Why do we feel pain more at night?

How to sing in the song of the musical Outcastsbased on the novel by Victor Hugo, “tigers come out at night, their voices are soft as thunder” (“But tigers come at night and their voices are as quiet as thunder”). We were all miserable one night when we tossed and turned in bed, staring at the ceiling because of unbearable pain in our back (or tooth, ear, knee…). During the day he was there, and now he haunts us and bites us like a wild tiger. Q: Why do you feel pain more intensely at night? What does science say about this?

Let’s start from the beginning: what is pain?

We’ve all been ill at one time or another – many of us are sure at this very moment – so this is not a strange phenomenon for anyone. However, if we have to define it, it starts to complicate matters. After numerous changes over the years, the International Association for the Study of Pain (IASP) agreed in 2020 to define pain as “an unpleasant sensory and emotional experience associated with or similar to that associated with actual or potential tissue damage.”

Thus, there is currently an opinion that this is a sensual experience, that it has an unpleasant emotional component and is associated with (or resembles) what is felt during physical damage.

What is this for?

We tend to think of this feeling as something negative, since by definition it is an unpleasant experience. But a person is a complex and well-coordinated machine that rarely has functions that are “just like that”.

The purpose of pain is to warn us that something is wrong; it is a survival mechanism that helps protect us from dangers that could threaten our physical integrity. Simply put: it is the signaling system that our brain needs to tell us that we are in danger and that encourages us to be safe. And we hate to feel the need to avoid it.

However, this is not a reaction to a stimulus, as was thought in the time of Descartes (for example: I touch something hot, and the pain saves me from burning, because it makes me withdraw my hand). The modern concept understands it as a product of our brain: it is this organ that tells us where, how badly and in what way it hurts.

Of course, external stimuli (such as the heat we mentioned earlier) send a signal to the peripheral nerves that connect to the brain. Then he will process it and turn it into something else: the so-called nociception. But this is only part of the experience, as the notion of pain includes our cognitive and emotional interpretation of this nociceptive.

In short, pain is not always directly related to the amount of pain stimuli we receive, since it can be felt even in their absence. An extreme example is the phantom limb phenomenon: there are people whose brains cause very real pain in an amputated body part.

Control Gate Theory

So why does the feeling intensify at night when we Safely In our bed? How does it help survival?

The explanation has to do with our brain’s processing systems and the science of perception. Back in the 1960s, Roland Melzak and Patrick Wall proposed their Gate Control Theoryin which they proposed that there is a door in the spinal cord that allows or does not allow noxious stimuli to enter the brain.

In other words: there will be certain things that will make the door close and we will feel less pain, and others will make it open and we will feel it more intensely. An example is the mechanical act of rubbing the skin if we are hit: the sensation of friction competes with the sensation of pain and is felt less.

In the silence of the night, the voices of those same tigers are heard more, just like we remember some uncomfortable situation that we experienced during the day and almost forgot. There alone, in the dark, nothing distracts us and nothing helps to close the door: no images, no sounds, no interaction with others.

Worst moment, at 4 am

Since the 1960s, the science of pain has evolved with new theories, new methods, and new discoveries. For example, a study published in Brain Last September also points to circadian rhythms as a possible key factor in the nocturnal accentuation phenomenon.

Ines Dage and her collaborators conducted a new laboratory study in which they found that the most intense pain (in this case, experimentally induced) is felt at 4 o’clock in the morning. A possible explanation is a lack of sleep, as its effect has also been demonstrated, but in Daguet’s model, the weight of circadian rhythms was much greater. These changes may be related to the cyclical levels of hormones we have throughout the day, such as immune system and inflammation-related cortisol and melatonin.

Regardless, we must not forget that this is a pilot study in a lab setting where participants are not in their natural environment (sleeping in their bed) and receiving pain stimuli artificially (using a heat inducing machine).

Predator alerts

Researchers Hadas Nachman-Averbuch and Christopher D. King published a commentary on a previous study, noting that from an evolutionary point of view, we are more vulnerable to predators at night, since we sleep at this time. So it makes sense that the lower intensity of stimuli is enough to wake us up to potential danger.

In short, more research is needed to understand why we feel more pain at night, but it looks like our brains are still trying to protect us from being eaten by tigers (in this case, real ones) while we sleep.

Rocio de la Vega de Carranza, Ramon y Cajal Researcher (Psychology), University of Malaga

This article was originally published on The Conversation. Read the original.

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