Validation of the Oxford Depression Questionnaire: Sensitivity to change, minimal clinically important difference, and response threshold for the assessment of emotional blunting

Background: The Oxford Depression Questionnaire (ODQ) is a patient-reported scale for assessing emotional blunting in patients with major depressive disorder (MDD). This analysis was undertaken to further validate the scale in patients experiencing emotional blunting while receiving antidepressant treatment. Methods: Patients with MDD who experienced inadequate depressive-symptom resolution and emotional blunting on selective serotonin reuptake inhibitor or serotonin-noradrenaline reuptake inhibitor monotherapy (adequate dose for ≥6 weeks) were switched to vortioxetine 10-20 mg/day. ODQ total scores were assessed excluding and including the "antidepressant-as-cause" domain (ODQ-20 and ODQ-26, respectively). Anchor- and distribution-based methods were used to determine the minimal clinically important difference in ODQ scores in terms of change from baseline to week 8 of antidepressant treatment. Results: After 8 weeks of vortioxetine treatment, the mean change in ODQ-20 and ODQ-26 scores from baseline was -24.8 and -30.1 points, respectively. Greater mean changes from baseline in ODQ-20 and ODQ-26 scores were seen in patients reporting no emotional blunting vs those still experiencing emotional blunting after 8 weeks of vortioxetine treatment (ODQ-20: -27.0 vs -22.6 points; ODQ-26: -32.8 vs -27.5 points, respectively). In patients considered clinically minimally improved (Clinical Global Impression-Improvement score, 3) after 8 weeks of vortioxetine treatment, respective mean (standard deviation) change in ODQ-20 and ODQ-26 score from baseline was -15.5 (18.1) and -20.0 (20.5) points. Limitations: Short study duration. Conclusions: These results provide further validation of the clinical utility of the ODQ for assessing emotional blunting in patients with MDD. The suggested minimal clinically important difference for change in ODQ-20 and ODQ-26 scores is 16 and 20 points, respectively, after 8 weeks of antidepressant treatment. Trial registration: ClinicalTrials.gov identifier: NCT03835715.