Measurement of depression in the Brazilian population: validation of the Patient Health Questionnaire (PHQ-8)

Abstract

We aimed to evaluate the psychometric properties of the Brazilian version of the Patient Health Questionnaire (PHQ-8). A study with a sample of 4,170 individuals (≥ 15 years old) from the urban area. Conglomerate sampling was adopted in two stages (census sectors and streets), with weighting of estimates by sample weights. A structured questionnaire with sociodemographic data, the PHQ - the modules for depression, generalized anxiety disorder and panic disorder - and the Self-Reporting Questionnaire (SRQ-20) were used. In the evaluation of the PHQ-8, we verified the construct validity by analyzing the dimensional structure, convergent validity and internal consistency. We found a linear disorder without losses to maintain the four response categories. The factor analysis found unidimensionality of the depression construct, with strong factor loads, low residual variances, low residual correlation between items, good fit of the model, internal consistency and satisfactory convergent factorial validity (high loads and correlations with other tests/scales of similar constructs). The PHQ-8 has a one-dimensional structure with evidence of good validity and reliability, being suitable for use in the Brazilian population.