This article offers a critical review of the published research concerning the prevalence of depressions, psychotic symptoms and disorders of behaviour in patients with Dementia of the Alzheimer Type (DAT). For any of these types of psychopathology there is much diversity in the reported prevalences. Controlled studies seem to indicate that patients with DAT have an increased prevalence of psychotic symptoms and disorders of behaviour but not of depressions. Higher rates of disorders of behaviour are encountered in patients with more serious dementia.

Information about the relationship between the prevalences of depressions or psychotic symptoms and the stage of the dementia is less uneqivocal. There is much variation in the applied diagnostic methods and the studied populations. No attention was paid to the overlapping symptoms of DAT and psychopathology. The conclusion is that up till now the knowledge concerning the prevalence of psychopathology in DAT is very global.