Comorbid Conditions in Fibromyalgia and Chronic Fatigue Syndrome

When two or more distinct medical conditions occur in the same person, they are considered comorbid conditions—meaning they occur at the same time.

Fibromyalgia syndrome (FMS) and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) are generally considered distinct, yet overlapping—they are two different medical conditions, yet they share symptoms.

But FMS and ME/CFS also have a host of comorbid (co-occurring) conditions associated with them, including other pain conditions, sleep problems, major depression, nervous system disorders, and digestive problems. Menstrual problems may also occur.

Woman with headache
Arman Zhenikeyev / Getty Images

Pain Conditions

Many people with FMS and ME/CFS also have other chronic pain conditions that need to be diagnosed and properly treated. Often, successfully treating other sources of pain can help alleviate FMS and ME/CFS symptoms.

Myofascial Pain Syndrome

Myofascial pain syndrome (MPS, sometimes called “chronic myofascial pain”) is frequently confused with fibromyalgia, but they are different conditions. In MPS, muscles and connective tissues (which make up the fascia) develop what are called trigger points.

A trigger point is often a small, hard knot, about the size of a pea, that you may be able to feel under your skin. Sometimes the knot itself is painful, especially when you press on it, but it often causes pain in another area.

Chronic Headaches

Some researchers believe that people with chronic headaches, such as migraines, and those with FMS may share common defects in systems that regulate specific chemical messengers in the brain, such as serotonin and epinephrine (adrenaline).

Researchers have also found low levels of magnesium in both ME/CFS and migraine sufferers, and when chronic migraine sufferers don’t respond to usual therapies, healthcare providers often consider the possibility of a more generalized pain syndrome, such as FMS. Headaches frequently occur with ME/CFS as well.

Migraine symptoms include heightened sensitivity to light and sound, nausea, vision problems such as auras or tunnel vision, difficulty speaking, and intense pain that’s stronger on one side of the head.

Multiple Chemical Sensitivity

Multiple chemical sensitivity (MCS) causes similar symptoms to ME/CFS and FMS, but with the trigger being exposure to certain chemicals, such as those found in perfumes, adhesives, and cleaning products.

Because everyone is exposed to a huge variety of chemicals every day, it can be extremely difficult to identify which ones are causing the problem, or even that the problem is, in fact, MCS.

Gulf War Syndrome

Symptoms of Gulf War syndrome are strikingly similar to those of FMS and ME/CFS, including fatigue, musculoskeletal pain, and cognitive problems, and they have been shown to share a similar pathophysiological pathway. Also similar is that symptoms and their severities vary widely from person to person.

Sleep Disturbances

Sleep disturbances are considered a key clinical feature of FMS and can include insomnia, sleep apnea, and other sleep disorders. Sometimes, a sleep study reveals impaired stage 4 sleep.

People with ME/CFS, however, generally have no diagnosable sleep disorders—instead, they have what’s called “unrefreshing sleep.”

People with FMS can also have sleep-related movement disorders.

Restless Leg Syndrome

Restless leg syndrome (RLS) is a movement disorder that causes discomfort, unease, and weariness that gets worse when you rest and feels better when you move. It can keep you awake because it’s hard to get comfortable, and the movements can wake you up as well. RLS is not well understood.

Periodic Limb Movement Disorder

Periodic limb movement disorder (PLMD) is similar to RLS. People with PLMD involuntarily contract their leg muscles about every 30 seconds while they’re asleep. Even if this doesn’t wake you up completely, it can disrupt sleep both for you and for your sleeping partner.

Major Depression

As many as 34.8% of people with FMS are suffering from a mood disorder, specifically a type of depression. Those with more comorbidities will experience a higher risk of major depression.

Researchers have outlined that depression and FMS have a similar roots and may exist on a spectrum. Moreover, FMS, ME/CFS, and major depression share many overlapping symptoms, such as difficulty concentrating and fatigue.

Major depression is much more serious than the normal periods of sadness and despondency that can go along with chronic pain and fatigue. Symptoms of major depression include:

  • Daily depressed mood
  • Loss of interest in usually pleasurable activities and hobbies
  • Significant weight changes
  • Insomnia or excessive sleeping
  • Constant low energy
  • Feelings of worthless or inappropriate guilt
  • Inability to make decisions or concentrate
  • Thoughts of suicide

It’s crucial for people with signs of major depression to get professional help.

Possible Nervous System Disorders

Other symptoms that sometimes show up alongside FMS include:

  • Chest pain
  • Heart palpitations (irregular or forceful heartbeat)
  • Possible association with mitral valve prolapse (heart valves not closing properly)
  • A sudden drop in blood pressure 

Digestive and Menstrual Problems

While the link between FMS/ME/CFS and digestive problems isn’t well understood, one theory is that it’s because they’re all associated with serotonin.

Irritable Bowel Syndrome

People with irritable bowel syndrome (IBS) have alternating bouts of constipation and diarrhea, and have frequent abdominal pain. Other symptoms include nausea and vomiting, gas, bloating, and abdominal distention.

Many people with IBS don’t seek medical care, but it’s important to do so. IBS can lead to malnutrition or dehydration (brought about by avoiding food) and depression.

Interstitial Cystitis

Interstitial cystitis (IC) is caused by inflammation of the bladder wall. It can be painful and frequently is misdiagnosed as a urinary tract infection. Many patients have IC for 10 years before they’re diagnosed correctly.

Women are much more likely than men to develop IC. Symptoms include urinary frequency, urgency and discomfort; pain during intercourse; and pelvic pain.

Relief from IC is difficult as well, generally requiring a lot of trial and error before the right combination of therapies and lifestyle changes is found.

Premenstrual Syndrome/Primary Dysmenorrhea

Women with FMS or ME/CFS frequently report more problems with premenstrual syndrome (PMS) and dysmenorrhea (especially painful periods).

PMS symptoms can include:

  • Headaches
  • Abdominal cramps
  • Bloating and gas
  • Backaches
  • Swollen or tender breasts
  • Mood swings

Typically, PMS may occur during the week before a period. With dysmenorrhea, painful cramps kick in about the time your period starts and generally last one to three days. Cramps can be either sharp and intermittent or dull and achy.

Dysmenorrhea comes in two varieties: primary and secondary. Primary dysmenorrhea is the one that occurs alongside FMS and ME/CFS; it is not caused by any identifiable problems. Secondary dysmenorrhea can be caused by infection, ovarian cyst, or endometriosis.

If you have dysmenorrhea that starts after your teenage years, you should talk to your healthcare provider about testing for an underlying cause.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Adrienne Dellwo
Adrienne Dellwo is an experienced journalist who was diagnosed with fibromyalgia and has written extensively on the topic.