BACKGROUND: The literature was reviewed to abstract items which were claimed to 
distinguish organic dementia from pseudodementia. Their discriminating powers 
were tested in a prospective study. Eighteen of these items were selected to 
create a questionnaire which should distinguish organic dementia from 
pseudodementia. The gold standard was the final diagnosis given by a consultant 
psychiatrist 12-14 months later.
METHOD: One hundred and twenty-eight patients referred to our service with a 
differential diagnosis of depressive pseudodementia were screened using a 
checklist of 44 characteristic features (in the form of questions with 'yes' or 
'no' answers) which were claimed in the literature of differentiate between 
organic dementia and depressive pseudodementia. This checklist covers the areas 
of history, clinical data, insight and performance.
RESULTS: Forty points (questions) out of the 44 in the checklist showed 
significant discriminating power to differentiate dementia from depressive 
pseudodementia (p < 0.01). A principal component and factor analysis was 
performed from which 18 questions were extracted. The shortened questionnaire 
was able to classify (43/44 cases) 98% of dementia cases and (60/63) 95% of 
depression correctly. A new definition has been introduced for 'pseudodementia' 
as a syndrome of reversible subjective or objective cognitive problems caused by 
non-organic disorder. Thus depressive pseudodementia may be classified into two 
subtypes. Type I is a group of patients who have depressive symptoms with 
subject complaint of dysmnesia without measurable intellectual deficits. Type II 
is a group of patients who have depressive symptoms and show poor cognitive 
performance based on poor concentration not due to organic disorder.