Early research indicated that hallucinations and delusions would come and go in a rather unpredictable fashion, but this view has since been challenged . Recently, several reports have indicated that delusions and hallucinations are persistent, often lasting from 3 months to more than 1 year. In a large nursing home study, 69 % of the patients who displayed dementia with psychosis at baseline still had psychotic symptoms 1 year later .
Psychosis seems to be associated with a more severe phenotype of dementia. The cognitive decline is more rapid, and dependence is higher in dementia with psychosis than in dementia without psychosis. Furthermore, it seems that the higher rate of cognitive decline is apparent also before the onset of psychosis . It should be noted that antipsychotic drugs, which are often used to treat PiD, are also associated with increased cognitive impairment. Other adverse outcomes of PiD are increased burden on family and professional caregivers, earlier institutionalisation, greater functional impairment and increased mortality risk .