Reversed or chaotic diurnal sleep rhythms

Many patients with ME/CFS end up with circadian abnormalities ranging from severe delayed sleep phase to non 24 hour circadian rhythm disorder to apparent loss of regular circadian rhythms.



Canadian Consensus Criteria
The Canadian Consensus Criteria (CCC) for ME/CFS states that some form of sleep dysfunction will be present in almost all ME/CFS patients, and includes sleep dysfunction not caused by sleep apnea as a diagnostic criteria. "Reversed or chaotic diurnal sleep rhythms" are examples of sleep dysfunction involving circadian rhythm disruption, and are listed as a possible manifestation of sleep dysfunction in the Canadian Consensus Criteria for ME/CFS. At least one form of sleep dysfunction is required for diagnosis according to the Canadian Consensus Criteria.