Myalgic encephalomyelitis, also known as chronic fatigue syndrome, is a long-term illness that brings severe tiredness along with many other symptoms that can make everyday life difficult or even impossible for those affected.

Understanding the Scale of the Problem

Chronic fatigue syndrome affects millions of people around the world, though many remain undiagnosed. In the United States alone, estimates suggest that up to 3.3 million people suffer from this condition. What makes these numbers even more striking is that more than 9 in 10 people with the illness have not received a proper diagnosis from a doctor. This hidden epidemic costs the U.S. economy approximately $18 to $51 billion annually in medical expenses and lost income.^[1]

The disease can strike anyone regardless of age, gender, or ethnic background. However, certain patterns emerge when looking at who gets diagnosed most often. Among adults, women are affected more frequently than men. The condition most commonly appears in people of middle age, though it also impacts children, teenagers, and elderly individuals. Among younger patients, teenagers tend to be more affected than younger children.^[1]

One important consideration when examining these statistics is that people who are white are diagnosed more often than individuals from other racial and ethnic backgrounds. However, this does not necessarily mean the disease affects white people more frequently. Rather, many people with chronic fatigue syndrome remain undiagnosed, especially among racial and ethnic minority groups.^[1] This diagnostic gap points to broader issues in healthcare access and medical awareness.

In Australia, the scope of the problem is similarly significant, with estimates suggesting that up to 600,000 Victorians may be living with the condition. Alarmingly, as many as 90% of these individuals remain undiagnosed.^[7] Research indicates that 75 to 80 percent of people with this disease are female.^[7]

What Causes Chronic Fatigue Syndrome

Despite years of research, the exact cause of chronic fatigue syndrome remains unknown. This uncertainty makes the condition particularly frustrating for both patients and healthcare providers. What experts do understand is that the illness likely results from a combination of different factors working together, rather than a single trigger.^[2]

Many theories exist about what sets off this complex condition. Research shows that chronic fatigue syndrome is a biological illness, not a psychological disorder. Various mechanisms and biochemical changes have been identified that affect how the body functions. These include changes to the immune system, problems with hormonal regulation, and altered responses to oxidative stress. Scientists have also found evidence of natural killer cell dysfunction, T-cell dysfunction, elevated cytokines, and the presence of autoantibodies in some patients.^[4]

Several potential triggers have been identified that might spark the onset of chronic fatigue syndrome. Infections appear to play a significant role, as research suggests that certain viruses and bacteria might trigger or cause flare-ups of symptoms. These include Epstein-Barr virus (which causes infectious mononucleosis), Ross River virus, C. burnetii, and COVID-19.^[5] For some people, the disease appears suddenly after an infection, while in others it may develop gradually over months or even years.^[7]

Beyond infections, other potential triggers include toxic exposure, anesthetic procedures, immunizations, or physical trauma such as a car accident. Surgery and both physical and emotional stress have also been proposed as possible triggering factors. However, it’s important to note that no single trigger or abnormality has been found that is shared by everyone with chronic fatigue syndrome.^[4] Long after these triggering factors have occurred, the illness continues to affect patients.

Scientists are also investigating the role of genetics in this condition. Increasing evidence supports genetic susceptibility, with many studies reporting that family history plays a role in developing chronic fatigue syndrome or similar fatigue-like symptoms. Studies from twin registries have shown increased familial patterns, suggesting that the condition may run in biological families and might be genetic. However, more research is needed to identify the specific genes involved.^[4]

Research clearly demonstrates that chronic fatigue syndrome is not caused by being unfit or having mental health problems. Rather, it appears that problems with how the body produces energy at a cellular level may leave less fuel available for the brain and muscles. Additionally, like some autoimmune conditions, chronic fatigue syndrome may cause the immune system to mistakenly attack healthy parts of the body.^[5]

Risk Factors That Increase Susceptibility

While anyone can develop chronic fatigue syndrome, certain groups face higher risk. Understanding these risk factors can help individuals and healthcare providers stay alert to early warning signs, though having risk factors doesn’t guarantee someone will develop the condition.

Age plays a significant role in who develops chronic fatigue syndrome. Adults between the ages of 40 and 60 represent the most commonly affected age group. Among younger people, adolescents between 10 and 19 years old are more likely to develop the condition than younger children.^[5] This doesn’t mean that people outside these age ranges are immune, but rather that these groups should be particularly aware of symptoms.

Gender represents another important risk factor. Females are significantly more likely to develop chronic fatigue syndrome than males. This gender difference is consistent across different studies and populations, though researchers are still working to understand why women face higher risk.^[5]

Having a family history of chronic fatigue syndrome or similar fatigue-like symptoms increases an individual’s risk. This family connection suggests that genetic factors may make some people more susceptible to developing the condition when exposed to potential triggers.^[4]

Limited access to healthcare may also represent a risk factor, though in a different sense. People who lack access to knowledgeable healthcare providers may be less likely to receive proper diagnosis and early treatment. Similarly, the lack of healthcare providers who know about chronic fatigue syndrome and how to recognize it means that many people remain undiagnosed and therefore unable to access appropriate management strategies.^[1]

Recognizing the Symptoms

Chronic fatigue syndrome causes a wide range of symptoms that can vary significantly from person to person. The severity of symptoms can also fluctuate from day to day, making the condition unpredictable and difficult to manage. Understanding these symptoms is crucial for both recognizing the condition and managing daily life with it.

The primary symptoms that define chronic fatigue syndrome are quite specific. First and foremost is severe fatigue that doesn’t improve with rest or sleep and lasts for at least six months. This isn’t ordinary tiredness that goes away after a good night’s sleep. Instead, it’s a profound exhaustion that persists no matter how much someone rests. The fatigue must be severe enough that it prevents people from doing activities they used to do before becoming ill.^[6]

A hallmark feature of the condition is something called post-exertional malaise, often abbreviated as PEM. This means that symptoms get worse after any physical or mental activity. The worsening can begin shortly after the exertion or several days later, with symptoms typically becoming more severe 12 to 48 hours after the activity. These heightened symptoms can last for days or even weeks. Activities that trigger this response don’t have to be strenuous; even everyday tasks like showering, buying groceries, brushing teeth, or interacting with others may bring on post-exertional malaise.^[6][9]

Sleep problems represent another core symptom. People with chronic fatigue syndrome often have difficulty falling asleep or staying asleep. They may feel like they haven’t slept properly even after a full night’s rest, waking up feeling exhausted or stiff. Some people sleep too much, while others can’t get enough restful sleep. Some may find themselves sleeping during the day and staying awake at night.^[3][5]

Problems with thinking and memory are common and distressing. Often referred to as “brain fog,” these cognitive difficulties can include forgetfulness, confusion, trouble concentrating, and problems with attention and memory. People may have difficulty finding words or need to write things down when they previously could remember multiple things at once.^[3][5]

Many people experience orthostatic intolerance, which means symptoms worsen while standing or sitting upright. This can cause feelings of lightheadedness, dizziness, weakness, or faintness when standing up or sitting up from a lying position.^[6]

Beyond these primary symptoms, chronic fatigue syndrome can cause numerous other problems throughout the body. Pain is common, including muscle aches, joint pain, and headaches. The pain can affect different parts of the body and may come and go. Some people develop sore throats and tender, swollen lymph nodes in the neck or armpits. These flu-like symptoms can make people feel as though they have a persistent infection, even when they don’t.^[3][5]

Digestive problems can include symptoms similar to irritable bowel syndrome, such as painful bloating, gas, constipation, and diarrhea. People may also experience chills, night sweats, mood swings, irritability, tingling or numbness in the feet, hands or face, vision problems, and general weakness.^[5]

Patients may also become extra sensitive to various stimuli, including light, sound, smells, food, and medicines. What might be mildly irritating to others can become overwhelming for someone with chronic fatigue syndrome.^[2]

The symptoms can look and feel like the flu, and they often trigger after an infection. They can come and go, with periods when symptoms improve followed by times when they worsen. The unpredictable nature of the condition adds to the difficulty of managing daily life.^[5]

Prevention Strategies

Because the exact cause of chronic fatigue syndrome remains unknown, there are no proven strategies to prevent the condition from developing in the first place. However, for people who already have the condition, certain approaches may help prevent symptom worsening and reduce the frequency and intensity of relapses.

The most important preventive strategy for people with chronic fatigue syndrome involves learning to pace activities. This means finding individual limits for mental and physical activity and then planning activities and rest periods to stay within those limits. Healthcare providers and patients sometimes refer to staying within these limits as staying within the “energy envelope.” When people with chronic fatigue syndrome have good days, they may feel tempted to try and “push” themselves to make up for lost time. However, this often leads to a “crash,” or worsening of symptoms, which can then repeat itself in a difficult cycle.^[9]

Keeping activity and symptom diaries can help people with chronic fatigue syndrome find their personal limits, especially early in their illness. By recording daily activities, energy levels, and symptom patterns, people can begin to see what triggers worsening symptoms and what helps them feel better. This information becomes invaluable in learning to manage energy and prevent post-exertional malaise.^[9]

Maintaining a healthy, balanced diet is important for everyone and particularly benefits people with chronic fatigue syndrome. Eating regularly throughout the day, perhaps three meals and three snacks, might help keep energy levels more stable. Some people find it helpful to avoid sugar, sweeteners, alcohol, and caffeine, as these can affect energy levels unpredictably.^[10][17]

Establishing good sleep habits represents another key preventive strategy. This includes going to bed and waking up at the same time each day, keeping the bedroom cool, dark, and quiet, limiting alcohol intake in the evening, and not looking at screens right before bed. Winding down toward bedtime with relaxing rituals like meditation, yoga, journaling, reading, or taking a warm bath can help prepare the body for restful sleep.^[16]

Managing stress effectively may help prevent symptom worsening. Stress reduction techniques such as breathing exercises, meditation, gentle massage, or deep relaxation therapy might help some patients. However, people should talk with their healthcare providers about all therapies before beginning them.^[9][14]

While there is insufficient evidence to recommend specific supplements for preventing or treating chronic fatigue syndrome, people with the condition should ensure they are not deficient in essential nutrients. Those with biochemically proven deficiencies may benefit from appropriate supplementation under medical supervision.^[10]

How the Body Changes with Chronic Fatigue Syndrome

Chronic fatigue syndrome affects many body systems, causing widespread changes in normal physiological functions. Understanding these changes helps explain why the symptoms are so varied and why the condition is so challenging to treat.

The condition has been classified as a neurological disorder by the World Health Organization, though it affects many parts of the body beyond just the brain and nervous system. The term “myalgic encephalomyelitis” itself provides clues to these changes: “myalgic” refers to pain in the muscles, while “encephalomyelitis” means inflammation in the brain and spinal cord.^[7]

Scientists are beginning to understand some of the biological changes that occur in people with chronic fatigue syndrome. One major area of disruption involves the body’s ability to produce energy at a cellular level. Cells may have trouble converting food into energy, which leaves less fuel available for the brain and muscles. This fundamental problem with energy production helps explain why even small amounts of activity can leave people with chronic fatigue syndrome feeling completely exhausted.^[5][7]

The immune system undergoes significant changes in people with chronic fatigue syndrome. Research has identified natural killer cell dysfunction or T-cell dysfunction in many patients. These cells play crucial roles in fighting infections and maintaining health. Additionally, elevated levels of proteins called cytokines have been found, along with the presence of autoantibodies—proteins that mistakenly target the body’s own tissues. Like some autoimmune conditions, chronic fatigue syndrome may cause the immune system to attack healthy parts of the body by mistake.^[4][5]

Hormonal regulation is disrupted in people with chronic fatigue syndrome. The endocrine system, which produces and regulates hormones throughout the body, doesn’t function normally. These hormonal imbalances can affect multiple body processes, from energy levels to mood to sleep patterns.^[4][7]

Blood pressure and heart rate regulation are often impaired. This explains why many people with chronic fatigue syndrome experience orthostatic intolerance—problems maintaining normal blood pressure and heart rate when standing or sitting upright. When they stand up, their cardiovascular system doesn’t adjust properly, leading to dizziness, lightheadedness, or feeling faint.^[7]

The digestive system can be affected, leading to problems with how food moves through the intestines and how nutrients are absorbed. This may explain the digestive symptoms many patients experience, similar to irritable bowel syndrome.^[7]

Sleep architecture—the normal pattern of sleep stages throughout the night—becomes disrupted. People with chronic fatigue syndrome often don’t progress through sleep stages normally, which means they don’t get the restorative benefits of sleep even when they spend adequate time in bed. This helps explain why they wake up feeling unrefreshed no matter how long they’ve slept.^[7]

Cognitive function changes in ways that affect how quickly information is processed. The brain may not process information as efficiently as before the illness, leading to the problems with memory, concentration, and mental clarity that people describe as “brain fog.”^[7]