The United States Centers for Disease Control and Prevention (CDC) recommends these criteria for diagnosis: # Greatly lowered ability to do activities that were usual before the illness. This drop in activity level occurs along with<unk>  and must last six months or longer. # Worsening of symptoms after physical or mental activity that would not have caused a problem before the illness. The amount of activity that might aggravate the illness is difficult for a person to predict, and the decline often presents 12 to 48 hours after the activity. The 'relapse', or 'crash', may last days, weeks or longer. This is known as post-exertional malaise (PEM). # Sleep problems; people may still feel weary after full nights of sleep, or may struggle to stay awake, fall asleep or stay asleep. Additionally, one of the following symptoms must be present: * Problems with thinking and memory (cognitive dysfunction, sometimes described as "brain fog") * While standing or sitting upright; lightheadedness, dizziness, weakness, fainting or vision changes may occur (orthostatic intolerance) Other common symptoms Many, but not all people with ME/CFS report: * Muscle pain, joint pain without swelling or redness, and headache * Tender lymph nodes in the neck or armpits * Sore throat * Irritable bowel syndrome * Chills and night sweats * Allergies and sensitivities to foods, odors, chemicals, lights, or noise * Shortness of breath * Irregular heartbeat The CDC proposes that persons with symptoms resembling those of<unk>  consult a physician to rule out several treatable illnesses: Lyme disease, "sleep disorders, major depressive disorder, alcohol/substance abuse, diabetes mellitus, hypothyroidism, mononucleosis (mono), lupus, multiple sclerosis (MS), chronic hepatitis and various malignancies." Medications can also cause side effects that mimic symptoms of<unk> . Central sensitization, or increased sensitivity to sensory stimuli such as pain have been observed in<unk> . Sensitivity to pain increases after exertion, which is opposite to the normal pattern. Onset Gradual or sudden onset of the illness may occur, and studies have mixed results as to which occurs more frequently. Physical functioning The functional capacity of individuals with<unk>  varies greatly. Some persons with<unk>  lead relatively normal lives; others are totally bed-ridden and unable to care for themselves. For the majority of persons with<unk> , work, school, and family activities are significantly reduced for extended periods of time. The severity of symptoms and disability is the same regardless of gender, and many experience strongly disabling chronic pain. Persons report critical reductions in levels of physical activity. Also, a reduction in the complexity of activity has been observed. Reported impairment is comparable to other<unk> ng medical conditions including late-stage AIDS, lupus, rheumatoid arthritis, chronic obstructive pulmonary disease (COPD), and end-stage kidney disease.<unk>  affects a person's functional status and well-being more than major medical conditions such as multiple sclerosis, congestive heart failure, or type II diabetes mellitus. Often, courses of remission and relapse of symptoms occur, which make the illness difficult to manage. Persons who feel better for a period may overextend their activities, and the result can be a worsening of their symptoms with a relapse of the illness. About 25% of people with<unk>  are house-bound or bed-ridden for long periods during their illness, often for decades. An estimated 75% are unable to work because of their illness. More than half were on disability benefits or temporary sick leave, and less than a fifth worked full-time. Children who become ill with<unk>  are a major cause of school absence. People with<unk>  have decreased scores on the SF-36 quality-of-life questionnaire, especially in the sub scales on vitality, physical functioning, general health, physical role, and social functioning; however, the sub scales for "role emotional" and mental health in<unk>  patients were consistent with or not substantially lower than healthy controls. Direct healthcare costs are estimated at between $9 and $14 billion annually in the U.S. alone. Cognitive functioning Cognitive dysfunction is one of the more disabling aspects of<unk>  due to its negative impact on occupational and social functioning. 50 to 80% of persons with<unk>  are estimated to have serious problems with cognition. Cognitive symptoms are mainly due to deficits in attention, memory, and reaction time. Measured cognitive abilities are found to be below projected normal values and likely to affect day-to-day activities; for example, increases in common mistakes, forgetting scheduled tasks, or having difficulty responding when spoken to are observed. Simple and complex information-processing speed, and functions entailing working memory over long time periods are moderately to extensively impaired. These deficits are generally consistent with the patient's perceptions. Perceptual abilities, motor speed, language, reasoning, and intelligence do not appear to be significantly altered. When poorer health status was reported, a person's perception of their cognitive problems was frequently greater. Better physical functioning in people with<unk>  is associated with less visuoperceptual difficulty and fewer language-processing complaints. Inconsistencies of subjective and observed values of cognitive dysfunction reported across multiple studies are likely caused by a number of factors. Differences of research participants' cognitive abilities pre and post illness onset are naturally variable, and are difficult to measure because of a lack of specialized analytical tools that can consistently quantify the specific cognitive difficulties in<unk> . The frequency of neuropsychiatric and neuropsychological symptoms is increased in the population of persons with<unk> ; the understanding of why this occurs is unresolved. Various hypotheses have been advanced to try to explain the relationship between the cognitive symptoms and the illness. Some researchers believe psychiatric causes underlie or contribute to the illness, while other researchers believe the illness causes biochemical and sociological changes in people that produce the symptoms.
Chronic fatigue syndrome
Hypothyroidism
Cancer-related fatigue
Idiopathic chronic fatigue
Da Costa's syndrome  Da Costa's syndrome  1
Exercise addiction
Medication phobia
Generalized anxiety disorder