van Heukelom, R O, Prins, J B, Smits, M G et al. · European journal of neurology · 2006 · DOI
This study tested whether melatonin could help reduce fatigue in ME/CFS patients who have a delayed internal body clock. Twenty-nine patients took 5 mg of melatonin for 3 months timed to their natural sleep-wake rhythm, and researchers measured changes in their fatigue using a validated questionnaire. The treatment improved fatigue, concentration, motivation, and activity levels, with the biggest improvements seen in patients whose body clocks were most delayed.
Many ME/CFS patients have disrupted circadian rhythms that may contribute to their fatigue, making this one of the first studies to systematically test whether restoring circadian timing can alleviate core ME/CFS symptoms. This work opens a pathway for identifying ME/CFS patients who might benefit from chronobiotic interventions and supports the biological basis of circadian dysfunction in the disease.
This study does not prove that melatonin is effective for all ME/CFS patients—only those with significantly delayed melatonin secretion. The lack of a placebo control group means some improvement could be due to expectancy effects or natural variation over time. It also does not establish whether melatonin itself or the correction of circadian rhythm is the active mechanism.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
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