The causes of fibromyalgia remain unclear, but research points to changes in how the nervous system processes pain signals

Fibromyalgia does not stem from a single cause the way a broken bone or infection does. Instead, it appears to develop when several factors combine—genetic predisposition, physical or emotional stress, infections, or injuries—to alter how your central nervous system handles pain. The result is that your brain and spinal cord amplify pain signals, making ordinary sensations feel severe. This is why fibromyalgia pain is real and measurable, even though imaging tests like X-rays or MRIs typically look normal.

The shift in how pain is processed happens gradually in most people. You might notice symptoms beginning after a car accident, surgery, or a period of intense stress. In other cases, the onset is gradual with no clear trigger. Either way, the underlying mechanism is the same: your nervous system has become sensitized to pain.

Key Takeaways

  • Fibromyalgia involves amplified pain signaling in the central nervous system rather than damage to muscles, joints, or organs.
  • Genetic factors make some people more vulnerable, but a triggering event—such as infection, injury, or prolonged stress—often precedes symptom onset.
  • Abnormal levels of neurotransmitters like serotonin, norepinephrine, and substance P play a role in how pain signals are processed.
  • Sleep disruption, physical deconditioning, and psychological stress can both contribute to fibromyalgia development and worsen existing symptoms.
  • Research continues to evolve, and no single test can diagnose fibromyalgia, which is why doctors rely on symptom patterns and ruling out other conditions.

How nervous system sensitization creates widespread pain

In fibromyalgia, the nervous system becomes sensitized—meaning it responds to stimuli that would not normally cause pain, or responds with disproportionate intensity. This happens through a process called central sensitization, where the brain and spinal cord amplify incoming pain signals. A light touch, a temperature change, or mild pressure can trigger pain responses that feel severe.

Researchers have documented this using specialized imaging and testing. Positron emission tomography (PET) scans show that people with fibromyalgia have increased blood flow in pain-processing regions of the brain. Quantitative sensory testing—where researchers apply controlled pressure or temperature to the skin—reveals that fibromyalgia patients perceive pain at lower thresholds than people without the condition. This is not psychological; it is a measurable difference in how the nervous system functions.

The sensitization process likely involves a feedback loop. Chronic pain signals from an injury or illness can trigger changes in the spinal cord and brain that persist even after the original injury heals. Over time, the nervous system becomes "stuck" in a heightened state of alert, interpreting normal sensations as threats.

Genetic factors and family history

Fibromyalgia runs in families, suggesting that genetic predisposition plays a role. If a parent or sibling has fibromyalgia, your risk is higher than the general population. However, genetics alone do not cause fibromyalgia—they appear to create vulnerability that requires a triggering event to manifest.

Researchers have identified variations in genes related to neurotransmitter regulation, particularly genes affecting serotonin and dopamine. These variations may make some people's nervous systems more prone to sensitization when exposed to stress, infection, or injury. Studies of identical twins show that even when both carry the same genetic variants, only one twin may develop fibromyalgia, confirming that environmental factors are essential to disease development.

This genetic component explains why fibromyalgia is more common in some families and why certain populations show higher prevalence rates. It does not mean you will inevitably develop fibromyalgia if a family member has it—only that your baseline risk is elevated compared to someone with no family history.

Physical and emotional stress as triggers

Many people report that fibromyalgia symptoms began after a significant stressor—a car accident, surgery, a serious infection, or a period of intense emotional strain. Prolonged psychological stress, grief, or trauma can activate the nervous system in ways that, over time, lead to sensitization. Physical trauma like whiplash or a fall can do the same.

The mechanism involves the body's stress response system. When you experience acute stress, your body releases cortisol and adrenaline to prepare for a threat. Normally, these hormones return to baseline once the threat passes. In some people, particularly those with genetic vulnerability, repeated or prolonged stress can dysregulate this system. The nervous system remains in a heightened state, and pain pathways become more reactive.

This is why fibromyalgia often develops after a specific event but can take weeks or months to become noticeable. The triggering event may have been months ago, but the nervous system changes accumulate gradually until symptoms cross a threshold and become apparent.

Infections and immune system involvement

Some fibromyalgia cases appear to follow infections, particularly viral infections like Epstein-Barr virus, cytomegalovirus, or parvovirus B19. People have also reported symptom onset after Lyme disease, though the relationship remains debated among researchers. The infection itself may resolve, but changes in immune function and nervous system signaling persist.

Research suggests that certain infections trigger an inflammatory response that, in genetically vulnerable people, does not fully resolve. Immune cells release molecules called cytokines that can activate pain-sensing neurons in the central nervous system. Additionally, some infections may directly damage nerve fibers or alter the balance of gut bacteria, which research increasingly shows influences pain perception and immune regulation.

Not everyone who has these infections develops fibromyalgia, which again points to the importance of underlying genetic or constitutional factors. The infection acts as a trigger in susceptible individuals rather than a direct cause.

Sleep disruption and its role in pain amplification

Poor sleep is both a symptom and a contributor to fibromyalgia. People with fibromyalgia often experience non-restorative sleep—they may sleep for eight hours but wake unrefreshed, as if they never slept at all. Sleep studies show that fibromyalgia patients have abnormal sleep architecture, with frequent arousals and reduced time in deep, restorative sleep stages.

Sleep deprivation amplifies pain perception. During deep sleep, the brain consolidates memories and regulates neurotransmitters involved in pain control, including serotonin and norepinephrine. When sleep is disrupted, these regulatory systems fail to function properly, leaving the nervous system more reactive to pain signals. This creates a vicious cycle: pain disrupts sleep, and poor sleep worsens pain sensitivity.

Whether sleep disruption is a primary cause of fibromyalgia or a consequence of nervous system sensitization remains unclear. Most likely, it is both—sleep problems may contribute to initial sensitization, and once fibromyalgia develops, the condition further disrupts sleep, perpetuating the cycle.

Neurotransmitter imbalances and pain regulation

Fibromyalgia involves abnormal levels of key neurotransmitters—chemical messengers that regulate pain, mood, and sleep. People with fibromyalgia typically have lower levels of serotonin and norepinephrine, both of which normally suppress pain signals. They also have elevated levels of substance P, a neurotransmitter that amplifies pain perception. Cerebrospinal fluid from fibromyalgia patients shows substance P levels two to three times higher than in people without the condition.

These imbalances affect how pain signals travel through the nervous system. Serotonin and norepinephrine activate inhibitory pathways that dampen pain signals before they reach the brain. When these neurotransmitters are depleted, pain signals pass through unchecked. Substance P, by contrast, enhances pain perception, so elevated levels mean pain signals are amplified at every step.

The cause of these neurotransmitter imbalances is not fully understood. They may result from genetic variations in neurotransmitter production or reuptake, from chronic stress exhausting the systems that produce these chemicals, or from the sensitization process itself. Medications that increase serotonin and norepinephrine—such as certain antidepressants—can reduce fibromyalgia pain, supporting the role of these neurotransmitters in the condition.

Physical deconditioning and reduced activity

Once fibromyalgia develops, reduced physical activity often follows. Pain makes movement difficult, so people naturally move less. Over time, this deconditioning—loss of muscle strength and cardiovascular fitness—can worsen pain sensitivity and fatigue. Muscles become weaker, joints stiffer, and the body's ability to regulate pain diminishes further.

Whether deconditioning is a cause or a consequence of fibromyalgia is unclear, but it likely works both ways. Prolonged inactivity can contribute to nervous system sensitization, and once sensitization occurs, pain prevents the activity needed to reverse it. This is why graded exercise—gradually increasing physical activity under professional guidance—is considered part of fibromyalgia management, though the approach must be carefully calibrated to avoid triggering symptom flares.

Frequently Asked Questions

Is fibromyalgia caused by depression or anxiety?

Fibromyalgia and mood disorders often occur together, but one does not cause the other. Both involve similar neurotransmitter imbalances and nervous system changes. Depression or anxiety may develop as a response to chronic pain, or all three conditions may stem from shared underlying vulnerabilities. Treating mood symptoms can help reduce pain, but fibromyalgia is a distinct neurological condition, not a psychiatric disorder.

Can fibromyalgia be caused by overwork or stress alone?

Stress can trigger fibromyalgia in genetically vulnerable people, but stress alone does not cause it in everyone. Many people experience intense stress without developing fibromyalgia. The condition requires both predisposition and a triggering factor—stress is one possible trigger, but not the sole cause.

Does fibromyalgia run in families?

Yes, fibromyalgia is more common in families with a history of the condition, suggesting genetic factors increase risk. However, having a family member with fibromyalgia does not mean you will develop it. Environmental triggers and other factors also play essential roles.

Can an injury or accident cause fibromyalgia?

Fibromyalgia symptoms often begin after physical trauma like a car accident or surgery, particularly in people with genetic vulnerability. The injury itself does not directly cause fibromyalgia, but the trauma and stress response may trigger nervous system sensitization in susceptible individuals.

Is fibromyalgia caused by inflammation?

Traditional inflammatory markers are typically normal in fibromyalgia, which is why it was once thought to be non-inflammatory. However, research now shows subtle immune activation and elevated inflammatory molecules in some fibromyalgia patients. The inflammation appears different from conditions like rheumatoid arthritis and may involve the nervous system more than joints or tissues.