Reading the Esketamine Evidence for Treatment-Resistant Depression

The short answer

Esketamine helps some people with treatment-resistant depression, but the benefit is modest and the evidence carries real limits. When Johnson & Johnson won U.S. approval for Spravato (esketamine) as a standalone treatment on January 21, 2025, the pivotal four-week trial reported 22.5 percent of patients reaching remission versus 7.6 percent on placebo. That gap is statistically real and matters to the people it helps, yet it also means most treated patients did not remit within a month. The drug can only be given inside a certified program with hours of in-office monitoring, and that requirement is itself a piece of evidence, because regulators judged the risks serious enough to police the treatment tightly rather than hand it out like an ordinary pill.

This is educational, not medical advice. The goal here is to show how to read the numbers, not to tell anyone whether to start or stop a treatment.

What the approval trial actually showed

The 2025 monotherapy indication rested on a randomized, double-blind, placebo-controlled study in adults with treatment-resistant depression, defined as inadequate response to at least two oral antidepressants. Participants received esketamine nasal spray alone or a placebo spray for four weeks. J&J reported remission in 22.5 percent of the esketamine group against 7.6 percent on placebo, with separation from placebo visible as early as 24 hours.

Two habits help when reading a figure like this. First, read the placebo arm alongside the drug arm rather than fixating on the drug arm alone. A 22.5 percent remission rate sounds underwhelming on its own, but the honest comparison is against the 7.6 percent who remitted on an inert spray. The difference of roughly 15 percentage points is what the drug adds. Second, translate that difference into people. A gap of about 15 points means that for every seven or so patients treated, one additional person reaches remission who would not have on placebo. That is a real effect. It is also far from the near-universal response that marketing language around glutamate and synaptic repair can imply.

Why a single four-week window is not the whole story

Depression is a chronic, relapsing condition, and a four-week endpoint answers only a narrow question about whether the drug can move symptoms quickly. It can. What a short trial cannot settle is whether that improvement holds for months, how patients fare when treatment stops, or how the drug performs against the harder outcomes that matter most, such as suicidality.

These are not new worries. When esketamine was first cleared as an add-on therapy in 2019, a widely cited critique in The Lancet Psychiatry laid out seven concerns about the efficacy data and the approval itself, including marginal separation from placebo after the first week, thin long-term controlled evidence, and weak signals against suicidality. Independent bodies reached cautious conclusions too. The prior evidence base leaned on trials such as TRANSFORM-2, where the average benefit over placebo on the standard depression rating scale was on the order of a few points, a change that is measurable but sits at the modest end of what antidepressant augmentation typically delivers.

The appraisal continues into 2026. A registered report published on medRxiv sets out a protocol for an individual patient data meta-analysis of the randomized, double-blind, placebo-controlled esketamine trials. Its very rationale is that the pooled, patient-level evidence has not been examined as rigorously as the drug's prominence would suggest, and that questions about effect size and durability deserve a harder look. A protocol is a plan, not a verdict. That researchers are still writing plans to re-examine the foundational data is the point worth noticing.

The blinding problem

One issue deserves special attention because it is easy to miss. Esketamine produces noticeable dissociation and sedation. Patients often know whether they received the active drug, which can undermine the blind that placebo-controlled trials depend on. When participants can guess their assignment, expectation alone can inflate the measured benefit, especially on subjective scales like self-reported mood. This does not mean the effect is imaginary. It means the true drug-specific effect could be smaller than the raw numbers suggest, and it is one reason a 15-point remission gap should be read as an upper-bound estimate rather than a floor.

What REMS tells you about the harm side

Esketamine is available only through a Risk Evaluation and Mitigation Strategy, a restricted-distribution program the FDA reserves for drugs whose risks require active management. Under the Spravato REMS, the medicine can be administered only in certified healthcare settings, and patients must be monitored for at least two hours after each dose for sedation, dissociation, blood-pressure changes, and, rarely, respiratory depression. The label also flags abuse and misuse potential, and esketamine is a controlled substance.

Read structurally, a REMS is a regulator's statement about the benefit-harm balance. Approval means the agency concluded the benefit outweighs the harm for a defined population. A REMS on top of approval means it reached that conclusion only on the condition that the harm is contained by mandatory safeguards. The two-hour observation window is not a formality. It exists because the adverse effects are common enough and serious enough that trained staff need to be present when they occur. When you weigh whether a treatment is worth it, that supervision requirement belongs on the harm side of the ledger alongside the efficacy numbers on the benefit side.

How to read numbers like these

A few principles travel well beyond this one drug. Compare the drug arm to the placebo arm, then convert the difference into how many people you would treat to help one. Ask what the trial did not measure, particularly long-term outcomes and the endpoints that matter most to patients. Check whether the blind could have leaked through unmistakable side effects. And treat a restricted-distribution requirement as data, not paperwork, since it encodes how seriously regulators take the harms. Esketamine is a genuine option for people who have exhausted standard antidepressants. The evidence supports calling it useful and rapid for some, while the same evidence argues against calling it a breakthrough that resolves the condition for most.