 - Patients with previous use of alcohol or illicit drugs within seven days of randomization will be excluded. Preexisting unstable cardiovascular disease including uncontrolled hypertension will be excluded. Patients with a documented allergy to donepezil will also be excluded. Patients with axis I disorders eg. schizophrenia, schizoaffective disorder other than major depressive disorder, anxiety disorders andor bipolar depression will be excluded. Patients on anticoagulant therapy or chronic NSAID therapy will be excluded. Patients who are pregnant or wish to become pregnant within one year from trial enrollment will also be excluded. Patients who have received ECT within 6 months of enrollment will be excluded. Baseline Mini Mental State Examination MMSE 24 will be excluded. 