Introduction: Depressive disorders are one of the most common psychiatric disorders. Recognition of signs of mental health disorders is not always easy, hence the availability of simple and accurate tools for assessing them is very important in the practice of primary care.
Objective: The aim of the study is to assess the theoretical accuracy and reliability of the Patient Health Questionnaire-9 (PHQ-9) in Polish conditions, when applied to general population studies for adults aged between 35-64.
Material and methods: The study comprised a population of 4,040 people. Women constituted 59% of the research population and people living in the countryside 65%. The average age of participants was 53.45 ± 7.05 years. According to PHQ-9, 727 people (18.0%) had moderate, moderate to severe or severe depression. PHQ-9 showed a significant positive internal cohesion (Cronbach's alpha = 0.77), and factor charges oscillated between 0.43-0.63, and the R2 coefficients of determination were in the range of 0.21-0.40.
Conclusions: The Polish version of PHQ-9 is a valid tool for diagnosing depression in the general population aged 35-64. Good psychometric properties and compactness make the PHQ-9 a useful clinical and research tool.
Keywords: PHQ-9; depression severity; general population; psychometric assessment.