Behavioral and Psychiatric Symptoms of Dementia and Rate of Decline in Alzheimer's Disease.

Alzheimer's disease causes both cognitive and non-cognitive symptoms. There is increasing evidence that the presentation and course of Alzheimer's disease is highly heterogenous. This heterogeneity presents challenges to patients, their families, and clinicians due to the difficulty in prognosticating future symptoms and functional impairment. Behavioral and psychiatric symptoms are emerging as a significant contributor to this clinical heterogeneity. These symptoms have been linked to multiple areas of neurodegeneration, which may suggest that they are representative of network-wide dysfunction in the brain. However, current diagnostic criteria for Alzheimer's disease focus exclusively on the cognitive aspects of disease. Behavioral and psychiatric symptoms have been found in multiple studies to be related to disease severity and to contribute to disease progression over time. A better understanding of how behavioral and psychiatric symptoms relate to cognitive aspects of Alzheimer's disease would help to refine the models of disease and hopefully lead to improved ability to develop therapeutic options for this devastating disease.