A comparison of the psychometric strengths of the public-domain Zung Self-rating Depression Scale with the proprietary Beck Depression Inventory-II in Barbados.

OBJECTIVE To compare the psychometric strengths of two venerable measures of depression, the Zung Self-rating Depression Scale (Zung SDS) and the Beck Depression Inventory-II (BDI-II) in a Caribbean university student population and to provide researchers and clinicians interested in measures of depression with psychometric evidence that differentiates the two instruments for a Caribbean sample. METHODS Undergraduate student volunteers (n = 415; 75% females, 25% males; mean age = 25.2 years) completed the instruments as part of a larger study. Correlational analyses evaluated internal con-sistency reliabilities. Missing value analyses and corrected item-total correlations are also reported for each scale. RESULTS The BDI-II demonstrated marginally superior internal consistency reliability (alpha = 0.88) than the Zung SDS (alpha = 0.85). Correlation between the Zung SDS and the BDI-II was strong (r = 0.67, p < 0.01). The Zung SDS was less psychometrically adequate, only 53% of respondents (compared to 81% for the BDI-II) completed the entire form, suggesting that the structure or wording of the questions may be problematic. Comparison of corrected item-total correlations and missing value analyses indicates that many Zung SDS items are problematic. A preliminary effort to evaluate the factor structure of the Zung SDS was complicated by the large number of missing values. CONCLUSION Head-to-head comparison of the Zung SDS and the BDI-II indicates that the BDI-II demonstrates superior psychometric properties. This paper does not evaluate sensitivity and specificity; nonetheless, researchers interested in measures of depressive symptoms and clinicians looking for a tool to assess depression in Barbados can be confident in the strong psychometric properties of the BDI-II demonstrated thus far Modified versions of the Zung SDS merit further research.