Fibromyalgia causes widespread pain throughout the body, along with deep fatigue, sleep problems, and cognitive difficulties. It affects up to 5% of the world’s population, with women making up the majority of diagnosed cases, though recent reviews suggest the actual gender gap may be narrower than once thought (roughly 4% of women and 2.4% of men). Symptoms must persist for at least three months before a diagnosis is made.
Widespread Pain That Moves and Shifts
The hallmark symptom is pain in multiple areas of the body at once. Doctors evaluate this using a checklist of 19 body regions, including the neck, shoulders, upper and lower back, chest, abdomen, hips, and both sides of the arms and legs. To meet diagnostic thresholds, you typically need pain in at least seven of those areas alongside moderate levels of other symptoms, or pain in three to six areas with more severe accompanying symptoms.
The pain doesn’t stay in one spot. It can migrate from your shoulders one week to your hips the next, and it often feels like a deep, steady ache rather than a sharp or localized injury. What makes fibromyalgia pain distinct is that it’s driven by the nervous system itself, not by damage in the muscles or joints where you feel it. The leading explanation is that the brain and spinal cord amplify pain signals, a process called central sensitization. Brain imaging shows that people with fibromyalgia have heightened activity in pain-processing regions compared to people without the condition. Their spinal fluid also contains elevated levels of excitatory chemical messengers that ramp up pain signaling. At the same time, the brain’s built-in pain-dampening system shows reduced connectivity, meaning the body’s natural “volume control” for pain is turned down.
Fatigue That Rest Doesn’t Fix
Fibromyalgia fatigue is nothing like ordinary tiredness. Patients describe it as “an inescapable feeling of profound physical tiredness,” “weakness in the muscles,” and “a ghastly sensation of being totally drained of every fiber of energy.” It is not proportional to the effort you’ve exerted, and crucially, it is not relieved by rest. You can sleep for ten hours and wake up feeling as though you haven’t slept at all.
This fatigue is closely tied to disrupted sleep. Sleep studies on fibromyalgia patients reveal a specific pattern: fast, alert-type brainwaves (alpha waves) intrude into the deep, restorative stages of sleep. The result is shallow, fragmented sleep with more frequent awakenings, less deep sleep, and less REM sleep. Over successive sleep cycles through the night, this disruption actually gets worse rather than better. The term “unrefreshing sleep” appears throughout fibromyalgia research because it captures what patients consistently report: the feeling that sleep simply doesn’t do its job.
Cognitive Difficulties and “Fibro Fog”
“Fibro fog” is the informal name for a cluster of cognitive symptoms that can be just as disabling as the pain. It includes memory impairment, reduced mental clarity, difficulty concentrating, and slower processing speed. Studies measuring cognitive performance in fibromyalgia patients have found large impairments in learning, memory, attention, and the speed at which the brain processes and responds to information. Moderate impairments show up in executive function (planning, organizing, and switching between tasks) and working memory (holding information in mind while using it).
Brain imaging supports what patients experience subjectively. During verbal fluency tasks, where you have to quickly generate words fitting a category, fibromyalgia patients show reduced activity in the frontal brain regions responsible for higher-level thinking. Their brains also take longer to react to stimuli, which shows up as delayed response times in lab testing. For daily life, this can look like losing your train of thought mid-sentence, struggling to find the right word, forgetting why you walked into a room, or finding it harder to follow conversations in noisy environments.
Heightened Sensitivity to Sound, Light, and Touch
The same nervous system amplification that drives fibromyalgia pain also affects how you process non-painful sensory input. Research using controlled sound exposure found that fibromyalgia patients needed significantly lower sound pressures to rate noise as mild, moderate, or intense compared to healthy controls. This wasn’t about preference or mood. Quantitative testing confirmed that their nervous systems genuinely respond more strongly to both painful stimuli (heat and pressure) and harmless stimuli like sound.
Many people with fibromyalgia report that bright or fluorescent lights feel overwhelming, certain smells become intolerable, and clothing textures or seams that never bothered them before become irritating. Temperature sensitivity is also common, with cold environments being a particularly frequent trigger. This generalized hypersensitivity reinforces the central sensitization model: the problem isn’t in the eyes, ears, or skin, but in how the brain processes incoming signals.
What Triggers Symptom Flares
Fibromyalgia symptoms fluctuate. You may have stretches of manageable days followed by flares where pain, fatigue, and fog intensify sharply. Several patterns in what triggers flares have been identified.
Stress is one of the most consistent triggers. Studies show that higher stress levels are associated with increased pain intensity and pain unpleasantness, and that stress can independently amplify the effect of other triggers. Physical overexertion, particularly pushing past your limits on a “good day,” commonly produces a delayed flare lasting one to several days afterward.
Weather plays a measurable role for many patients. Research tracking daily weather data alongside patient pain reports found that drops in barometric pressure and increases in humidity were both significantly associated with worsening pain. The combination of falling barometric pressure and colder temperatures was particularly linked to heightened pain. Interestingly, the study also found that barometric pressure changes independently increased stress levels in fibromyalgia patients, suggesting weather may worsen symptoms through two separate pathways: directly amplifying pain and simultaneously raising stress, which then amplifies pain further.
Overlapping Conditions
Fibromyalgia rarely appears in isolation. It commonly overlaps with other conditions that share features of central sensitization, including irritable bowel syndrome, chronic migraine, temporomandibular joint disorders (jaw pain), and chronic pelvic pain. Depression and anxiety are also highly prevalent, though they can be both a contributor to and a consequence of living with chronic pain and poor sleep. The fatigue, pain, unrefreshing sleep, cognitive dysfunction, and mood symptoms of fibromyalgia tend to reinforce each other in a cycle, which is why treatment approaches that address only one symptom in isolation are often incomplete.
How Fibromyalgia Is Diagnosed
There is no blood test or imaging scan that confirms fibromyalgia. Diagnosis is based on the pattern and duration of symptoms. The current approach uses two scoring tools: a Widespread Pain Index that maps pain across 19 body regions (scored 0 to 19) and a Symptom Severity Scale that rates fatigue, cognitive symptoms, and unrefreshing sleep (scored 0 to 12). You meet the criteria if your pain score is 7 or higher with a symptom severity score of 5 or more, or if your pain score is between 3 and 6 with a symptom severity score of 9 or more. In either case, the symptoms must have been present for at least three months.
Because many of these symptoms overlap with other conditions, such as thyroid disorders, autoimmune diseases, or sleep apnea, doctors typically run blood work and other tests to rule out alternative explanations before settling on a fibromyalgia diagnosis. The average time from symptom onset to diagnosis remains frustratingly long for many patients, partly because the symptoms are invisible and partly because they span so many different body systems that people often see multiple specialists before the pieces come together.