Updated on January 14, 2026.
Scientists are not exactly sure what causes the widespread pain, fatigue, and other symptoms of fibromyalgia. It’s widely believed they may result from changes in the way the brain sends and receives pain signals. What causes these changes could be a combination of genetic mutations as well as environmental or neurological factors.
These underlying factors, however, are shared by some other health issues, which lead to symptoms that may even be confused with fibromyalgia. It’s not clear if one causes the other. But this could help explain why fibromyalgia often occurs or overlaps with the following conditions:
Irritable bowel syndrome (IBS)
Many people with fibromyalgia also experience symptoms of IBS, a chronic and painful gastrointestinal (GI) condition. IBS symptoms include abdominal cramps, bloating, gas, and diarrhea or constipation. But like fibromyalgia, which is not harmful to the joints or organs, IBS does not cause damage to the intestines.
So, what does a GI condition have in common with fibromyalgia? Both are pain disorders that are not related to structural problems with the bones, organs, or other tissues in the body. And most people with these conditions are women, have a notable stressor or life event that either triggered or worsen their symptoms, have trouble sleeping, and have unusual fatigue. Both IBS and fibromyalgia often improve with talk therapy and other lifestyle adjustments, and certain medications can help manage both conditions. This suggests that IBS and fibromyalgia may share some contributing factors or result from similar changes in the central nervous system. It’s also possible that an imbalance of gut bacteria may play a role in fibromyalgia, or that fibromyalgia may trigger some GI symptoms.
Temporomandibular joint disorder
The temporomandibular joint (TMJ) is a hinge that connects the jawbone to the skull. Certain disorders can cause pain in this joint and the muscles that control jaw movement. People who clench their teeth, chew gum frequently, or bite their nails can develop TMJ pain. TMJ pain or dysfunction is also common among those with fibromyalgia. Researchers aren’t sure why, but it may be that stress, which is often tied to fibromyalgia, can cause people to grind their teeth or clench their jaw, leading to TMJ pain. If you have TMJ pain, let your healthcare provider (HCP) or dentist know. Taking steps to manage stress, applying cold or heat, and wearing a mouth guard during sleep could help.
Migraines and tension headaches
Headaches and migraines are also common among those with fibromyalgia. It’s unclear if fibromyalgia triggers head pain or if it’s the other way around. One theory is that over time migraines may alter how the brain responds to pain, or cause hypersensitivity to pain, increasing the risk for fibromyalgia. People with migraines often experience sensitivity to light and sound, while those with fibromyalgia are also sensitive to touch.
Another theory is that the musculoskeletal pain from fibromyalgia may send painful impulses that trigger headaches. People with fibromyalgia may have stress or tense neck muscles, which can lead to tension headaches. Migraines and fibromyalgia are both linked to lower-than-normal levels of the brain chemicals serotonin and norepinephrine. And both conditions are often associated with anxiety and depression.
Chronic fatigue syndrome
Chronic fatigue syndrome (CFS) is another chronic and sometimes debilitating condition that leads to persistent fatigue, muscle and/or joint pain, and trouble sleeping. Like fibromyalgia, the exact cause of CFS is unclear but it has similar risk factors, including infection, genetics, changes in the immune system or gut bacteria, physical trauma and emotional stress. Women are also more likely to develop CFS than men. There are no specific tests for CFS or fibromyalgia. As a result, it may be difficult to tell the difference between the two conditions. Typically, fatigue is the most troubling symptom for those with CFS while chronic pain is the chief complaint among those with fibromyalgia. But many of the treatments for fibromyalgia fatigue also help ease symptoms of CFS.
Depression, anxiety, post-traumatic stress disorder (PTSD)
People with fibromyalgia are more than three times more likely to also have depression than those who do not have the condition. This is why screening for depression is very important among those diagnosed with fibromyalgia. What is the connection? Managing a chronic and painful condition can weigh heavily on people’s mood and emotional well-being. But it’s also possible that changes in the brain and nervous system related to fibromyalgia could also play a role in low mood or symptoms of depression.
Inflammatory and autoimmune conditions (rheumatoid arthritis, ankylosing spondylitis, lupus, Sjögren’s syndrome)
Fibromyalgia is more common among those with certain inflammatory or rheumatoid conditions as well as some autoimmune diseases, including rheumatoid arthritis (RA), ankylosing spondylitis, Sjögren’s syndrome, and lupus. These conditions share several symptoms and having one of them increases the risk for fibromyalgia—but they are different. Overactive immune cells in the central nervous system may play a role in fibromyalgia, but fibromyalgia is not an autoimmune disease. Other inflammatory conditions that are not autoimmune diseases, such as osteoarthritis (OA), are also linked to fibromyalgia. It could be that chronic pain from one of the conditions causes the nervous system to become hypersensitive or overreact to normal touch or pressure, interpreting it as pain. Genetics, certain environmental factors and triggering events, such as infection or trauma, may also play a role in fibromyalgia.
Sleep disorders (insomnia, obstructive sleep apnea, restless legs syndrome)
The connection between poor sleep and fibromyalgia is a two-way street. Chronic pain can make it harder to fall asleep and stay asleep. In turn, getting insufficient quality rest can intensify the perception of pain and irritability. Inactivity from fibromyalgia and certain medication used to treat the condition can lead to weight gain. In turn, this can increase the risk for obstructive sleep apnea (OSA), a sleep disorder that causes the airway to become blocked during sleep, triggering loud snoring and pauses in breathing. People with fibromyalgia are also more likely to develop restless leg syndrome (RLS), a condition that causes an uncomfortable sensation in the legs and very strong urge to move them typically at night or when lying down. RLS may be one of the reasons why fatigue is a common symptom of fibromyalgia. RLS may also be a side effect of certain medications used to manage fibromyalgia, such as certain antidepressants. But both fibromyalgia and RSL may involve a dopamine imbalance in the brain, affecting mood, movement, and motivation.
