Longitudinal outcomes of patients with pseudodementia: a systematic review

Depression and a number of other psychiatric conditions can impair cognition and give the appearance of neurodegenerative disease. Collectively, this group of disorders is known as 'pseudodementia' and are important to identify given their potential reversibility with treatment. Despite considerable interest historically, the longitudinal outcomes of patients with pseudodementia remain unclear. We conducted a systematic review of longitudinal studies of pseudodementia. Bibliographic databases were searched using a wide range of search terms. Two reviewers independently assessed papers for inclusion, rated study quality, and extracted data. The search identified 18 studies with follow-up varying from several weeks to 18 years. Overall, 284 patients were studied, including 238 patients with depression, 18 with conversion disorder, 14 with psychosis, and 11 with bipolar disorder. Irrespective of diagnosis, 33% developed irreversible dementia at follow-up, 53% no longer met criteria for dementia, and 15% were lost to follow-up. Considerable variability was identified, with younger age at baseline, but not follow-up duration, associated with better outcomes. ECT and pharmacological interventions were also reported to be beneficial, though findings were limited by the poor quality of the studies. Overall, the findings suggest that pseudodementia may confer an increased risk of irreversible dementia in older patients. The findings also indicate, however, that a significant proportion improve, while many remain burdened with their psychiatric condition, independent of organic dementia. The findings support the clinical value of the construct and the need for its re-examination in light of developments in neuroimaging, genomics, other investigative tools, and trial methodology.