Methodological issues of an epidemiological study: From the results of a study on psychological problems seen in outpatients visiting the internal medicine departments of general hospitals

The frequency and type of psychological problems of outpatients in general healthcare settings, the recognition and management of those problems by ph ysicians, and the course of the problems were investigated using a two-stag e sampling design method. The subjects were outpatients visiting the depart ment of internal medicine of two general hospitals in Nagasaki prefecture. For the first-stage investigation, the General Health Questionnaire 12-item Version (GHQ-12) was used. A second-stage investigation was then conducted , which used many instruments containing the Composite International Diagno stic Interview (CIDI) and Groningen Social Disability Scale (GSDS). As a re sult, 1555 patients participated in the first-stage, 483 were selected and 336 (69.5%) participated in the second-stage investigation. No significant differences were seen in age or sex between the GHQ score groups among the 1555 subjects of the core sample. The background factors of the two hospita l samples differed significantly in the distribution of age, sex and physic al diseases. There were some differences in the participation between men a nd women in age and GHQ score. It was then suggested that variances should be considered in such an epidemiological study.