Overview of SEID (Systemic Exertion Intolerance Disease)

Alternate Name for Chronic Fatigue Syndrome

SEID stands for systemic exertion intolerance disease, which is a new name for chronic fatigue syndrome put forth in an Institute of Medicine report published in February 2015.

Out-of-breath woman with her hands on her knees
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"Systemic" means that it affects the entire body.

"Exertion intolerance" refers to the hallmark symptom of ME/CFS, which is called post-exertional malaise. It causes people to suffer a major upturn in symptoms after even mild exertion. Some people are able to tolerate mild or moderate levels of activity, while others are unable to even take care of their most basic needs without consequences to their health.

The use of "disease" in the new name marks the first time this illness has been recognized as a disease (as opposed to a syndrome) in an official capacity.

Advocating for a Different Name

Chronic fatigue syndrome advocates have long called for a new name because the old one trivializes the condition and makes it sound like people with it are just sleepy instead of severely ill.

This new name shrugs off the stigma of and misunderstandings about "chronic fatigue syndrome" by:

  • Letting people know it's a body-wide affliction,
  • Putting forth the defining symptom,
  • And, at long last, recognizing it as a disease.

Still, this is a name that's not likely to catch on.

Over the last several years, many people in the patient, advocate, and research community have adopted some version of myalgic encephalomyelitis: ME, ME/CFS, or CFS/ME. The panel behind the report, though, says there's not enough scientific evidence to support that name. Much of the medical community agrees. Meanwhile, a lot of people using ME have a strong emotional attachment to it and are unlikely to give it up.

An older name that's still used by some patients is CFIDS, which stands for "chronic fatigue and immune dysfunction syndrome."

4 Sources
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.
  1. The Lancet. What’s in a name? Systemic exertion intolerance disease. The Lancet. 2015;385(9969):663. doi: 10.1016/S0140-6736(15)60270-7

  2. Stussman B, Williams A, Snow J, et al. Characterization of post–exertional malaise in patients with myalgic encephalomyelitis/chronic fatigue syndrome. Front Neurol. 2020;11:1025. doi: 10.3389/fneur.2020.01025

  3. Froehlich L, Hattesohl DB, Cotler J, Jason LA, Scheibenbogen C, Behrends U. Causal attributions and perceived stigma for myalgic encephalomyelitis/chronic fatigue syndrome. J Health Psychol. 2021. doi: 10.1177/13591053211027631

  4. What is cfids? Journal of Christian Nursing. 2008;25(1):43. doi: 10.1097/01.CNJ.0000306004.27747.ce

Additional Reading

By Adrienne Dellwo
Adrienne Dellwo is an experienced journalist who was diagnosed with fibromyalgia and has written extensively on the topic.