IOM's clinical criteria for SEID diagnosis:
- Substantial reduction or impairment in the ability to engage in pre-illness levels of occupational, educational, social, or personal activities
- Postexertional malaise
- Unrefreshing sleep
- Either cognitive impairment or orthostatic intolerance (or both)
Note that the SEID criteria do not require the identification of any specific biological, biochemical, or neuroanatomical abnormality. Rather, they entail a substantial degree of distress and impairment.