Prevalence and clinical correlates of disinhibition in dementia

The phenomenology, main clinical correlates, and long-term evolution of disinhibition in dementia are not well known. To examine this issue, we studied a consecutive series of 272 patients with probable Alzheimer disease using a comprehensive psychiatric and neuropsychological evaluation that included the Disinhibition Scale. A subset of patients was reexamined with the same instruments between 1 and 4 years after the initial evaluation.

A factor analysis of the Disinhibition Scale demonstrated 4 factors: (1) abnormal motor behavior, (2) hypomania, (3) loss of insight and egocentrism, and (4) poor self-care. Disinhibition was significantly associated with major and dysthymic depression, more severe negative symptoms, and loss of awareness. Most patients with disinhibition at the initial evaluation still showed disinhibition at follow-up, whereas 23% of patients without disinhibition at the initial evaluation developed disinhibition at follow-up.

Disinhibition is a frequent and long-lasting problem in dementia. Our study demonstrates that the construct of disinhibition consists of 4 independent subsyndromes, each of which may have specific underlying mechanisms.