Ketamine for Depression: What the Evidence Shows

Ketamine has been a hospital anaesthetic since the 1970s, but its second life — a fast-acting treatment for severe depression — is what brings most people to this page. The evidence is interesting and, in places, genuinely strong; it is also more limited and provisional than the enthusiasm around it suggests. This review lays out what is established, promising, and still early, for patients and families rather than as clinical guidance. To see routes where you live, start with our eligibility check.

TL;DR Racemic ketamine, given by intravenous infusion, produces a rapid antidepressant effect that small controlled trials have shown consistently since 2006. But the effect is usually short-lived, repeated infusions are needed to maintain it, and relapse after stopping is common. It is used off-label almost everywhere in Europe — it is not an approved antidepressant. Ketamine-assisted psychotherapy is promising but under-evidenced. Repeated use carries bladder-damage and dependence risks. Norway's 2025 decision to fund it publicly for treatment-resistant depression is a real milestone, but still off-label and delivered under conditions.

What it is

Ketamine is a dissociative anaesthetic on the WHO list of essential medicines. The form used in most depression research and off-label treatment is racemic ketamine — a 50:50 mix of two mirror-image molecules, S-ketamine (esketamine) and R-ketamine. Esketamine (Spravato) is one of those two molecules, isolated and developed into an approved nasal-spray medicine with its own full trial programme (EMA overview); our separate esketamine evidence review covers it. Racemic ketamine is the older, cheaper, generic anaesthetic. It has never been through regulatory approval as an antidepressant, so its use for depression is off-label — legal, but outside its licensed indication.

Like esketamine, ketamine acts on the brain's NMDA glutamate receptors, which is thought to trigger downstream changes in mood-regulating circuits and explains why relief can arrive within hours rather than the weeks conventional antidepressants take.

Regulatory status in Europe. Racemic ketamine is a licensed anaesthetic, not a licensed antidepressant, in every EU country. Depression treatment therefore happens off-label, typically as intravenous infusions in a clinic under monitoring. That off-label status is the single most important fact for reading everything below.

What the evidence shows

Ketamine's evidence base is a mix of a strong core finding, a solid but qualified body of trial data, and several areas where honesty requires saying "we don't know yet."

Established: rapid antidepressant effect of intravenous ketamine

The foundational result is robust and has been replicated many times. In a landmark crossover trial, *Zarate et al. (Archives of General Psychiatry, 2006)* gave patients with treatment-resistant depression a single intravenous infusion of racemic ketamine or placebo. Within 24 hours, 71% met response criteria and 29% met remission criteria — a speed and magnitude of effect unlike anything conventional antidepressants offer (Zarate et al. 2006). The rapid, short-term antidepressant effect of a single infusion is the best-established fact in this entire field.

The Cochrane review by Caddy et al. (2015), "Ketamine and other glutamate receptor modulators for depression in adults," pooled the controlled trials and confirmed that ketamine produced a rapid antidepressant effect compared with placebo, while flagging the small sample sizes, short follow-up and difficulty of blinding as real limitations (Caddy et al. 2015). That combination — a real effect, on a shaky evidentiary base — is the honest summary of the acute data.

Promising and reasonably supported: repeated infusions and maintenance

The catch with a single infusion is that the benefit typically fades within one to two weeks. To hold the response, clinicians give repeated infusions. A meta-analysis by *Marcantoni et al. (Journal of Affective Disorders, 2020) synthesised a decade of IV-ketamine studies in treatment-resistant depression and confirmed both the rapid efficacy and its transience, with relapse common after infusions stop (Marcantoni et al. 2020). A widely cited synthesis by McIntyre et al. (American Journal of Psychiatry, 2021)* reached the same balanced conclusion: real and rapid, but with maintenance strategies still being worked out and long-term data thin (McIntyre et al. 2021). Promising, clinically useful evidence — but it does not yet answer how long people should stay on infusions or how to prevent relapse when they stop.

Early or mixed: ketamine-assisted psychotherapy (KAP)

Ketamine-assisted psychotherapy — pairing the dose with structured preparation and integration — is widely offered by private clinics and often marketed as if the combination were proven. The evidence does not support that framing yet. Recent systematic reviews describe KAP as promising but early: protocols are heterogeneous, controlled trials are few, and — crucially — no large study cleanly separates the psychotherapy from the drug effect (systematic review, Clinical Psychology Review, 2026; KAP for treatment-resistant depression, Psychopharmacology, 2026). It is reasonable to try KAP; it is not reasonable to present it as evidence-proven. The honest tier: promising, under-evidenced, worth doing in a properly screened setting with realistic expectations.

What is being studied now

Active research is trying to close the gaps the current evidence leaves. Trials are testing maintenance schedules, whether R-ketamine (the other enantiomer, thought to have fewer dissociative effects) works as an antidepressant, and how ketamine compares directly with esketamine. The KAP field is running controlled studies to isolate the psychotherapy component — the missing piece noted above. Because much of this work is small, early, or industry-linked, weigh the source; verify current studies on ClinicalTrials.gov and the EU registers, and see our trials guide for how phases, placebo and blinding shape what a study can show. Curated summaries of new papers are collected by the group's own research tool.

Safety and who should not take it

During an infusion, ketamine commonly causes dissociation, a short-lived rise in blood pressure and heart rate, nausea, dizziness and perceptual changes; these resolve as the drug clears, which is why sessions include monitoring and a recovery period. The risks that deserve real attention come with repeated or long-term use, and are evidence-based rather than alarmist.

Bladder and urinary-tract damage. Chronic ketamine exposure can cause ketamine uropathy (also called ketamine cystitis) — bladder inflammation, urinary urgency and pain, and in severe cases lasting damage. This is best documented in heavy recreational use, but it is a recognised concern for any repeated medical use, and urological bodies have issued consensus guidance on managing it (British Association of Urological Surgeons consensus, BJU International, 2024). Repeated-use programmes should monitor urinary symptoms.

Dependence and misuse. Ketamine has abuse potential, and repeated dosing carries a dependence risk — one reason the approved esketamine product is hemmed in by supervised administration and special-prescription controls (EMA EPAR), and one reason repeated racemic-ketamine treatment belongs in a monitored clinical setting. Expert syntheses treat misuse liability as a genuine consideration in any repeated-dosing plan (McIntyre et al. 2021).

Who should take particular care. Ketamine raises blood pressure, so uncontrolled hypertension and significant cardiovascular disease call for caution and specialist evaluation. A personal or family history of psychosis, active substance-use concerns, and pregnancy or breastfeeding are also reasons to reconsider or seek specialist input. A responsible clinic screens cardiovascular health, psychiatric history, current medicines and — for repeated programmes — urinary symptoms before starting; if a provider offers treatment without that assessment, treat it as a warning sign.

Legal status and how access works in Europe

Because racemic ketamine is a licensed anaesthetic, using it off-label for depression is legal across Europe — but that legality does not mean it is funded or easy to obtain. In most countries, ketamine depression treatment is private and self-pay, delivered by specialist clinics, with the notable exception of Czechia, where one clinic secures partial coverage from several insurers (Blossom: Czechia).

The clearest evidence-to-policy milestone came from Norway. In 2025, the national system for assessing new methods (Nye metoder / Beslutningsforum) decided to allow publicly funded intravenous racemic ketamine as a possible treatment for treatment-resistant depression in the specialist health service — to be delivered in hospitals or district psychiatric centres, via registry or study, for patients who have not responded to other approved treatments, and with patients informed that it is off-label use (Nye metoder decision). This is significant: a national body weighing the evidence and deciding it is strong enough to fund — while still surrounding it with conditions that reflect the evidence gaps this review describes.

For how coverage compares across twelve countries, see our Europe-wide reimbursement map; for what "licensed" means and how to spot a responsible clinic, see how to choose a ketamine or KAP clinic; and use the eligibility check to see which route may be open where you live.

Frequently asked questions

Is ketamine an approved treatment for depression in Europe?

No. Racemic ketamine is an approved anaesthetic, and it is used off-label for depression — legally, but outside its licence. The only approved medicine derived from it is esketamine nasal spray (Spravato), which has its own EU authorisation for treatment-resistant depression (EMA EPAR).

How fast does ketamine work, and how long does it last?

Fast, but not forever. A single infusion can lift depression within hours, with response rates around 70% at 24 hours in the foundational trial (Zarate et al. 2006). The benefit usually fades within one to two weeks, which is why repeated infusions are used and relapse after stopping is common (Marcantoni et al. 2020).

Is ketamine-assisted psychotherapy proven to work?

Not yet, in the strict sense. It is promising, but the evidence is limited and no large trial cleanly separates the psychotherapy from the drug effect (systematic review, 2026). Approach it with realistic expectations and a properly screened provider.

What are the risks of repeated ketamine treatment?

The two that matter most with repeated use are bladder and urinary-tract damage (ketamine uropathy) (urology consensus, 2024) and dependence or misuse. Both are reasons repeated treatment should be monitored in a clinical setting, with urinary symptoms tracked over time.

Why does Norway's decision matter?

Because a national body reviewed the evidence and decided it was strong enough to publicly fund ketamine for treatment-resistant depression — while still requiring specialist delivery and study-linked follow-up (Nye metoder). It is a signal of where the evidence stands: good enough to fund with conditions, not yet good enough to license as a standard antidepressant.

Sources

This review is for general information only and is not medical advice, a diagnosis, or a recommendation of any treatment. Off-label practice, reimbursement rules and clinical evidence change; always verify current information with your national regulator or a licensed clinician who knows your history. If you are in crisis, contact your local emergency number or a crisis line immediately.

This article awaits review by a licensed medical professional.