Adaptation to San Martín Quechua and psychometric analysis of the Patient Health Questionnaire (PHQ-9) in Peruvian adults

Objective: To culturally adapt the Patient Health Questionnaire-9 (PHQ-9) for San Martín Quechua and to evaluate its structural validity, reliability, and measurement invariance in Peruvian adults. Methods: A psychometric study was conducted on a non-probabilistic sample of 309 Quechua-speaking adults from the San Martín region of Peru, including both men and women aged 18 to 59 years. The study was carried out in two phases. The first phase involved the translation and cultural adaptation of the original English PHQ-9 into the Quechua variant spoken in San Martín. The second phase tested how well the adapted PHQ-9 worked by using different methods: confirmatory factor analysis (CFA) to examine its internal structure, multi-group CFA to assess measurement invariance across groups, the Average Variance Extracted (AVE) to evaluate construct representation, and reliability estimation. Convergent validity was also examined through correlations with related measures. Results: A unidimensional model of the PHQ-9 Quechua San Martín showed adequate fit (CFI = 0.996, TLI = 0.994, SRMR = 0.048, RMSEA = 0.051) and high reliability (α = 0.86; Ω = 0.87). Measurement invariance was supported across sociodemographic groups (ΔCFI and/or ΔRMSEA < 0.01). Convergent validity was supported by an adequate AVE (0.53). Additionally, PHQ-9 scores correlated moderately with the Generalized Anxiety Disorder-7 and weakly and negatively with the Well-Being Index, supporting convergent validity based on relations with other variables. Conclusions: The San Martín Quechua PHQ-9 is a valid, reliable, and at least partially invariant single-factor instrument for assessing depressive symptoms in Quechua-speaking adults. It may be useful as a screening tool in similar populations.