TRD is a widely used clinical construct rather than a formal diagnostic entity. It does not appear as a distinct diagnosis in DSM-5-TR, and there is no dedicated ICD-10-CM code. In practice it is documented in the clinical record and coded under the underlying major depressive disorder codes (F32.x for a single episode, F33.x for recurrent). No formally agreed diagnostic criteria exist.
The consensus operational definition across the literature is failure to achieve adequate response to at least two antidepressant trials of adequate dose and duration within the current episode, after confirming adherence and reassessing the diagnosis. Thresholds are not fully uniform across the field, but two adequate failed trials is the working bar this flag applies.
This flag surfaces patients who appear to have had at least two medication trials of adequate dose and duration, and who may therefore have TRD and be appropriate for escalation to interventional treatment.
Recommended next steps (CANMAT 2023)
Confirm clinically that the patient has in fact had at least two trials of adequate dose and duration (typically 6 to 8 weeks at a therapeutic dose), that adherence was adequate, and that the diagnosis holds. This rules out pseudoresistance, where apparent non-response reflects an inadequate trial rather than true resistance.
For patients with a partial response, adding adjunctive therapy is a reasonable step and is favored earlier under CANMAT 2023. It can be pursued alongside evaluation for interventional treatment.
Once the threshold is confirmed, consider escalation to interventional treatment.
CANMAT 2023: https://journals.sagepub.com/doi/full/10.1177/07067437241245384