Chronic Fatigue Syndrome Glossary, Page 1

This glossary defines some of the terms used in discussing Chronic Fatigue Syndrome, or Myalgic Encephalomyelitis.

Part A: Terms most often encountered in relation to CFS

A – H


acute phase
A short, sharp, and relatively severe course of a disease; not chronic.
Agents that reduce inflammation without directly antagonizing the agent that caused it.
Pharmaceutical agents used to treat clinical depression.
anxiety disorders
Also known as anxiety neurosis or anxiety reaction. A condition that can be caused by both psychologic and physiologic factors. It can take two general forms: (1) acute anxiety (panic disorder), marked by repeated occurrences of intense self-limited anxiety lasting usually a few minutes to an hour, or (2) chronic anxiety, characterized by less intense reactions of much longer duration (days, weeks, or months).


bipolar affective disorder
A mood disorder that commonly begins with depression and is characterized by at least one period of elation sometime during the course of the illness.
A genus of bacteria with numerous species that cause disease in humans. The diseases associated with these organisms are typically relapsing fevers.


Candida albicans
A common saprophyte of the digestive tract and female urogenital tract. It does not ordinarily cause disease, but may do so following a disruption of bacterial flora of the body, or in patients with depressed immune systems.
case definition
In the example of CFS, a combination of symptoms, signs, and physiologic characteristics that serve to distinguish a case of chronic fatigue syndrome from other disease states.
case-control study
An epidemiologic study that examines selected patients who have a defined disease (cases) with persons without the disease (controls).
Of long duration, denoting a disease of slow progress and long continuance.
chronic fatigue and immune dysfunction syndrome (CFIDS)
A synonym for chronic fatigue syndrome used by some patients and physicians. It should be stressed, however, that no immune dysfunction or aberration has been persuasively linked to chronic fatigue syndrome.
A substance that enhances or is necessary for the action of enzymes. They are generally much smaller than enzymes themselves.
connective tissue disorder
A variety of inflammatory diseases of connective tissue, the most common of which is rheumatoid arthritis. Much, if not all, of this disease is now attributed to autoimmune processes.
connective tissue
The supporting tissues of the body, such as tendons, ligaments, bone, and cartilage.
A device used to verify or regulate a scientific experiment or study. A case-control study serves as a useful example. Since patients with a specific illness are examined for various characteristics, a group of healthy individuals who otherwise have as much in common with the patients as possible must be examined in parallel for the same characteristics.
cross-sectional study
In epidemiology, a study in which participants are examined at only a single time for characteristics of a disease.
Proteins manufactured by cells of various lineages that, when secreted, drive specific responses (e.g., proliferation, growth, or maturation) in other susceptible cells.
cytomegalovirus (CMV)
One of the eight known types of human herpesviruses, also known as human herpesvirus 5 (HHV-5). It belongs to the beta subfamily of herpesviruses. CMV can cause severe disease in patients with immune deficiency and in newborns when the virus is transmitted in utero.


A neurotic or psychotic condition marked by an inability to concentrate, insomnia, and feelings of dejection and guilt.


A genus of RNA viruses with over 70 types identified in humans. They reproduce in the intestinal tract, and various members can cause a variety of human diseases, including poliomyelitis, aseptic meningitis, hepatitis, inflammatory heart disease, and rhinitis.
The branch of medical science that deals with the incidence, distribution, and control of disease in a population.
Epstein-Barr virus (EBV)
One of the eight known types of human herpesviruses, also known as human herpesvirus 4 (HHV-4). It belongs to the gamma subfamily of herpesviruses. It commonly causes acute mononucleosis, and less commonly chronic mononucleosis. It some populations EBV is causally associated with life-threatening malignancies (Burkitt’s lymphoma, nasopharyngial carcinoma).
Causal association of a disease with an agent. The study of the cause of diseases.


Also known as myofascial pain syndrome and fibromyositis. A group of common rheumatoid disorders (not involving the joints) characterized by achy pain, tenderness, and stiffness of muscles.


A family of large DNA viruses that infect a wide range of animal species. Eight distinct types have been associated with a variety of human diseases.
human herpesvirus 6
A virus of the herpesvirus beta-subfamily, discovered in 1985, that infects more than 95% of people by the age of 2 years. It has been causally associated with roseola, mononucleosis-like illness, inflammation of lymph glands. There is also suggestive evidence for a role in multiple sclerosis.

All clinical material on this site is peer reviewed by one or more clinical psychologists or other qualified mental health professionals. This specific article was originally published by on and was last reviewed or updated by Dr Greg Mulhauser, Managing Editor on .

Overseen by an international advisory board of distinguished academic faculty and mental health professionals with decades of clinical and research experience in the US, UK and Europe, provides peer-reviewed mental health information you can trust. Our material is not intended as a substitute for direct consultation with a qualified mental health professional. is accredited by the Health on the Net Foundation.

Copyright © 2002-2022. All Rights Reserved.