Psychometric properties and clinical utility of brief measures of depression, anxiety, and general distress: the PHQ-2, GAD-2, and K-6

Objective: The nine-item Patient Health Questionnaire (PHQ-9), seven-item Generalized Anxiety Disorder scale (GAD-7), and ten-item Kessler Psychological Distress Scale (K-10) are valid and reliable measures of depression, anxiety and general distress. However, the time required in their administration may limit their use in routine care. This study examines the utility of shorter versions (PHQ-2, GAD-2, and K-6) as screening instruments and measures of treatment response. Method: Data from research trial participants (n = 993) receiving internet-delivered cognitive behaviour therapy (iCBT) were analysed to establish discriminant validity of the short versions. Mini International Neuropsychiatric Interview (MINI) diagnoses were used as comparators. Criterion group validity, test–retest reliability, internal consistency, and responsiveness to treatment changes were examined. Analyses were replicated using data from patients receiving iCBT in routine care (n = 1389). Results: Discriminant validity was excellent for the PHQ-2, and acceptable for the GAD-2 and K-6. Acceptable sensitivity and specificity were identified at a threshold of ≥3 for the PHQ-2 and GAD-2, and ≥14 for the K-6. The short versions were sensitive to treatment change. Conclusion: The PHQ-2, GAD-2 and K-6 are useful screeners and efficient measures of treatment progress and outcomes in routine clinical care.