Understanding the pathophysiology of fibromyalgia

  • Central pain treatment
  • Defective blocking of pain signals
  • Change in opioid receptors
  • Increase in substance P
  • More activity in pain-sensitive areas of the brain
  • Lack of pain reduction with positive emotional images
  • The causes
  • Genoa
  • Environmental triggers
  • Other explanations
The human brain

We know that fibromyalgia (FM) causes chronic widespread muscle pain, but the “why” behind this pain is unknown. Even more confusing, while the pain is certainly there, the muscles of those with FM are normal, with no signs of inflammation or damage. Of course, pain without visible damage is difficult to understand and treat, which is why for many years fibromyalgia has been mistakenly viewed as a psychological illness.

Over the years, however, as researchers delved into the physiology of FM, they discovered that fibromyalgia is a chronic pain disorder characterized by central sensitization or modified pain treatment.

Modified “central” pain treatment

Central sensitization means that your central nervous system, which is made up of your brain and spinal cord, processes pain differently (in a more “sensitive” way). For example, people with FM interpret painful stimuli, such as heat or pressure, to be painful at lower levels than people without the condition. They also perceive these sensations as more painful (greater intensity) than those without FM.

There are several mechanisms to support this idea of ​​treating abnormal pain in fibromyalgia. Here are some examples:

Defective blocking of pain signals

In healthy people, once a painful stimulus is felt, the brain signals the release of endorphins (your “natural opioids” or “feel-good chemicals”), which block further transmission of health signals. pain. But in people with FM, this pain-relieving system is defective.

With this defective system, not only is there a lack of “pain-inhibiting” signals, but it is impossible to block repetitive non-painful sensory stimuli. For example, a healthy person would eliminate the persistent, painless tapping of a pencil on the hand, while a person with FM would continue to feel the tapping. This suggests an inability to filter irrelevant sensory information from the environment. 

Change in opioid receptors

Changes in the number of opioid receptors have been reported in people with FM, particularly a reduction in the number found in the brain. Your opioid receptors are the host sites where endorphins bind to. With this reduction, a person’s brain is less sensitive to endorphins, as well as opioid pain relievers like Vicodin (hydrocodone / paracetamol) and Percocet (oxycodone / acetaminophen).

Increase in substance P

People with FM have been found to have high levels of substance P in their cerebrospinal fluid (the clear fluid that bathes your spinal cord). Substance P is a chemical released when a painful stimulus is detected by your nerve cells. Specifically, substance P is involved in the pain threshold, which is when a sensation becomes painful. High levels of substance P might help explain why the pain threshold is low in people with fibromyalgia.

More activity in pain-sensitive areas of the brain

Sophisticated brain imaging tests, such as functional magnetic resonance (fMRI), show that in fibromyalgia, activity is greater than normal in areas of the brain that suffer from pain. This suggests that pain signals are bombarding the brain or that the brain is abnormally processing the body’s pain signals.

Lack of pain reduction with positive emotional images

A small study in the journal  Pain,  which included 16 people with fibromyalgia and 16 healthy participants, found that unlike healthy participants, participants with FM did not show reduction in pain when they were experiencing painful hand stimuli, in addition to looking at positive pictures. This suggests an abnormal link between the perception of pain and emotion.

Causes of modified pain treatment

Experts suspect fibromyalgia is an abnormal pain processing disorder and believe that an interaction between a person’s genes and one or more environmental exposures triggers central sensitization. It is therefore what promotes the development of FM and / or other “central” pain disorders such as migraines or irritable bowel syndrome.


In terms of genes, there is no “fibromyalgia gene” (or set of genes) to test yet, but scientists are working hard to find genes involved in pain treatment pathways linked to pain. fibromyalgia. This can eventually help experts create specific targeted treatments for FM.

Environmental triggers

It is not known what environmental exposures are linked to FM. It is possible that an infection, such as a viral disease or Lyme disease, or emotional or physical trauma is the cause of the development of FM in genetically susceptible people.

Other explanations

Keep in mind, while an altered ‘core’ process seems to be at the heart of fibromyalgia, other factors are believed to contribute to the pain of FM such as poor sleep quality, potential hormonal disturbances, and problems. peripheral pain, such as myofascial trigger points or osteoarthritis, that trigger or contribute to chronic pain.

A word from Verywell

If you (or a loved one) have fibromyalgia, rest assured that your physical pain and increased pain sensitivity is real. It is not in your mind, but rather a consequence of the way your central nervous system processes pain.

As experts continue to discover and understand the biology of fibromyalgia and how it develops, feel free to know that you are not alone. In addition, there are therapies available to soothe your pain and improve your quality of life. Do not suffer in silence. Reach out to people like you and your doctor.


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