Almost everyone experiences pain. Around 50% of adults experience chronic pain. What is pain? How does pain work? Why do we need it? What happens if we don’t have it? What is the difference between acute and chronic pain? What is the difference between pain and suffering? What can we do to reduce pain and suffering?
Have you ever wished that you didn’t experience pain? Many people can relate to that idea. Be careful what you wish for. Some people have no pain through a rare condition (1 in 25,000, approximately). It renders them unable to feel pain.
Congenital insensitivity to pain (CIP), often referred to as congenital analgesia, sounds like a good idea until we learn that it dramatically impairs the lives of sufferers and is extremely and life-threateningly, dangerous.
Touching something dangerously hot causes pain. Thankfully! If we did not have pain, our chances of survival would be diminished. Pain educates us, tells us we have been injured or something is wrong, motivates us to remove harmful things from our lives, and, tells us to take time to heal. When it serves us, it keeps us healthy; it keeps us alive. We need pain.
How does the body sense pain, or indeed any other sensation? Surely, we can answer that simple question. How do we sense when something is wet, when we have no receptors for “wet”?
Although our skin has no such receptors, our brains unconsciously combine the signals associated with “wet” so that we can sense it. How does that process work?
Throughout most of our bodies, we have receptors and nerve endings, which are thought to detect pain and other sensations. Looking at pain specifically, the theory is that when triggered by potentially harmful stimuli, the nerve endings send a signal through specific nerve fibres to the spinal cord. Together the nerve and nerve endings are called the primary afferent nociceptors. From there the signal goes to “second order” pain transmission cells in the spinal cord, to be sent on to other systems, including the brain.
That all sounds rather certain and well-understood. There are four stages: transduction, transmission, pain modulation, and perception.
In the transduction phase, a stimulus (pain input) is detected by the nerve endings. Transmission is the sending process of the signal being sent via the nerves. Pain modulation is the process whereby the pain signals are altered along the way to being perceived.
Alas, we have very limited knowledge of how the stages work individually or together. Yes, we have theories, but not understanding. There are four main theories, and while each makes a contribution, none can fully
explain pain. I mention them here only in passing to enable you to explore further if you wish: Specificity Theory, Intensity Theory, Pattern Theory, and Gate Control Theory.
In whichever way we sense pain, it is, in large part, an unconscious process. In many parts of our bodies, we have much innervation; many pain receptors. Some body parts have more pain receptors than others, the eyes, for example. Some have none, for instance, the brain. The intestines have limited types of pain sensitivity.
There seems to be wide variation on how much pain each person feels in response to the same input. There is also considerable variation in the coping strategies that people use to deal with pain.
If you have been caused pain by say, banging your shin or by an insect bite, you may have noticed that you tend to rub the area around the injury site. Why? It seems that by stimulating the general area, you send signals to the brain which go some way to “drowning out” or “distracting” you from the injury’s pain signals. The perception of pain seems to be reduced, or displaced by such rubbing.
Displacement or distraction activities, for the purposes of drowning out pain, are very effective. Indeed, activity (mental or physical), generally is very useful at reducing or blocking pain.
In war after war there are always reports of people who have suffered the most horrendous injuries, but because they were so focused on something else, they had no awareness of the injury or pain.
Ask anyone experienced in the emergency services if they have seen such cases, and you will be hard-pressed to find someone who has not. Over and over again, there are examples of people being involved in, say, an
accident, who then go to help other people when in fact, their injuries were much more serious. The helper, distracted, feels no pain.
The mind seems to have some mechanism to either block the pain from entering consciousness or stops it at a stage before it even enters the brain, at non-conscious levels. Is there some kind of gateway? It appears that way. How does it work? That, alas we cannot answer with anything other than speculation.
Here is one piece of speculation. Pain is a useful signal if it warns us of harm. Pain is a harmful signal if it renders us unable to protect ourselves from further harm.
It seems reasonable to suggest this. In the course of evolution, some mechanism has evolved that enables us to feel pain when it is helpful and to block it out if feeling the pain would impair our chances of survival
while in a life-threatening situation. That would explain why some people in crisis situations have no pain from the most horrific injuries in an ongoing life-threatening situation.
Suggesting that there is such a mechanism is a long way from understanding what it is and how it works. We simply don’t know how the mind is able to block out pain when under extreme threat or why some people seem to experience this “crisis pain suppression effect” and others do not.
Some people have long-term conditions which are known to cause pain, yet they, seem to experience little if any, perception of pain. Why? Do they habituate to it?
Habituation is the process whereby the brain seems to pay less attention to an input that is constantly or regularly present. Do their brains filter it out and ignore it as not helpful? Some people seem better able to habituate to pain than others, and, as you may have guessed, we don’t know why. Neither do we know how the habituation process works.
Other people experience the pain that most patients report for any given identical injury, but they don’t seem to suffer from the pain. They have pain but not the usually associated emotional suffering. Why?
There are psychological and social elements to pain. For some people, an active choice is made, which can be expressed as: “The pain is real; suffering is a choice.”
Can some people choose how they handle the pain? Yes. Speak to any military commander and ask them to confirm or refute this: During training, can some people handle what ought to be vast amounts of pain and carry on effectively, and others can’t? Their answer will be a clear and unqualified yes.
The fact that the brain can turn off the sensation of pain in crisis situations, or by habituation, or by choice, tells us that our minds play a massive part in the perception of pain.
What is the difference between acute and chronic pain? Acute pain, to many people in the general population, is the pain that occurs at the point of an injury. Chronic pain is ongoing.
With more formal definitions, acute pain means any pain that lasts until the injury is healed. Even among pain management professionals, there is no agreement on when the pain ceases to be acute and when it becomes chronic. The time span ranges from 12 to 52 weeks.
That definition and distinction between acute and chronic breaks down when considering phantom limb pain (reflex sympathetic dystrophy – RSD). The injury site has healed, yet pain is felt in the absent limb in cases of RSD. Since the limb is no longer there, pain signals can’t be sent from it. Yet the brain genuinely feels pain. What is going on there?
Frankly, no one knows, but here is a likely hypothesis. The brain is constantly receiving signals from all parts of the body. How does the brain respond when no signals come from a major body part?
Should it ignore the absence of a signal? Or, in evolutionary survival terms, is it wise for the brain to alert consciousness to the problem? In other words, does the brain read “no signal” of any kind from a body part as a very serious signal? If so, that would explain RSD.
Can we test that hypothesis? We already have. People who suffer from RSD for two years or more are thought to be incurable. Chronic pain from RSD is widely thought to be one of those “live with and ameliorate it” conditions.
If the assumption is made that the brain is creating pain signals because of the absence of any input from the missing limb, what would happen if the brain received some input? What would happen if the missing limb was interpreted, by the brain, to be there still, and was able to carry out tasks? Would the brain sense that the limb was there and stop the pain?
In a series of experiments, people with RSD were asked to conduct tasks while looking in a mirror at the remaining limb so that it would appear, in the reflection, as the missing limb. What were the results?
Of those people who had RSD for less than three months, 100% were free of pain after the programme of exercises. Of those who had suffered RSD for more than two years, 50% were pain-free, and the remaining 50% had lower levels of pain. The treatment has been widely adopted and is known as mirror box therapy.
That shows dramatically that pain can be impacted by the way the brain processes the signals or the absence of signals. Now, what was previously thought to be incurable, RSD is fully treatable in the majority of cases.
Hyperalgesia is the name given to the sensation of pain that is much greater than would normally be associated with any given pain cause. Some people seem to experience pain at a much higher intensity than others. What explains that? We don’t really know.
Allodynia is pain coming from an event that would not normally cause pain. Again, we have little understanding of its causes. Idiopathic pain is the label given to pain when there is no discernible cause.
Medically unexplained symptoms, such as pain, may later be explained by some cause, which was undetected at the time it was medically unexplained. Where that is not the case, idiopathic pain is not understood.
Referred pain is the label given to pain physically coming from one location yet being experienced in another. Again, referred pain is not well understood, although it seems to, in some cases, follow predictable patterns. For example, if you put your elbow in a bucket of ice water, you will feel the pain in your hand.
What can we do to reduce pain and suffering? That is a question for the ages. In many cases, with modern medicines, physical pain can be removed or ameliorated with a wide range of painkillers. Where pain seems resistant to biochemical interventions, there are practical techniques that can be learned.
The psychological and social elements of pain management we are only beginning to understand. People who have great relationships, sound finances, and a strong sense of meaning, purpose and significance in their lives, seem to have a higher threshold for pain; they experience less pain for any given injury.
Whatever someone’s circumstances, there are useful pain management techniques which can be learned. In many countries, there are pain management clinics for people who have chronic pain, where the most effective methods and techniques can be adopted and practised.
Professor Nigel MacLennan runs the performance coaching practice PsyPerform.