Treatment-resistant depression describes major depression that has not improved enough after adequate trials of at least two different antidepressants. An adequate trial means a therapeutic dose taken for roughly six to eight weeks. The definition is practical rather than biological: it identifies people who need a different approach instead of another similar medication. Research gives a sense of how common this is. In the STAR*D study, the largest real-world antidepressant trial, only about one third of patients reached remission on their first medication, and the odds fell with each subsequent attempt.
TRD does not mean untreatable. It means the standard first steps were not enough, and it opens the door to options with different mechanisms. These include augmentation with a second medication such as an atypical antipsychotic or lithium, switching to a different class, structured psychotherapy, Deep TMS and Spravato. Both TMS and Spravato are specifically indicated for people in this situation, and insurance plans generally require documentation of prior medication trials before approving them. A careful evaluation also matters: undiagnosed bipolar disorder, thyroid disease, sleep apnea, substance use or ongoing stressors can all make depression look resistant when the real problem is elsewhere. At Stedfast Psychiatry, a TRD consultation reviews your history, confirms the diagnosis, and lays out the interventional options available at our offices.