Why does chronic pain exist?

Why does chronic pain exist?

Maybe you know someone who deals with chronic pain on a daily basis. This, according toSociety for the Study of Pain“An unpleasant sensory and emotional experience, associated with real or perceived tissue damage.” Pain is associated with negative feelings, such as low mood. What's more: when it becomes chronic, it can become physically and emotionally crippling. What is behind these cases? Is pain a more complex process than it seems?

Our view of pain has evolved over the years. Today we know that it is perceived through the detection of potentially harmful stimuli by specialized cells called Pain receptors. These neurons communicate with each other and transmit stimulus information to the spinal cord and from there to the cerebral cortex and other brain structures.

It is in the brain that the painful perception we experience when, for example, we prick our finger or suffer from indigestion is generated. At this moment, our brain, mainly through a neurochemical system known as endogenous opioids, initiates analgesic mechanisms to prevent the delivery of painful stimuli.

The search for resources for pain relief dates back to prehistoric times, when humans began collecting opium, which mimics the analgesic mechanisms in our brain by being able to interact with the opioid system.

What is pain?

Under normal circumstances, pain perception is very helpful. It allows us to identify potentially harmful stimuli, puts us on alert and shapes our behavior to avoid these threats. Throughout history, organisms that recognized these risks were more efficient at responding, surviving, and passing on their genes better. Therefore, pain perception represents an evolutionary advantage.

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But what if the pain persists, even after the pain is over? In this case, it ceases to be a symptom that helps us survive. Disorganization of its perception can turn it into chronic pain, which represents a stressful condition for the brain. An example of this is pain resulting from central sensitization, which is difficult to treat and increases the risk of developing associated disorders.

The hidden face of chronic pain

In developed countries, up to one in three people suffer from chronic pain, and 50% of them say it interferes with their daily lives. Associated with this condition, it is common to find sleep problems, drug addiction (opioids, for example) and other drugs (such as alcohol). Anxiety affects between 2 and 18% of the general population, while in people with chronic pain the number rises to between 6 and 40%.

Studies with mice Implemented by our research group It made it possible to investigate how anxious behaviors and lack of motivation to obtain rewards emerge after the experience of inflammatory pain. By the way, females are more likely to develop it.

The basis of these changes in pain response lies in neurobiological changes in the mesocorticolimbic system, a series of brain regions associated with motivation and emotional states. Among these areas, the ventral tegmental area and the nucleus accumbens stand out, whose connection consists of a nerve impulse that leads to the release of a molecule called dopamine, which is key to properly regulating the system and maintaining its reward and motivational functions.

Simplification: The release of sufficient dopamine in the nucleus accumbens results in stimulation that allows us to reinforce behaviors that are beneficial to our survival.

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But what does this have to do with chronic pain and its associated diseases? Frequently, and our group is focused on understanding this connection at the cellular and molecular level.

It is important to remember that chronic pain represents stress on the nervous system that causes changes in the connections between nerve cells. Cells in the cortical-limbic system are no exception: dopamine levels are lower in people with chronic pain, leading to lower mood. In addition, changes in the amygdala, an area associated with stress and anxiety, also affect dopamine levels in the nucleus accumbens.

Under these conditions, psychological disorders such as depression or anxiety are common, and there is an increased risk of resorting to drugs, such as alcohol or opioids, as “self-medication” to release more dopamine and restore low levels. Through pain.

Despite the difficulties that living with chronic pain can pose, there are currently options to improve the quality of life of people with it and reduce the likelihood of developing these comorbidities. Some of these treatments include Complete focus of mind Training attention and memory.

However, we still have much to learn about chronic pain and the way it relates to comorbidities through brain-level adaptations, so biomedical research on this topic remains critically important.

(This article was originally published on Conversation. You can read the original text here)

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