Cognitive impairment in elderly schizophrenia: a dementia (still) lacking distinctive histopathology.

Recent clinical and neuropsychological studies have shown that severe deterioration in cognitive and functional capacities is prevalent in elderly, chronically hospitalized patients with schizophrenia. Postmortem studies of tissue from patients who were clinically well characterized have found notably little neurodegenerative or other pathology to explain the dementia. In contrast, several large studies using archival material have reported an unexpectedly high occurrence of Alzheimer's disease pathology in patients with schizophrenia irrespective of clinical status. Reasons for conflicting results likely include inaccuracies in psychiatric diagnoses but also could be due to differences in sample selection, treatment histories, and environmental influences. Thus, the neurobiological substrates for dementia in late-life schizophrenia remain uncertain. Further studies should incorporate standard diagnostic procedures with community-based and institutionalized schizophrenia patients as well as psychiatric control patients with similar treatment histories. These should apply sensitive neuropathological methods to assess disease-specific and nonspecific markers of neurodegeneration and dementia.