How is "treatment-resistant depression" defined?

Treatment-resistant depression is defined as depression that does not respond adequately to two or more different antidepressant treatments administered at adequate doses and for an appropriate duration. This classification helps identify patients who may require more advanced or alternative therapeutic options, such as psychotherapy, augmentation strategies, or novel treatments. It emphasizes the challenge of finding effective interventions for individuals who do not experience significant symptom relief from standard antidepressant therapies, drawing attention to the need for personalized treatment approaches in mental health care.