Development and cross-cultural testing of the International Depression Symptom Scale (IDSS): a measurement instrument designed to represent global presentations of depression.

Background: Self-report measurement instruments are commonly used to screen for mental health disorders in Low and Middle-Income Countries (LMIC). The Western origins of most depression instruments may constitute a bias when used globally. Western measures based on the DSM, do not fully capture the expression of depression globally. We developed a self-report scale design to address this limitation, the International Depression Symptom Scale-General version (IDSS-G), based on empirical evidence of the signs and symptoms of depression reported across cultures. This paper describes the rationale and process of its development and the results of an initial test among a non-Western population.

Methods: We evaluated internal consistency reliability, test-retest reliability and inter-rater reliability of the IDSS-G in a sample N  = 147 male and female attendees of primary health clinics in Yangon, Myanmar. For criterion validity, IDSS-G scores were compared with diagnosis by local psychiatrists using the Structured Clinical Interview for DSM (SCID). Construct validity was evaluated by investigating associations between the IDSS-G and the Patient Health Questionnaire (PHQ), impaired function, and suicidal ideation.

Results: The IDSS-G showed high internal consistency reliability ( α  = 0.92), test-retest reliability ( r  = 0.87), and inter-rater reliability ( ICC  = 0.90). Strong correlations between the IDSS-G and PHQ-9, functioning, and suicidal ideation supported construct validity. Criterion validity was supported for use of the IDSS-G to identify people with a SCID diagnosed depressive disorder (major depression/dysthymia). The IDSS-G also demonstrated incremental validity by predicting functional impairment beyond that predicted by the PHQ-9. Results suggest that the IDSS-G accurately assesses depression in this population. Future testing in other populations will follow.