Psychometric properties of the PHQ-9 measure of depression among Brazilian older adults.

: To obtain evidence on the psychometric properties of the Patient Health Questionnaire - 9 (PHQ-9, one of the most extensively used tools for assessing depression) in the Brazilian older population. Data on 3,356 Brazilian adults aged 60+ years living in Guarulhos, São Paulo state were used. The factor structure of the questionnaire was analysed using a factor analysis approach. The questionnaire's measurement equivalence was tested across gender, age, personal income, and education level groups. The scores were compared across groups based on the highest level of equivalence achieved. The questionnaire's internal consistency was analysed considering its factor structure. A one-factor solution was identified as the most adequate factor structure, with the factor explaining 57.6% of the items' variance. The correlation of the resulting latent score with the overall raw sum score in the PHQ-9 was  = 0.96. Measurement equivalence regarding thresholds and loadings was achieved for all tested groups. On average, women, older, less educated, and poorer people had higher latent scores on the depression factor. The measure showed a good internal consistency with Revelle's omega total ω=0.92. The results suggest that, among Brazilian older adults living in Guarulhos, São Paulo state, the PHQ-9 measures depressive symptomatology equivalently across different sociodemographic subgroups. Moreover, it can be scored using the raw sum of the item scores to adequately reflect different levels of depressive symptomatology.