The Effect of Melatonin on Cognitive Function in Patients Diagnosed With Mild Cognitive Impairment

Inclusion Criteria: 1. MCI assessment according to the Peterson et al. (2001) criteria. 2. Age 55-90 years, inclusive. 3. Study informant available. 4. Mini Mental Status Examination ; MMSE 24-30. 5. Adequate vision and hearing for neuropsychological testing. 6. Normal vitamin B12 level and thyroid function. Exclusion Criteria: 1. Significant cerebral vascular disease (Modified Hachinski scale \> 4). 2. Depression (Hamilton Depression Rating Scale \> 12). 3. Central nervous system infarct, infection or focal lesions of clinical significance on CT or MRI scans. 4. Medical diseases or psychiatric disorders that could interfere with study participation. 5. Pregnant, lactating or childbearing potential. 6. Taking vitamin supplements or other supplements. 7. Restrictions on concomitant medication usage, including those with significant cholinergic or anti-cholinergic effects or potential adverse effects on cognition.