Patient Health Questionnaire-9 (PHQ-9)

The Patient Health Questionnaire-9 (PHQ-9) is a 9-item instrument for assessing depression commonly used in mindfulness research. It is both a measure of depression severity and a diagnostic measure of depressive disorders. The PHQ-9 has been translated and validated in multiple languages and contexts involving clinical and population-based samples. In terms of factor structure, a majority of existing studies recommend either a 1-factor model of depression or a 2-factor model with affective/cognitive (i.e., non-somatic) and somatic dimensions. The PHQ-9 is brief, freely available, and easy to score, has diagnostic utility as well as good psychometric properties, and can be administered in various ways, such as paper-based self-administration, telephone, smartphone custom app, and chatbot. Shorter and validated versions are available as PHQ-8 and PHQ-2 for the purpose of research or screening. Overall, the PHQ-9 is a useful tool for assessing depression.