Mood Disorders in Neurodegenerative Diseases

Mood disorders constitute a significant clinical problem in patients with a wide range of neurodegenerative disorders. This article reviews recent empirical studies examining depression, anxiety, and mania/disinhibition in patients with focal lesions (stroke), primary subcortical degeneration (Parkinson's disease), and primary cortical degeneration (Alzheimer's disease). Although each neuropsychiatric condition has unique clinical correlates, several common themes can be identified and include similarities in prevalence, neuroanatomic substrate, neurochemistry, and treatment response. Depression, for example, is associated with frontal lobe (primarily left hemisphere) dysfunction in stroke, Parkinson's disease, and Alzheimer's disease, whereas mania and dishinhibition are associated with dysfunction of ventral frontal and ventral temporal structures in both stroke and Alzheimer's disease. These similarities across distinctly different neuropathological conditions can provide important validation of fundamental neuroanatomical, as well as possible psychosocial pathways for the development of mood syndromes in neurological disease. The study of neuropsychiatric syndromes represents an important but relatively understudied area of research, that may ultimately help to illuminate the causes and specific treatments of these important clinical disorders.