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.