Prevalence, incidence and age at onset of psychiatric disorders in Norway

  Background: Increased demands for psychiatric services and increased rates of sickness absence for depression have raised the question of the occurrence of psychiatric disorders in Norway, and whether there is in fact a rising incidence rate. Methods: Between 1989–1991, 2015 and 617 persons participated in a two-phase population study. Phase I comprised screening by the Hopkins Symptom Check List 25 items (HSCL-25), and phase II a diagnostic interview by the Composite International Diagnostic Interview (CIDI), including report of date (year) of the first occurrence of any symptoms, and any consequent diagnosis: Results: A symptom score of 1.75 or more was found in 19.8% of the women and 9.3% of the men by the HSCL-25. Depression, anxiety or somatoform disorder by CIDI was found in 21.5% of the women and 11.5% of the men. The incidence rate increased significantly from 3.3 to 12.8 per 1000 person years from 1930 to 1991. The incidence rate in the year before the interview was 42.6 per 1000 person years. Age of onset became lower. More women became ill, but the illness seemed to last longer in men. A major problem in comparing results between studies is the different concepts and operationalisations of psychiatric illness, and the varying time periods given for estimates. Conclusion: The findings provide evidence of psychiatric illness being a rising and major health problem, but the role of recall bias must be further investigated.