Factor analysis of Zung Scale scores in a Japanese general population

The purpose of the present paper was to investigate the distribution of Zung Self-rating Depression Scale (SDS) scores in a general population and its factor structure. Questionnaires on SDS items were sent to 7136 randomly selected residents aged 20-79 years who lived in districts in Japan with high rates of suicide. Valid responses were received from 5547 residents (response rate: 77.7%). Factor analysis of the SDS scores was conducted. The SDS scores of the male subjects were significantly lower than those of the female subjects in all age groups. A reverse-J-shaped relationship was found between age groups and mean SDS scores for the male and female subjects. The highest mean score was in the age group of 20-39 years, and the lowest mean score was in the age group of 60-69 years for the male and female subjects. In factor analysis, two factors consisting of 12 items were extracted, and 10 of those 12 items covered six Diagnostic and Statistical Manual of Mental Disorders (4th edn; DSM-IV) criteria describing psychological disturbances of depression. The distribution of SDS scores differed depending on the age group. Major components of SDS in the subjects covered the DSM-IV criteria for psychological disturbances of depression.