Melatonin and Zinc Administration on Cardinal Symptoms in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Inclusion Criteria: 1. Patients between 18 and 65 years of age. 2. Patients with ME/CFS who met the diagnostic criteria (2011 ICC criteria) from the Central Sensitization Syndrome Unit (USSC) at the Vall d'Hebron University Hospital. 3. Patients who freely give written consent. Exclusion Criteria: 1. Any active medical condition that explained chronic fatigue (untreated hypothyroidism, sleep apnea, narcolepsy, medication side-effects). 2. Previous diagnosis not unequivocally resolved (chronic hepatitis, malignancy). 3. Past or current psychiatric disorders (major depressive disorder with psychotic or melancholic features, bipolar disorder, schizophrenia, delusional disorder, dementias, anorexia nervosa, bulimia nervosa). 4. Participation in another clinical trial of the same or different nature in the 30 days prior to study inclusion. 5. In the judgment of the investigator, inability to follow the instructions or to complete the treatment satisfactorily. 6. Failure to provide signed informed consent. 7. Current consumption of medications that may interfere with the results and/or whose withdrawal may be a relevant problem. 8. Anticoagulant treatment. 9. Pregnancy or breast-feeding, or had not used oral contraceptives or other hormonal preparations in the previous 6 months. 10. Smoking, alcohol intake or substance abuse. 11. Severe obesity (class 3 BMI ≥ 40 kg/m2). 12. Hypersensitivity to melatonin and/or zinc dietary supplements.