[Psychiatric manifestations in dementia: phenomenologic perspectives].

The study of psychiatric manifestations in dementia has long been overshadowed by the more classical manifestations of the disease, such as memory loss and other cognitive deficits. In recent years, however, psychiatric symptoms as part of the demential process have attracted interest and research has become more specific. Clinicians are faced with diagnostic, treatment and management difficulties related to affective or psychotic symptoms, which account for much distress and morbidity. Several studies indicate that the prevalence of psychiatric manifestations in clinical populations of patients suffering from dementia is high: 15% to 30% for hallucinations, 15% to 30% for delusions, ten percent to 20% for major depression and 40% to 50% for depressed mood. These figures tend to confirm the hypothesis that psychiatric features in dementia are neither infrequent nor atypical. Thus, researchers have sought to link psychotic or depressive symptomatology with several clinical characteristics of dementia, namely stage, severity, prognosis or cognitive dysfunction. Some recent studies involving extensive neuropsychological evaluations indicate that subgroups of patients can be defined according to psychiatric criteria, as well as cognitive or neurological criteria. Unfortunately, results are inconsistent. Some of the contradictions in the literature are related to poorly defined terms and symptoms, a lack of reliable operational criteria, absence of validation of instruments and scales and heterogeneity of the populations studied. Ambiguous syndromes, such as pseudodementia, while illustrative of certain clinical situations, have not been helpful in categorizing demented patients. The author suggests that research focused on specific and clearly defined psychiatric symptoms in dementia will better serve our comprehension of mixed syndromes.