THE GENERAL-POPULATION PREVALENCE OF NONORGANIC PSYCHIATRIC-DISORDERS IN SUBJECTS AGED 85 YEARS AND OVER

The prevalence of psychiatric disorders was investigated in all inhabitants over 85 years of age (N = 1259), residing in Leiden, The Netherlands. The study design consisted of two phases. In the first phase the Mini-Mental State Examination (MMSE) and the 12-item version of the General Health Questionnaire (GHQ- 12) were used to screen for potential cases; in the second phase all potential cases and a sample of the non-cases were interviewed with the Geriatric Mental State Schedule (GMS). DSM-III diagnoses were made based on the GMS and on information obtained from caregivers. There was a high prevalence of organic disorders of 31% (95% CI: 27-35%). The estimated overall prevalence rate for functional disorders was 8% (95% CI: 4-12%). This is an underestimate because organic and functional disorders are mutually exclusive in DSM-III. The prevalence rate estimated for the population at risk for functional disorders (i.e. the total population minus the organic cases) was 12% (95 % CI: 6-18%). This is very similar to prevalence rates for functional disorders found in population based surveys in younger age groups. Therefore, in contrast with the dementias, there appears to be no increase with age for the functional disorders.