Three hundred twenty respondents in selected geographic areas were interviewed with a structured questionnaire that included the Zung Self-Rating Depression Scale. Dimensional analysis indicates that some items are not pure measures of the constructs they were originally intended to assess. Moreover, some of the dimensions within the scale apparently convey different meanings to different segments in the population. In addition, different dimensions within the scale have varying demographic correlates.
The analysis suggests that in order for the scale to be a truly useful device for assessing depressive symptomatology in a general population, additional items need to be added and some questions need to be followed by probes to clarify the exact frame of reference of the respondents.
Blumenthal MD. Measuring Depressive Symptomatology in a General Population. Arch Gen Psychiatry. 1975;32(8):971-978. doi:10.1001/archpsyc.1975.01760260035002