Four-symptom criteria

The Four-symptom criteria, also known as the Four-item empiric criteria, is a definition of ME/CFS proposed by Leonard A. Jason.

Definition
Patients must fulfill all four criteria:
 * Post-exertional malaise
 * Fatigue
 * Unrefreshing sleep
 * A neurocognitive symptom

Studies

 * Chronic fatigue syndrome and myalgic encephalomyelitis: towards an empirical case definition
 * Chronic fatigue syndrome versus systemic exertion intolerance disease

Learn more

 * HealthRising - Excluding Factors: Jason Critiques the IOM Definition for ME/CFS