammatory illnesses) and/or due to scarring and overactivation of nerves. It even involves changes in how the brain processes pain (Coderre & Melzack, 1985; Woolf & Salter, 2000). Different people develop chronic pain for different reasons (Michael & Burns, 2004; Kehlet et al., 2006; Blyth et al., 2007).  

Knowing how pain works can help us to understand how to reduce it, by both collaborative research and personal improvement. We have tools we can use to make pain better. We can work to help turn down the warning signal when it stops being useful. As well as give it appropriate respect for when it is being useful.

Reference List

  • Blyth, F. M., Macfarlane, G. J., & Nicholas, M. K. (2007). The contribution of psychosocial factors to the development of chronic pain: the key to better outcomes for patients?. Pain, 129(1-2), 8-11
  • Coderre, T. J., & Melzack, R. (1985). Increased pain sensitivity following heat injury involves a central mechanism. Behavioural brain research, 15(3), 259-262.
  • Diatchenko, L., Slade, G. D., Nackley, A. G., Bhalang, K., Sigurdsson, A., Belfer, I., ... & Max, M. B. (2004). Genetic basis for individual variations in pain perception and the development of a chronic pain condition. Human molecular genetics, 14(1), 135-143
  • Flor, H., Birbaumer, N., & Turk, D. C. (1990). The psychobiology of chronic pain. Advances in Behaviour Research and Therapy, 12(2), 47-84.
  • Hagbarth, K. E., & Finer, B. L. (1963). The plasticity of human withdrawal reflexes to noxious skin stimuli in lower limbs. Progress in brain research, 1, 65-81.
  • Hoffman, H. G., Chambers, G. T., Meyer, W. J., Arceneaux, L. L., Russell, W. J., Seibel, E. J., ... & Patterson, D. R. (2011). Virtual reality as an adjunctive non-pharmacologic analgesic for acute burn pain during medical procedures. Annals of Behavioral Medicine, 41(2), 183-191.
  • Kehlet, H., Jensen, T. S., & Woolf, C. J. (2006). Persistent postsurgical pain: risk factors and prevention. The Lancet, 367(9522), 1618-1625.
  • Michael, E. S., & Burns, J. W. (2004). Catastrophizing and pain sensitivity among chronic pain patients: moderating effects of sensory and affect focus. Annals of Behavioral Medicine, 27(3), 185-194.
  • Reviewed by: Moayedi, M., & Davis, K. D. (2013). Theories of pain: from specificity to gate control. Journal of neurophysiology, 109(1), 5-12.
  • Turner, J. A., Jensen, M. P., Warms, C. A., & Cardenas, D. D. (2002). Catastrophizing is associated with pain intensity, psychological distress, and pain-related disability among individuals with chronic pain after spinal cord injury. Pain, 98(1), 127-134.
  • Wager, T. D., Rilling, J. K., Smith, E. E., Sokolik, A., Casey, K. L., Davidson, R. J., ... & Cohen, J. D. (2004). Placebo-induced changes in FMRI in the anticipation and experience of pain. Science, 303(5661), 1162-1167.
  • Woolf, C. J., & Salter, M. W. (2000). Neuronal plasticity: increasing the gain in pain. science, 288(5472), 1765-1768.


  1. Replies
    1. Thank you Debbie! I hope you found it informative :). I still need to make a good info-graphic, to help make it clearer I think!


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