You have been taking Lexapro, Zoloft, Wellbutrin, or another antidepressant for weeks. Maybe it took the edge off; maybe it did nothing. Either way, it is not unusual. In the largest study ever run on this question, only about a third of people reached remission on their first antidepressant. The good news is that "not working" has become a much more specific problem than it used to be, with more answers, including approved treatments that did not exist a few years ago and trials designed for people in exactly your position.
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How long does it take for antidepressants to work?
Longer than most people expect. SSRIs such as Lexapro (escitalopram), Zoloft (sertraline), and Prozac (fluoxetine), and other antidepressants such as Wellbutrin (bupropion), typically need four to eight weeks at a full dose before their effect can be judged, and side effects usually appear before benefits do. Doctors often look for early signs by week two, such as slightly better sleep or energy, but the decision that a medicine is not working is normally made after six to eight weeks at an adequate dose. If you stopped early, or the dose was never raised to a therapeutic level, the medicine may not have had a fair trial, and that is the first thing a prescriber checks.
Signs your antidepressant is not working
After six to eight weeks at a proper dose: your mood, sleep, and energy are no better; you feel numb or "flat" rather than better; you improved at first and then slid back; or you are still unable to do the things depression stopped you doing. A partial response, feeling somewhat better but not well, counts too. Research shows that people who reach full remission relapse far less often than those who only partly improve, so "a bit better" is a reason to keep working on treatment, not to settle. Never stop or change a dose on your own; some antidepressants cause withdrawal symptoms when stopped abruptly, and only your prescriber can adjust them safely.
What doctors usually try next
There is a standard sequence, and most people move through it faster than they expect. Adjusting the dose, since many people start low and never reach the range that works. Switching to a different antidepressant, either within the same class or to a different one, such as moving from an SSRI to bupropion or an SNRI. Adding a second medicine, called augmentation; several medicines are approved specifically as add ons to an antidepressant. Adding psychotherapy, especially cognitive behavioral therapy, which improves results at every step. And checking for other causes: thyroid problems, sleep apnea, alcohol use, and bipolar disorder, in which antidepressants alone can make things worse, all mimic a "failed" antidepressant. Our guide to depression treatment options walks through each step.
If you are still on your first antidepressant and it is not enough, two studies are testing new add-on options for exactly this point, before depression is considered treatment resistant.
Treatment resistant depression: when two medicines have not worked
If two different antidepressants, each taken at an adequate dose for long enough, have not brought relief, doctors call it treatment resistant depression. It is common: in the STAR*D study, about a third reached remission on the first medicine and fewer on each later step, and a 2023 reanalysis found the often quoted two thirds cumulative remission rate was closer to a third. That label matters because it unlocks treatments that are not offered earlier. Esketamine nasal spray (Spravato) was approved in 2019 alongside an antidepressant and in January 2025 on its own; in its trial, about 22 percent of people reached remission within four weeks, versus about 8 percent on placebo. Auvelity, a combination of dextromethorphan and bupropion approved in 2022, works faster than standard SSRIs. Transcranial magnetic stimulation, a non invasive brain treatment cleared by the FDA in 2008, is given in daily sessions over several weeks. And electroconvulsive therapy remains the most effective option for severe depression. These are the treatments of people for whom pills have not worked, and they are exactly where research is moving fastest.
Trials designed for people whose antidepressant has not worked
This is the part most articles skip. A large share of depression research is built specifically around inadequate response: the eligibility criteria literally require that one or two antidepressants have failed. Psilocybin assisted therapy for treatment resistant depression has completed Phase 3 trials and is heading toward an FDA decision. New medicines with mechanisms unrelated to serotonin are in Phase 2 and 3. Home based brain stimulation, deep brain stimulation for the most severe cases, and studies that use blood or brain markers to predict which antidepressant will work are all recruiting. Most are placebo controlled or compare against standard care, so no one is promised the study treatment, and you continue to see your own doctor.
Studies recruiting now for exactly this situation
If you have tried only one antidepressant so far, two studies for adults whose depression is not well controlled on a single antidepressant are enrolling now.
A Phase 2 trial of ACP-211, a new medicine taken on its own, enrolls adults 18 to 65 whose depression has not improved on at least two antidepressants, at 26 US sites. A Phase 3 trial of esketamine nasal spray versus placebo enrolls adults with treatment resistant depression at 7 US sites. A home based study of transcranial direct current stimulation enrolls adults 18 to 85 with a documented inadequate response to antidepressants. Each listing spells out the exact requirements, and applying takes about 5 minutes. More are on our depression clinical trials page.
Lexapro, Zoloft, Wellbutrin, Prozac: does the specific drug change the answer?
Less than people think. Large comparisons find small differences in effectiveness between antidepressants, and none reliably predicts who will respond. What differs is side effect profile and, for Wellbutrin, mechanism: it works on dopamine and norepinephrine rather than serotonin, so it is a common switch when an SSRI has not helped, and vice versa. If Lexapro or Zoloft has not worked after eight weeks at a full dose, the question is not "which SSRI next" but "which of the next steps," and a prescriber will usually pick based on your symptoms, other conditions, and side effects you want to avoid.
Common questions
Why is my antidepressant not working? The most common reasons are that it has not had enough time, the dose is too low, it is not being taken consistently, or another condition is driving the symptoms. About a third of people also simply do not respond to a given medicine, which is why switching and adding are standard steps.
How many antidepressants should you try before something else? Most guidelines treat two adequate trials as the point where the diagnosis becomes treatment resistant depression and other options such as esketamine, TMS, or a clinical trial come into play. There is no rule that you must try many in a row.
Can I join a depression trial while taking an antidepressant? Often, yes. Many trials for inadequate response add the study treatment to your current antidepressant; others require a washout first. The listing says which, and the study team coordinates any change with your prescriber. Read about washout periods.
Is it safe to stop an antidepressant that is not working? Not on your own. Several antidepressants cause discontinuation symptoms if stopped suddenly, and stopping without a plan can worsen depression. A prescriber can taper one medicine while starting another.
See depression clinical trials recruiting now
Browse open studies, filter by location, and apply in about 5 minutes: Depression Clinical Trials