If despite over 3 months of antidepressant treatment and/or psychotherapy, your patient has had less than 50% drop in PHQ-9 score, then criteria are met for refractory depression.
Could there be any of the following:
Undiagnosed or contributory medical condition?
Another psychiatric condition or issue such as
Any particular psychosocial issues (e.g. relationship, work, school) that might be contributing?
Any other factors?