RESUMEN
AIMS: This study evaluated the psychometric characteristics of the Polish version of the PHQ-9 in detecting major depression (MDD) and 'MDD and/or dysthymia' in people with and without type 2 diabetes. METHODS: Participants were randomly selected from a diabetes outpatient facility (N = 216) and from among patients admitted to a medical center and psychiatric hospital (N = 99). The participants completed the PHQ-9. The Hamilton Depression Rating Scale and the Mini International Neuropsychiatric Interview were used to identify the presence of psychiatric symptoms. The optimal cut-offs for PHQ-9 in people with and without type 2 diabetes were investigated based on two methods: 1) Youden's index which identifies cut-off points useful in scientific research; 2) a second method of two-stage screening for depressive disorders to provide guidance for clinical practice. RESULTS: The Polish version of the PHQ-9 is a reliable and valid screening tool for depression in people with and without type 2 diabetes. An optimal cut-off of ≥ 7 was indicated by Youden's index and ≥ 5 by the two-stage method for screening for MDD and 'MDD and/or dysthymia' in the group with type 2 diabetes. A cut-off of ≥ 11 was optimal for screening for both MDD and 'MDD and/or dysthymia' among people without diabetes (Youden's index). The two-stage approach suggested a ≥ 10 score for screening for MDD and ≥ 9 for screening for 'MDD and/or dysthymia' in people without diabetes. CONCLUSIONS: A lower cut-off score of the PHQ-9 is recommended for people with type 2 diabetes as compared to the general population.