This type of depression is not consistently defined. This type of depression is not an official DSM-5-TR diagnoses or subtype.
Descriptions of TRD:
Patients whose depressive disorder does not respond satisfactorily to adequate treatment (antidepressant trials) clearly have harder-to-treat depression, generally referred to as treatment-resistant depression (TRD). TRD is a complex phenomenon influenced by variety in depressive subtypes, psychiatric comorbidity, and coexisting medical illnesses. It poses a common, challenging presentation to psychiatric and primary care clinicians. (CMS, 2018)
Treatment-resistant depression (TRD) typically refers to inadequate response to at least one antidepressant trial of adequate doses and duration. TRD is a relatively common occurrence in clinical practice, with up to 50% to 60% of the patients not achieving adequate response following antidepressant treatment. (American Psychiatric Association, 2020)
But with treatment-resistant depression, standard treatments aren’t enough. They may not help much at all, or your symptoms may improve, only to keep coming back. (Mayo clinic, 2021)