DEPRESSION IN THE PATIENT: Signs of depression in patients with Alzheimer's disease are difficult to detect because they change over time and vary in intensity and duration. Estimated frequency depends greatly on the evaluation scale (Cornell scale, Geriatric Depression Scale, Behave-Alzheimer disease scale, Cohen-Mansfield scale, Neuropsychiatric Inventory (NPI)). Several risk factors have been identified including early age of disease onset, female gender, etc). The anatomic basis of depression is essentially related to the noradrenergic and serotoninergic systems. DEPRESSION IN THE CAREGIVER: Caregivers bear a heavy burden, psychologically (30-50% of all cases of depression), physically, and financially. Depression in the caregiver favors depression in the patient, and vice versa. Episodes may develop at any time during the disease course. Decompensation depends on both patient-related and caregiver-related factors. IMPORTANCE OF DETECTING DEPRESSION: Depression is frequent, both in the patient and in the caregiver and must be detected and treated early. It has been demonstrated that 50% of the caregivers may be affected, but only 10-20% are treated.