Pain is a signal of vulnerability

Disclaimer: I am not a medical professional, and this is not medical advice. This post only states my beliefs as a result of my research on the topic. Full disclaimer here.

Introduction

Millions of people are affected by chronic pain. For some, an injury or a disease is the cause. For others, the pain originates from their mind.

This essay explains the rationale behind this behavior of our mind and explores some ways to cure this type of chronic pain.

The purpose of pain

Pain serves a purpose. When we twist our ankle, it becomes painful. This is good, as it makes us aware of the injury and ensures that we do not step on it before it has healed.

But pain is not a signal of damage

Many believe that pain is a signal of damage occurring somewhere in our body. This is incorrect: pain is a signal that we are vulnerable, that damage can occur to us in the future. Most times, we are vulnerable because of damage (as in the example of the twisted ankle), hence the confusion between pain as a signal of damage and pain as a signal of vulnerability. I will try to explain why pain is indeed linked to vulnerability, but not (necessarily) to damage.

Not all the time that there is damage in our body do we feel pain, and not all the time do we feel pain when there is damage in our body. However, every time that we feel pain, there is a potential for future damage (a vulnerability).

Here are some examples of cases in which our body has been damaged and yet, pain is not felt:

• There are numerous reports¹ of soldiers in World War I and II who lost a limb in an explosion and yet did not feel any pain. Why? Because the injury meant they would not have to fight anymore and would soon be sent home. They felt less vulnerable to death in a hospital bed with a severed limb than when they had to fight in the trenches. The future felt safe, or at least safer, so no need for excruciating pain anymore. As I will show later, the pain neurons in the affected limb still fire to signal pain, but the signal is probably suppressed by their brain. Now that the soldier is on a boat on the way home, it has no utility towards changing their behavior: they are now attended by doctors and on their way home.

• When participating in sports, it's possible to sustain a minor injury. Often, the pain isn't felt until after the physical activity has ceased. This is likely because sports often resemble activities like fighting or fleeing. In such situations, there's a much greater risk of bodily harm if one rests in the presence of an enemy or predator that could kill them, compared to stepping on a twisted ankle or continuing to use a sprained muscle. Consequently, using the injured body part is perceived as less dangerous than not using it, and no pain is felt (at least after the initial few seconds). The pain signal is suppressed.

Examples of cases in which we feel pain but there is no actual damage to the body:

• If your finger touches a hot pot, you will feel pain, even if the touch only lasted for an instant and your skin did not receive any actual damage. In this case, pain was not a signal that your skin got damaged (it didn’t), but a signal that your skin might get damaged if the behavior persists (i.e., your skin is vulnerable). Similarly, when exposed to extreme cold for a short amount of time, your skin will feel painful. It is not damaged yet, but it will be if the exposure continues. Pain is not a signal of current damage, but of future one.

• Science writer Erik Vance tells us an interesting story. Sitting in a lab, he was administered electrical discharges. When the screen in front of him would turn red, he would receive a stronger charge; when it would turn green, he would receive a lighter one. After following this pattern for a few minutes, the researchers changed the rule: all discharges would be strong ones. Erik, who was not aware of the change, still perceived little pain when the screen was green, even though the actual discharges were strong. His brain overrode reality with expectations (of imminent body damage). Expecto, ergo est.²

• Psychosomatic pain. A condition for the emergence of psychosomatic pain is a perceived condition of generalized vulnerability (and, by association, future physical damage). I will clarify this later in the chapter.

I can draw an example of psychosomatic pain from my personal experience. When I was 23, I noticed a fast-growing black mole on my right foot. I did not feel any pain, but I decided to visit a dermatologist anyway. After the examination, he told me that the mole could degenerate if left unchecked. We scheduled the removal for the following week. During the seven days between the dermatologist’s visit and the surgical operation, my foot ached. Of course, there was no good reason for my foot aching: I had no injury, and there is no way that a tiny mole, even if malignant, would be painful. However, there I was, feeling pain. Why? During the first visit, the dermatologist said that the mole could degenerate if not removed. My brain captured that information and inferred that my foot was vulnerable. To ensure that I would stay focused on the task of removing the mole, it made me feel pain. (How physiologically my brain managed to make me feel pain will be explained later.)

Damage does not have to be physical

Physical damage can predict further physical damage. For example, if our ankle is twisted, we are in a vulnerable situation. Stepping on our ankle might make the injury worse, and a twisted ankle is also a liability if we have to escape from a predator or fight an enemy. Physical damage is a sign of a vulnerability.

However, current physical damage is not the only predictor of future physical damage. Psychological damage, social damage, and lack of resources also predict future physical damage. When we are healthy but in a condition that might lead to future ill health, we are vulnerable.

Some examples:

• If I lack the resources I need for living (food, money, shelter, etc.), I am at a higher risk of physical deterioration.

• If I did something wrong which harmed other members of my community, I face the risk of being isolated and ultimately ostracized by my community (social damage). Alone, it is much harder to find the resources needed for living and the help or support in case of need: over time, physical deterioration might follow.

• If I am depressed (psychological damage), I am a less attractive mate and a worse friend. This might lead me to be left alone by my previous friends. As explained in the previous bullet point, if alone, I am more likely to face a shortage of resources and external support, which directly leads to a higher risk of physical damage or deterioration.

Therefore, it makes sense for my body and brain to consider a lack of resources, social damage, and psychological damage as a vulnerability and thus akin to a risk of physical damage. This risk of physical damage then manifests as pain. However, such vulnerability and pain are generalized: they are linked to our personal situation, but not to any specific part of the body. If our body does not have reasons to target a specific part of our body with pain, it manifests the generalized vulnerability as stress. In the next section I will explain this process.

Stress as generalized vulnerability

First, let me explain the purpose of stress. The feeling of vulnerability is used to trigger reactions and to find solutions to the root cause of the vulnerability (how this takes place in practice will be the topic of the next section). However, such reactions, like all actions and reactions initiated or mediated by our brain, must undergo motivational gating by the basal ganglia. If such reactions are repressed (they do not manage to overcome the motivational gating), no solution or damage mitigation plan is found, and the vulnerability remains unaddressed. What started as a clear signal of vulnerability is now a generalized signal of vulnerability. Our brain still knows that something is wrong, even if repression through motivational gating does not allow it to know exactly what is wrong. Nevertheless, something has to be done. The signal that something has to be done is stress.

Our brain is mostly an inference machine. The role of each neuron or group of neurons is to recognize a pattern in the inputs it receives. Such inputs are of three types: sensorial data (bottom-up), context (lateral), and expectations (top-down). Let’s see a (much simplified) example of how this works. Let’s say that a neuron’s job is to fire when it recognizes a dog. This means that it will fire if it recognizes sensorial input corresponding to four paws, a body of a certain size, fur, a head, and a tail. If the only sensorial input is a tail, it will generally not fire. It needs a minimum number of sensorial stimuli matching the pattern of what a dog looks like in order to fire. This minimum number is called the admissibility threshold. For example, it might fire when 4 of the 5 visual characteristics of a dog listed above are recognized. However, top-down expectations might reduce the amount of sensorial data needed for the neuron to fire. If I am at home and I own a dog, I expect to see it in the living room. If, through the kitchen door, I only see a tail, my neuron will fire: it is highly probable that that tail means that my dog is there. In other words, top-down expectations reduce the admissibility threshold and thus the amount of proof (sensorial stimuli) needed to conclude that what is expected is indeed there.

Now, enter stress. Stress is a state of general vulnerability: our brain knows that we are vulnerable, but this vulnerability is not associated with a specific body part and thus does not generate pain. However, because of the vulnerability, our brain has a higher expectation of feeling pain. This top-down expectation lowers the sensory threshold for experiencing pain. My hypothesis³ is that, because of this top-down expectation, our brain will be more likely to find admissible sensory signals that are precursors of pain. Let’s see an example: I do some work in the backyard. Usually, I would need to lift a very heavy load to damage my back. Let’s say that lifting 50 kg would cause my back to suffer damage (such as a herniated disc). At this point, I will suffer pain: a signal that I need to rest; otherwise, I will suffer worse injuries. Even after healing, my brain is likely to remember that lifting 50 kg might cause back damage. The next time I lift 50 kg, even if my back does not actually get injured, I am likely to feel pain: a signal that I’m vulnerable to damage. Now, let’s imagine that I am in a stressful period of my life. This time, the pain threshold will be lower (due to the stress). One of two phenomena is likely to occur:

1. Since the pain threshold is lower, the sensory signals sent by my back to my brain when I lift 40 kg are enough to cause pain. I might think that I am injured and have a herniated disc, even if my back does not actually have any.

2. A generalized vulnerability manifests as stress as long as it does not have any admissible location to manifest as bodily pain. Lifting the weight gives my brain an admissible location to feel the pain: my back. So, I feel pain there.

(In some cases of chronic pain, doctors recommend serotonin reuptake inhibitors. This is probably because a lack of serotonin signals a lack of resources, which is a condition of vulnerability and therefore causes the pain admissibility threshold to be lowered.)

You might feel skeptical: can our brain truly imagine pain? Why would it do that to itself? Let me show you some medical results that suggest it truly is like that.

John Sarno’s patients

In his books “The Mindbody Prescription” and “The Divided Mind”, Dr. John Sarno describes numerous cases of patients with psychogenic pain: pain engineered by our brain. Dr. Sarno would conduct an objective analysis to eliminate other diagnoses. Then, he would interview them and notice that they were very stressed. He would then tell them that their pain was psychogenic: it originated in their brain. They did not feel pain because something was wrong in the body, but because their brain was making them feel pain. Their brain, he would explain, was doing so in order to distract them from thinking about inadmissible thoughts about themselves, which were unconsciously generating guilt, shame, and other emotions that would all create stress (Author’s note: I do not agree on this very point – I will explain my theory later). In some patients, the pain vanished over the next 24 hours; others needed to attend a few group sessions in which such mechanics would be explained in more depth. The results were surprising: after having worked with Sarno, about 85% of his patients reported improvements in their condition, with 44% of them reporting little or no pain.⁴

How could the brain of his patients generate pain? Sarno hypothesized that the brain achieved this result by contracting some blood vessels and generating mild ischemia (deprivation of oxygen) in the target tissues. If you doubt the ability of the brain to alter the size of blood vessels, just think about how we blush after doing something embarrassing: our brain increases the diameter of the blood vessels in our cheeks.

Arthroscopic surgeries of the knee

Sham surgeries are fake interventions where the patient is transported into the operating room and anesthetized. However, the doctors do not perform any surgery – they merely make the patient believe they did. The results have been surprisingly positive: for example, sham surgeries for arthroscopic surgery of an osteoarthritic knee proved to be as effective as real ones.⁵ This means that at least some cases of knee pain are not caused by actual body damage, but by the perception of a state of vulnerability.

Herniated discs

In his book “The Mindbody Prescription”, Dr. John Sarno reports a study published in the journal Spine. Doctors made lumbar CT scans of a group of people without lower back pain: they found disc abnormalities, stenosis, and other aging changes in 50% of patients over 40 years old. Such abnormalities were not causing any pain. Contrast this with the common procedure when a patient tells a doctor he has been suffering from back pain. Often, a scan of his back is ordered; if an abnormality is found, such as a herniated disc, responsibility for the pain is attributed to it. Sometimes, surgeries are even recommended. However, if herniated discs are also present in painless patients, how can we be sure that they are the cause of the pain in patients with back pain? There is a chance, writes Dr. Sarno, that at least in some of the patients with chronic back pain, the herniated disc is not the cause of the pain (or it is the cause of its onset, but not of its persistence). In such cases, psychogenic pain would be the cause.

The sources of pain

There are three sources of pain:

• Nociceptive pain: This is the pain we generally refer to in common conversation. It is caused by external harmful factors that excite our nociceptors (the neurons responsible for detecting extreme heat, extreme cold, wounds, impacts, and so on). This type of localized pain causes a bottom-up inference of a localized vulnerability.

• Psychosomatic pain: This pain occurs when nothing is wrong with our body, and yet our brain infers from our present situation that we are generally vulnerable (e.g., to social isolation, lack of resources, etc.). This inference generates stress and a top-down expectation of pain, which is eventually manifested in the most admissible body location.

• Psychogenic pain: Technically, this is a concurrence of the two previous cases. However, I have listed it as a separate occurrence to highlight the specific process. As with psychosomatic pain, our brain expects a body part to manifest pain. Different from purely psychosomatic pain, this top-down expectation triggers some physiological processes (such as mild ischemia – a lack of oxygen delivered to muscles⁶) which in turn trigger nociceptive pain. In this case, there is something unusual with our body, but only because of signals originating from our brain, causing the unusual condition in our tissues. Some may be skeptical that our brain can indeed generate changes in our body that, in turn, provoke pain. But just consider how our cheeks turn red when we are embarrassed: our brain can very easily initiate such physiological processes. Some might be skeptical that our brain indeed can generate changes in our body which in turn provoke pain. But just think about how our cheeks turn red when we are embarrassed: our brain can very easily initiate such physiological processes.

Chronic pain

Many theories on chronic pain propose that its onset is triggered by an episode of extreme stress. I believe that this is partially true. My hypothesis is that stress is not the trigger of chronic pain, but the enabler. There would be little reason for pain to persist if the vulnerability (the stress) is gone. Rather, it makes a lot of sense that pain persists as long as the vulnerability is there, and that it goes away once the vulnerability is gone.

Placebos

Professor Nicholas Humphrey tells a story⁷ about placebos and hamsters. “Suppose a hamster is injected with bacteria, which makes it sick – but in one case, the hamster is in an artificial day/night cycle that suggests it’s summer; in the other case, it’s in a cycle that suggests it’s winter. If the hamster is tricked into thinking it is summer, it throws everything it has got against infection and recovers completely. If it flings to study its winter, then it just mounts a holding operation, as if it is waiting until it knows it’s safe to mount a full-scale response. […] In winter, we are conscious about deploying our immune resources. That’s why a cold lasts much longer in winter than it does in summer. […] Placebos work because they suggest to people that the picture is rosier than it truly is. […] Placebos give people fake information that it’s safe to cure them.”

The purpose of pain is to modify our behavior to reduce our exposure to the vulnerability causing the pain. This might include finding a solution (e.g., treating a wound), distancing ourselves from the potential source of harm (e.g., taking our finger away from a hot pot), and putting ourselves in a situation where it is safe to heal (e.g., staying in bed).

Healing is often a costly process. Knowing whether now is the time to address the root source of harm is an important ability. Our body has to commit resources (energy, nutrition, attention, time, antibodies, etc.) that would be better used elsewhere.

Here are some examples of situations where it is not a good idea to heal:

• A wolf bites my hand. Instead of treating the wound, I should try to scare off the animal and then seek medical attention.

• The harvest is late, and we are suffering from malnutrition. Instead of lying in bed to reduce energy consumption, we should work in the field to ensure we have the maximum number of vegetables once they are ready.

• I sprained a leg muscle during a long hike alone in the mountains. The optimal reaction is to move cautiously to reach home, where it will be safe to rest and heal.

Our brain evolved the ability to infer whether now is a good time to commit the resources required for healing, or to persist in our default behavior unmodified by pain. Many factors can influence this inference. In particular, stress (which is a signal of a generalized vulnerability) might suggest to our brain that now is not the time to heal, and that it is appropriate to feel pain is a signal that we are not safe yet, and a reaction is needed.

Placebos work by suggesting to us that we are safe. If we are safe, there is no longer a need to conserve resources for fleeing or addressing the external source of harm. Instead, we can now commit them to healing.

Behavioral placebos

In the previous paragraphs, I said that placebos are suggestions that we are safe and can commit resources to heal.

Placebos are permissions to heal.

There is a second definition of placebo, which is more interesting from a behavioral point of view: Placebos are permissions to change. They are narratives we can tell ourselves to justify a change in our behavior.

Here is a story to use as an example: Elbert always wanted to dress more elegantly, but he never did so because it “wouldn’t fit him.” He already had some suits in his wardrobe and liked to wear them during weddings and other formal events. However, he could not bring himself to wear them on any other occasion. He feared that others would ask questions such as, “Why did you start dressing elegantly?” and “Why didn’t you do it before?” These thoughts prevented him from dressing up for a long time. One day, he received permission to change: his wife gifted him a suit. Finally, he had a coherent narrative to justify wearing one on informal occasions. It would not be his choice: it would be his wife’s.

Comedians not only know a large number of funny jokes; they are also very good at giving us permission to laugh. Similarly, a lady might have different perceptions of a serenade, based on whether it is performed by a cool, handsome guy or by a shy and uncool one. In the former case, it is perceived as a romantic gesture; in the latter, as a creepy one.

Rory Sutherland said, “Trumpets and marching are bravery placebos.” Placebos allow us to be confident. (As a side note: if being confident is a good thing, why aren’t we all always confident? It is because being confident isn’t always a good thing. Often, it is a bad idea to be confident when there are no reasons to be confident. For example, it can lead to being perceived as arrogant, as a bully, and lead to shame and ostracization. This is why our brain had to evolve the ability to infer from the situation at hand when to be confident and when not to. Lack of confidence, like all bad feelings and emotions, has an overall beneficial purpose or is the necessary byproduct of something beneficial.)

Conclusion

Physical damage is only one of the causes of pain.

If you suffer from chronic pain with no clear physiological cause or with a physiological cause that doesn’t seem to heal, consider the possibility that your unconscious self might feel so threatened that it believes that pain is an appropriate reaction.

In that case, two approaches might be beneficial: placebos, and taking care of those sources of stress that are making your unconscious self feel vulnerable.

Note: this was an excerpt from the 2nd edition of my book, The Control Heuristic.

Footnotes:

Footnotes

1. As reported in Henry K Beecher’s studies. ↩

2. Some readers might still doubt our mind's ability to consider inferred stimuli equal to sensed stimuli. The paper “Pavlovian conditioning–induced hallucinations result from overweighting of perceptual priors” (Powers, Mathys, Corlett, 2017) reports that “Pairing a stimulus in one modality (vision) with a stimulus in another (sound) can lead to task-induced hallucinations in healthy individuals. After many trials, people eventually report perceiving a nonexistent stimulus contingent on the presence of the previously paired stimulus”. ↩

3. The next part of this sub-chapter on pain is based on the work of Dr. John Sarno. I personally quite agree with his theories regarding how psychogenic pain is generated and how to cure it. I think, however, that he missed part of the purpose of pain: it is not (only?) a distraction, but a signal of vulnerability (and thus, a desperate focus signal). I also think he failed to catch the similarity between stress and pain: they are two faces (generalized and localized) of the feeling of the same concept: vulnerability. ↩

4. John Sarno, “The Divided Mind”. ↩

5. Moseley JB, O’Malley K, Petersen NJ, Menke TJ, Brody BA, Kuykendall DH, Hollingsworth JC, Ashton CM, Wray NP (2002). “A controlled trial of arthroscopic surgery for osteoarthritis of the knee”. New England Journal of Medicine. ↩

6. Dr. Sarno named TMS (Tension Myositis Syndrome) the clinical condition whose symptom is psychogenic pain induced via mild muscle ischemia. ↩

7. In his edge.com piece dated 2011-05-12 ↩