What causes fibromyalgia or CFS? 

The exact causes of fibromyalgia and chronic fatigue syndrome (ME/CFS) remain the subject of intensive medical research in the United Kingdom and globally. While a single, definitive cause has not yet been identified for either condition, the consensus among UK health professionals is that they are complex, multi-system disorders. Current evidence suggests that these conditions often arise from a combination of genetic predisposition, environmental triggers, and changes in how the central nervous system processes information. Understanding these potential causes is a vital step for patients in the UK to help them navigate their diagnosis and the various management strategies offered by the NHS. 

What We’ll Discuss in This Article 

• The leading theory of central sensitisation in chronic pain 

• The role of the immune system and post-viral triggers 

• How genetics and family history may influence risk 

• The impact of physical and emotional trauma as potential catalysts 

• Abnormalities in energy production at a cellular level 

• The connection between the gut-brain axis and chronic symptoms 

Central sensitisation and pain processing 

One of the most widely accepted theories for the cause of fibromyalgia is central sensitisation. This is a process where the central nervous system, comprising the brain and the spinal cord, becomes stuck in a state of high reactivity. In individuals with fibromyalgia, the way the body processes pain signals changes, effectively “turning up the volume” on sensory input. This means that sensations that would not be painful for most people are perceived as significant discomfort, and actual pain is felt much more intensely. 

This heightened sensitivity is thought to be linked to abnormalities in the levels of certain chemicals in the brain, known as neurotransmitters, which signal pain. Research indicates that people with fibromyalgia may have higher levels of “substance P,” a chemical that transmits pain, and lower levels of serotonin and norepinephrine, which help to dampen pain signals. The NHS describes fibromyalgia as a condition that affects the nervous system’s ability to regulate pain, leading to the characteristic widespread aches and tenderness. 

In ME/CFS, a similar process of sensitisation may occur, but it often extends beyond pain to include a heightened sensitivity to light, noise, and touch. This suggests that the brain’s filtering system is not functioning correctly, leading to the sensory overload and “brain fog” that many patients describe. While the mechanism is similar to fibromyalgia, the resulting disability in ME/CFS is more focused on the profound exhaustion and the body’s inability to recover from minor exertion. 

Post-viral triggers and immune dysfunction 

A significant number of people with ME/CFS can trace the onset of their symptoms back to a specific viral or bacterial infection. This is often referred to as post-viral fatigue syndrome. Common triggers identified in the UK include the Epstein-Barr virus (which causes glandular fever), certain types of flu, and, more recently, the virus responsible for COVID-19. It appears that in some individuals, the immune system does not “reset” properly after the initial infection has cleared, leading to a state of chronic low-level inflammation or immune overactivity. 

This immune dysfunction may explain many of the symptoms of ME/CFS, such as swollen lymph glands, sore throats, and a general feeling of being “permanently ill.” According to the NICE guidance on ME/CFS, the condition is a physical illness that involves multiple body systems, including the immune system. While the infection acts as the initial trigger, the ongoing symptoms are thought to be caused by the body’s continued, and often maladaptive, immune response rather than the presence of an active virus. 

In fibromyalgia, while post-viral onset is less common, some patients do report that their symptoms began after a severe illness. This suggests that any significant physiological stressor can potentially disrupt the nervous system’s balance, leading to the development of chronic pain and fatigue. The link between the immune system and the nervous system is a primary area of focus for researchers looking to develop more targeted treatments in the future. 

Genetics and family history 

There is strong evidence to suggest that both fibromyalgia and ME/CFS may have a genetic component. Many patients report having a close relative, such as a parent or sibling, who suffers from similar symptoms of chronic pain or exhaustion. This does not mean there is a single “fibromyalgia gene,” but rather that certain genetic variations may make some individuals more susceptible to developing these conditions when they are exposed to environmental triggers. 

Researchers have identified several genes that may be involved in the regulation of neurotransmitters and the immune response. If a person inherits a specific combination of these genes, their nervous system may be more prone to becoming sensitised, or their immune system may be less able to recover from a viral challenge. However, genetics alone is rarely the whole story; it usually takes a combination of “nature and nurture” for the condition to manifest. 

In the UK, family history is often discussed during the diagnostic process to help GPs understand a patient’s risk profile. While genetic testing is not currently used as a standard diagnostic tool for these conditions on the NHS, knowing that a relative is affected can provide important context for a clinical assessment. It also helps to validate the patient’s experience by showing that their symptoms may have a biological basis that runs in their family. 

Physical and emotional trauma 

For many individuals, the onset of fibromyalgia or ME/CFS is linked to a period of significant physical or emotional stress. This could be a major injury, such as a car accident, a complex surgical procedure, or a period of intense psychological trauma. These “stressors” can push the body’s stress-response system, known as the hypothalamic-pituitary-adrenal (HPA) axis, into a state of permanent dysfunction. 

The HPA axis is responsible for controlling the body’s reaction to stress by releasing hormones like cortisol. In people with chronic fatigue or fibromyalgia, this system may become exhausted or dysregulated, leading to “hypocortisolism,” where cortisol levels are too low. This can result in a lack of energy, poor sleep, and a reduced ability to handle any further stress. This biological link helps explain why emotional events can lead to such severe physical symptoms. 

The NHS acknowledges that emotional stress can trigger fibromyalgia or make existing symptoms significantly worse. This is not to say that the condition is “all in the mind,” but rather that the brain and body are intrinsically linked. When the brain’s stress centres are overwhelmed, it can lead to physical changes in how the rest of the body functions, including the perception of pain and the regulation of energy. 

Abnormalities in cellular energy production 

In recent years, research into ME/CFS has increasingly focused on the mitochondria, which are the “power plants” of the cells. Some studies suggest that in people with ME/CFS, the mitochondria are unable to produce energy efficiently. This may be due to problems with oxygen delivery to the cells or a breakdown in the chemical processes that convert food into energy. This cellular energy deficit would directly explain the profound fatigue and the specific symptom of post-exertional malaise. 

If the cells cannot produce energy on demand, even minor activities, like standing up or having a conversation, can deplete the body’s available resources, leading to a physical crash. This theory is currently being investigated by various UK research institutions. While it is not yet used to diagnose the condition in a clinical setting, it provides a compelling explanation for why “rest” does not solve the exhaustion associated with ME/CFS in the way it does for healthy individuals. 

In fibromyalgia, cellular energy issues may also play a role, particularly in the muscles. Some patients show evidence of reduced blood flow to muscle tissues, which can cause pain and stiffness. While the primary issue in fibromyalgia remains the central nervous system’s perception of pain, these peripheral cellular issues may contribute to the overall burden of the condition and the physical limitations that patients experience. 

Conclusion 

The causes of fibromyalgia and ME/CFS are likely a combination of several factors, including central sensitisation, immune system triggers, genetics, and cellular energy issues. While a single “smoking gun” cause remains elusive, the medical consensus in the UK views these as legitimate physical conditions driven by complex biological changes. By understanding these potential causes, patients can better work with their healthcare teams to manage their symptoms and find strategies that address the specific triggers relevant to their own lives. 

If you experience severe, sudden, or worsening symptoms, call 999 immediately. 

Authority Snapshot (E-E-A-T Block) 

This article provides an evidence-based overview of the suspected causes of fibromyalgia and ME/CFS within the context of the UK healthcare system. It was written by the MyPatientAdvice team and reviewed by Dr. Stefan Petrov to ensure the content is medically accurate and aligns with the latest NHS and NICE clinical guidance. The purpose of this information is to help patients understand the biological complexity of their symptoms.