Chronic fatigue syndrome (CFS) is a debilitating disorder characterized by extreme fatigue or tiredness that doesn’t go away with rest and can’t be explained by an underlying medical condition.

CFS can also be referred to as myalgic encephalomyelitis (ME) or systemic exertion intolerance disease (SEID).

The causes of CFS aren’t well understood. Some theories include viral infection, psychological stress, or a combination of factors.

Because no single cause has been identified, and because many other illnesses produce similar symptoms, CFS can be difficult to diagnose.

There are no tests for CFS, so your doctor will have to rule out other causes for your fatigue when figuring out a diagnosis.

While CFS has in the past been a controversial diagnosis, it’s now widely accepted as a medical condition.

CFS can affect anyone, though it’s most common among women in their 40s and 50s. There’s currently no cure, so treatment for CFS focuses on relieving symptoms.

Here’s what you need to know:

The cause of CFS is unknown. Researchers speculate that contributing factors may include:

It’s also possible that some people are genetically predisposed to develop CFS.

Though CFS can sometimes develop after a viral infection, no single type of infection has been found to cause CFS. Some viral infections that have been studied in relation to CFS include:

Infections caused by bacteria, including Coxiella burnetii and mycoplasma pneumoniae, have also been studied in relation to CFS.

The Centers for Disease Control and Prevention (CDC) have suggested that CFS may be the end stage of multiple different conditions, rather than one unique condition.

In fact, around 1 in 10 people with Epstein-Barr virus, Ross River virus, and Coxiella burnetii develop a condition that meets the criteria for a CFS diagnosis.

Additionally, they say that those who’ve had severe symptoms with any of these three infections are at a higher risk of later developing chronic fatigue syndrome.

People with CFS sometimes have weakened immune systems, but doctors don’t know whether this is enough to cause the disease.

People with CFS can also sometimes have abnormal hormone levels, but doctors haven’t yet concluded whether this is significant, either.

CFS is most commonly seen among people in their 40s and 50s.

Gender also plays an important role in CFS, as women are two to four times more likely to be diagnosed with CFS than men.

Genetic predisposition, allergies, stress, and environmental factors may also increase your risk.

The symptoms of CFS vary based on the individual affected and the severity of the condition.

The most common symptom is fatigue that’s severe enough to interfere with your daily activities. For CFS to be diagnosed, fatigue must last for at least six months and must not be curable with bed rest.

Additionally, you must have at least four other symptoms.

Other symptoms of CFS may include:

You may also experience extreme fatigue after physical or mental activities. This can last for more than 24 hours after the activity.

People are sometimes affected by CFS in cycles, with periods of feeling worse and then better again.

Symptoms may sometimes even disappear completely, which is referred to as remission. However, it’s still possible for them to come back again later, in a relapse.

The cycle of remission and relapse can make it difficult to manage your symptoms.

CFS is a very challenging condition to diagnose.

According to the Institute of Medicine, as of 2015, CFS occurs in about 836,000 to 2.5 million Americans. It’s estimated, however, that 84 to 91 percent are yet to be diagnosed.

There are no lab tests to screen for CFS, and its symptoms are similar to many other illnesses. Many people with CFS don’t “look” sick, so doctors may not recognize that they’re ill.

In order to be diagnosed with CFS, your doctor will rule out other potential causes and review your medical history with you.

They’ll make sure that you have at least four of the above symptoms. They’ll also ask about the duration and severity of your unexplained fatigue.

Ruling out other potential causes of your fatigue is a key part of the diagnosis process. Some conditions whose symptoms resemble those of CFS include:

Many of the symptoms experienced with CFS are similar to symptoms of severe obesity, depression, or sleep disorders.

The side effects of certain drugs, such as antihistamines and alcohol, can mimic CFS as well.

Because the symptoms of CFS resemble those of many other conditions, it’s important not to self-diagnose and to talk to your doctor about your symptoms.

There’s currently no specific cure for CFS.

Each person has different symptoms and may therefore benefit from different types of treatment, aimed at managing the disease and relieving their symptoms.

Treating the symptoms includes working with families and healthcare providers to make a plan and discuss the possible benefits and harms of the therapies.

Addressing post-exertional malaise (PEM) symptoms

PEM occurs when after even minor physical, mental, or emotional exertion, symptoms become worse.

Worsening symptoms usually occur 12 to 48 hours after the activity and last for days or even weeks.

Activity management, also called “pacing,” can help balance rest and activity to avoid PEM flare-ups. You’ll need to find your individual limits for mental and physical activities, plan these activities, and then rest to stay within these limits.

Some doctors refer to staying within these limits as the “energy envelope.” Keeping diaries may help you find your personal limits.

It’s important to note that while vigorous aerobic exercise is good for most chronic illnesses, people with ME/CFS don’t tolerate such exercise routines.

Home remedies and lifestyle changes

Making some changes to your lifestyle can help reduce your symptoms.

Limiting or eliminating your caffeine intake will help you sleep better and ease your insomnia. You should limit your nicotine and alcohol intake, too.

Try to avoid napping during the day if it’s hurting your ability to sleep at night. Create a sleep routine: You should go to bed at the same time every night and aim to wake up around the same time every day.

Medications

Typically, no one medication can treat all of your symptoms. Also, your symptoms may change over time, so your medications may have to, too.

In many cases, CFS can trigger or be a part of depression, and you may need an antidepressant for it.

If lifestyle changes don’t give you a restful night’s sleep, your doctor may suggest a sleep aid. Pain-reducing medication can also help you cope with aches and joint pain caused by CFS.

Alternative medicine

Acupuncture, tai chi, yoga, and massage may help relieve the pain associated with CFS. Always talk to your doctor before beginning any alternative or complementary treatments.

Despite increased research efforts, CFS remains a poorly understood condition with no cure. Managing CFS can therefore be challenging.

You’ll likely need to make major lifestyle changes in order to adapt to your chronic fatigue. As a result, you may experience depression, anxiety, or social isolation, so some people find that joining a support group can be helpful.

CFS progresses differently in different people, so it’s important to work with your doctor to come up with a treatment plan that meets your needs.

Many people benefit from working with a team of healthcare providers, including doctors, therapists, and rehabilitation specialists.

If you’re living with this condition, the Solve ME/CFS Initiative has resources that you may find helpful. The CDC also offers recommendations for managing and living with CFS.