Depression symptoms across settings: Development and validation of the International Depression Symptom Scale
Haroz, Emily Edmunds
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Background: Existing measurement instruments for depression are most often based on symptoms observed in western clinical populations. It remains unclear whether these instruments are appropriate for use in epidemiologic, screening, intervention monitoring and evaluation, and clinical settings in non-western contexts. The overall goal of this study was to determine if there is a need for new instruments with global applicability to measure depression, and if so, to develop and test this new instrument. Methods: Two approaches were used in this process: 1) a systematic literature review of qualitative studies to identify common symptoms related to depression across populations; and 2) a quantitative analysis of existing datasets using item response theory (IRT) to identify how different symptom questions related to depression perform across settings. Results from these investigations were used to inform the development of the International Depression Symptom Scale (IDSS), an instrument designed to reflect global presentations of depression. The IDSS was tested in a community sample of adults (N = 147) in Yangon, Myanmar. Results: Results from the literature review and quantitative analysis indicated that most symptoms included in western definitions of depression and on existing measurement instruments are frequently mentioned and perform well across settings. However, additional symptoms need to be included in measurement instruments to more accurately reflect the presentation of depression all over the world. These include: social isolation, anger, hopelessness, thinking too much, confusion, and somatic complaints. The IDSS was developed based on these conclusions. Testing results showed that the IDSS had high internal consistency reliability (α = 0.92), test-retest reliability (r = 0.87) and inter-rater reliability (ICC = 0.90). Construct, criterion, and incremental validity were also supported for the IDSS. Preliminary evidence supports the IDSS use as a screening tool to detect depressive disorders and impaired functioning in this context. Further research needs to be done to explore its validity in other settings and its use as a clinical or epidemiologic tool. Conclusions: Findings contribute to our understanding of how depression manifests globally and demonstrates initial evidence to support the usefulness of a measurement instrument created to reflect the global presentation of depression.