Alzheimer's disease is the most frequent cause of dementia (60% of all dementias) and affects nearly 300 000 people in France. Alzheimer's disease is a disease of the elderly which generally begins after 60 years and whose prevalence increases markedly after age 75 years. The elderly population is increasing in all Western countries. Alzheimer's disease thus constitutes a veritable emergent public health problem. The rapid inflation of the epidemiological and etiopathogenetic data have contributed to enhanced nosographic definition and finer semiological characterization of the disease. Thus, the classic concept of senile dementia has been totally abandoned. In contrast the concept of depressive pseudodementia as defined by Kiloh (1961) remains present in the <<psychiatric culture>>. The concept refers to rare clinical situations in which the controversial concept of <<test therapy>> with antidepressants retains, in the author's opinion, some utility. Depressive or psychobehavioral signs and symptoms frequently inaugurate Alzheimer's disease giving rise to first-line psychiatric management The use of multidimensional evaluation instruments such as the neuropsychiatric inventory (NPI) has enabled demonstration of the signs and symptoms and their quantification through the course of the disease. In the dementia stage, the psychobehavioral symptoms are related to the patient's awareness of the degradation in his intellectual functions and the loss of independence and to specific neuropathological lesions responsible for <<frontal deafferentation>>. Certain clinical forms of depression of late onset are also characterized by symptoms reflecting hypofrontal signs (blunted affect, apathy, defective initiative, etc.) and severe cognitive disorders. Those depressions are associated with risk factors shared with Alzheimer's disease (sex, age, vascular function, APOE 4) and constitute a risk factor for progression to dementia, requiring regular clinical and neuropsychological follow-up. Now that we are entering the era of therapy for Alzheimer's disease, the psychiatrist must contribute to the collective effort of early diagnosis and treatment. In close collaboration with all the medical and social professionals involved, the psychiatrist has a fundamental role throughout the disease, towards the patient but also in providing support and psychological assistance for caregivers.
