Prevalence and clinical correlates of psychotic symptoms in Alzheimer's disease.

Psychotic symptoms occur commonly in Alzheimer's disease (AD), predict a more rapid rate of cognitive decline and increase the risk of aggressive behaviour. Seventy patients with probable AD, recruited from an old age psychiatry service, were assessed to determine the prevalence and clinical correlates of delusions and hallucinations. Psychiatric symptoms were measured using the Behavioural Pathology in Alzheimer's Disease Rating Scale (BEHAVE-AD), Hamilton Rating Scale for depression (HRSD) and the Depressive Signs Scale (DSS). Thirty-four per cent of the sample experienced delusions and 11% hallucinations in the previous month. Men were more likely than women to have experienced psychotic symptoms. Psychotic and non-psychotic groups did not differ in age, age at illness onset, dementia severity, HRSD or DSS scores. This study confirms the high prevalence of psychotic symptoms in AD patients encountered in clinical practice, and suggests that psychosis and depression represent independent behavioural disturbances in AD.