Elderly patients with major depressive disorder and delusional disorder are at increased risk of subsequent dementia.

All the patients (n=150) admitted to psychogeriatric clinic during a 1-year period were followed up until their death or for 10 years. Fifteen of these were lost during the 10-year follow-up. Thus, follow-up data were available for 135 patients. Twenty-four of these fulfilled at baseline the DSM-III-R diagnostic criteria of major depressive disorder and 18 of delusional disorder after careful medical examination and neuropsychological tests to eliminate organic causes. In the follow-up, the diagnoses were gathered from the death certificates of those patients who died during the 10-year period and all of the patients alive at the end of the study were interviewed to assess their mental state. Six out of the 24 (25%) patients with major depressive and five out of 18 (28%) patients with delusional disorder developed clear organic dementia before death or within 10 years (mean follow-up time 6.7 years). This is approximately double the expected incidence in the general population of that age. The gender, age at index admission, the baseline Mini Mental State Examination scores or findings in computer tomography did not contribute to the risk of dementia. Psychogeriatric patients admitted due to major mental disorder may have an increased risk of organic dementia in the near future.