Patient Health Questionnaire-9 (PHQ-9, Dutch version)28
The PHQ-9 assesses depressive symptoms and consists of 9 items corresponding to DSM-V diagnostic criteria for major depression. It has demonstrated strong psychometric properties. Items are scored on a 4-point Likert scale: 0 (‘not at all’), 1 (‘several days’), 2 (‘more than half of the days’) or 3 (‘nearly every day’). Scores range from 0 to 27, with higher scores indicating more severe depressive symptoms. Scores can be divided according to level of severity: ‘minimal’ (scores 0-4), ‘mild’ (scores 5-9), ‘moderate’ (scores 10-14), ‘moderately severe’ (scores 15-19) and ‘severe’ (scores 20-27). The PHQ-9 also assesses suicidal ideation (question #9) which can accompany more severe depressive symptoms. Studies have shown that using a threshold score of 10 or higher has a sensitivity of .85 and specificity of 0.89.29