K Guide

If you are in crisis or thinking about harming yourself, do not wait for an appointment. In the US, call or text 988 (Suicide and Crisis Lifeline).

This guide is information, not medical advice; see the Disclaimer at the end.

Which Ketamine Are We Talking About?

“Ketamine therapy” is not one thing. The same drug reaches patients through several pathways that differ in regulatory status, setting, and monitoring, and those differences matter for safety, cost, and what the evidence covers:

The rest of the guide takes these distinctions up in detail: what each pathway involves, what the evidence shows, what treatment costs, and how to evaluate a provider.

Who This Guide Is For

This guide is for anyone who wants to understand the science and the practical side of ketamine therapy: what it is, what it can and can’t do, and what the experience is like. It is written with several readers in mind:

• People considering ketamine therapy, including those living with chronic or treatment-resistant depression, or other conditions where ketamine has shown real benefit, who want a clear and honest picture before deciding whether it is right for them.

• Family members and friends helping someone navigate treatment, or who have questions and concerns of their own and want to understand what a loved one is going through.

• Clinicians who want a grounded understanding of how ketamine therapy works in practice: its benefits, its limits, and what people experience during and after treatment.

• Practitioners looking for a fair, well-sourced resource to share with prospective and current patients. Explaining what is genuinely known, what remains uncertain, and what to realistically expect is hard to do well, and good materials are scarce.

Why This Guide Exists

Ketamine therapy sits in an unusual place. The promise is genuine and the benefits are real. At the same time, there is a lot of confusion, marketing, and uncertainty. Most people have to navigate that complexity at the worst possible time, in the middle of a serious health problem that already makes hard decisions harder.

Much of the information available today comes from providers. It is often useful, but providers have an understandable incentive to emphasize benefits, and may say less about the risks, the alternatives, or the situations where ketamine is not the right tool.

This guide aims to be different: in-depth, fair, and independent. It covers the science and the facts alongside the practical and human side of treatment, without leaning in any particular direction. Ketamine is a tool, and like any tool in mental health it is valuable only when it is used well, in the right situation, and with the right support. The goal is to give you the context to understand it clearly and make an informed decision, for yourself or for someone you care about.

What Ketamine Therapy Is

Ketamine is a dissociative anesthetic — one that can produce a sense of detachment from one’s body and surroundings — used in surgery and emergency medicine since its FDA approval in 1970 (brand name Ketalar), and a Schedule III controlled substance. Beginning with a small but rigorous trial in 2000, researchers found that a single sub-anesthetic intravenous dose, typically 0.5 mg/kg infused over about 40 minutes, can relieve depression within hours in people who had not responded to conventional antidepressants. That finding opened the line of treatment now broadly called ketamine therapy.

Ketamine is a racemic mixture of two mirror-image molecules: (S)-ketamine (esketamine) and (R)-ketamine (arketamine). Most clinic-based treatment uses the racemic form, prescribed off-label, meaning the FDA has not approved it specifically for psychiatric use. Esketamine (Spravato), the (S)-enantiomer formulated as a nasal spray, is the exception: the FDA approved it in 2019 for treatment-resistant depression, in 2020 for depressive symptoms with acute suicidal ideation or behavior, and in 2025 as a standalone treatment for treatment-resistant depression. Because of risks including sedation, dissociation, and potential misuse, Spravato must be given in a healthcare setting certified under an FDA Risk Evaluation and Mitigation Strategy (REMS), with at least two hours of monitoring after each dose.

Routes and settings. Ketamine therapy is delivered in several ways, each with different bioavailability, onset, and level of medical oversight:

• IV infusion is the most studied route, with full (100%) bioavailability. A typical protocol is a 40-minute infusion in a clinic with continuous vital-sign monitoring.

• Intramuscular (IM) injection has high bioavailability (around 93%) and a faster onset, and is often used in ketamine-assisted psychotherapy.

• Intranasal esketamine (Spravato) is the only FDA-approved formulation for a psychiatric indication, self-administered under direct supervision in a certified setting.

• Sublingual and oral formulations (lozenges, troches, tablets) are compounded and prescribed off-label. Bioavailability is lower (roughly 25-30% sublingual, about 20% oral), so doses are higher. These forms anchor most telehealth and at-home models. In 2023, the FDA warned that at-home use of compounded ketamine without on-site monitoring raises the risk of harm from sedation and dissociation.

Infusions versus ketamine-assisted psychotherapy (KAP). A plain infusion or dosing session focuses on the drug effect: the patient receives ketamine, is monitored, and goes home after recovering. Ketamine-assisted psychotherapy pairs dosing with structured therapy, usually a preparation session beforehand, a therapist or guide present during the experience, and one or more integration sessions afterward to work through what comes up. KAP treats ketamine as a catalyst for therapeutic work, not only as a medication.

Screening, supervision, and integration support vary widely across these settings, from closely monitored in-clinic infusions and REMS-certified Spravato programs to lighter-touch telehealth. Those differences matter for safety, and are taken up in the sections on risks and on finding a provider.

How Treatment Works and What to Expect

There is no single ketamine protocol. Dose, route, and schedule vary by formulation and provider, but most approaches share a structure: an initial series of closely spaced sessions to establish a response, then less frequent maintenance to sustain it.

A typical IV ketamine course starts with an induction series of about six infusions over two to three weeks. The most studied dose is 0.5 mg/kg given intravenously over roughly 40 minutes, the protocol used in the foundational trials and reflected in the American Psychiatric Association’s consensus statement on ketamine for mood disorders. Blood pressure, heart rate, and oxygen saturation are monitored throughout, since ketamine can transiently raise blood pressure and heart rate. Most acute psychological effects fade within one to two hours. A visit, including intake, infusion, and observation, usually runs 1.5 to 2.5 hours.

Esketamine (Spravato) follows an FDA-specified schedule: for treatment-resistant depression, 56 mg or 84 mg intranasally twice weekly for four weeks, then weekly through week eight, then weekly or every two weeks, individualized to the least frequent dosing that holds the response. Under its REMS, each dose is given in a certified setting with at least two hours of monitoring. The prescribing information is the authoritative source for the schedule; for readable, patient-facing drug information on esketamine, see MedlinePlus.

The subjective experience varies from person to person. At sub-anesthetic doses, ketamine produces a dissociative state: altered perception of time, space, and body, a sense of floating, and visual or auditory distortions. Some people find it disorienting; others describe it as reflective or clarifying. Effects usually begin during the infusion and recede within an hour or two. Set and setting matter: a calm, supportive environment and clear expectations from the team can meaningfully shape the experience.

Cost and access are real barriers. IV ketamine for depression is off-label and usually not covered by insurance; out-of-pocket costs commonly run $400 to $800 per infusion, putting a six-session induction course around $2,400 to $4,800 or more. Spravato, as an approved product, is more often covered by commercial insurance and Medicare, though copays and prior-authorization rules vary. Ketamine is a Schedule III controlled substance; using it for depression is legal when prescribed and supervised by a licensed provider.

Response is not guaranteed, and benefits can fade. In studies, response usually means a substantial, clinically meaningful improvement on a standard depression scale (the exact threshold depends on the scale used); remission means symptoms fall to within the normal range. You can respond without reaching remission. In trials, roughly half to two-thirds of people with treatment-resistant depression respond to IV ketamine, but a single infusion’s effect typically lasts only days to about a week. Repeated infusions extend the benefit and maintenance dosing can sustain it for months, but relapse is common if treatment stops, often within two to three weeks. Ketamine works best as an ongoing part of a broader plan, alongside psychotherapy, other medications, and lifestyle change, not as a one-time cure.

Is ketamine therapy worth discussing for your situation? That decision belongs to you and your clinician, but these are the questions a careful clinician will work through with you:

• Where are you now? If you are in crisis, urgent care and the 988 lifeline come before any new-treatment plan.

• What have you already tried? The evidence is strongest for treatment-resistant depression — people who have not improved after adequate trials of standard treatments — not as a first-line option.

• Does your health history change the risk? Uncontrolled hypertension, pregnancy, and certain vascular conditions are contraindications, and psychosis or schizophrenia-spectrum disorders are standard exclusions (see Risks, Safety, and Contraindications).

• Which pathway is on offer? Spravato, off-label IV or IM, an at-home compounded program, and KAP differ in evidence, monitoring, and cost (see the pathway table at the top of this guide).

• Can you sustain it? Benefits usually require maintenance; weigh the ongoing cost and logistics, not just the induction series.

• What else is on the table? Other options for treatment-resistant depression, such as augmentation strategies, TMS, and ECT, may fit your situation better; a fair clinician compares them rather than defaulting to what they offer.

Risks, Safety, and Contraindications

Ketamine has real benefits, and like any active medication it also carries real risks. What matters is understanding those risks and how they differ across settings and patterns of use.

Acute effects. During or shortly after a session, ketamine commonly causes dissociation, sedation, dizziness, nausea or vomiting, and transient increases in blood pressure and heart rate. These effects are usually short-lived, resolving within one to two hours, and are manageable where vital signs are monitored. The blood-pressure rise is the most clinically significant acute concern; in esketamine trials it peaked roughly 40 minutes after dosing and returned to baseline within about four hours.

Bladder and urinary tract toxicity. Frequent, high-dose, or prolonged use can damage the bladder lining, causing ketamine-induced cystitis (urinary urgency, frequency, pain, and in severe cases reduced bladder capacity and blood in the urine). The evidence comes overwhelmingly from heavy recreational use; one review estimated that more than a quarter of regular recreational users develop lower urinary tract symptoms. In supervised therapeutic use at standard doses, urological problems appear uncommon: a 2025 systematic review of 27 psychiatric studies found urinary symptoms in 0% to about 25% of patients, generally mild, and the SUSTAIN-3 extension (esketamine, up to 6.5 years) reported no clinically significant urinary findings. A case of cystitis during therapeutic ketamine for depression has been reported. Clinicians should still monitor for urinary symptoms, and patients should report changes promptly.

Dependence and abuse potential. As a Schedule III drug, ketamine has a moderate potential for abuse and psychological dependence. Physical dependence is less prominent than with opioids or benzodiazepines, but psychological dependence can develop, particularly with unsupervised or frequent use. New-onset misuse has not been a notable problem in clinical trials of sub-anesthetic ketamine for depression, but the risk is worth an honest conversation, especially for people with a significant substance-use history.

Drug interactions. Combining ketamine with other central nervous system depressants raises the risk of excessive sedation, respiratory depression, and cardiovascular complications; the most important are alcohol, benzodiazepines, and opioids. Most providers advise avoiding alcohol and other sedating substances for at least 24 hours before and after a session. Benzodiazepines may also blunt ketamine’s antidepressant effect by dampening the glutamate surge thought to drive it, a separate reason some providers taper them before treatment.

Contraindications and cautions. The esketamine (Spravato) label contraindicates aneurysmal vascular disease, arteriovenous malformation, and a history of intracerebral hemorrhage, because ketamine raises blood pressure and the risk of vascular events. More broadly, uncontrolled hypertension is a strong contraindication, and a history of psychosis or schizophrenia-spectrum disorders is a standard exclusion, since dissociative effects may worsen psychotic symptoms. Pregnancy is contraindicated based on animal data suggesting fetal harm. Significant cardiovascular disease, moderate-to-severe liver impairment, or active substance use disorders call for careful, individual risk-benefit evaluation.

Unsupervised and at-home use. In 2023, the FDA warned about compounded ketamine used at home without medical monitoring, citing serious adverse events including respiratory depression. Without a clinician present to watch sedation, dissociation, and vital signs, the risks are substantially higher. The reassuring safety profile from clinical trials reflects screened, monitored, supervised sessions, not unsupervised self-administration.

Long-term safety in supervised use. The longest dataset on repeated therapeutic ketamine is the SUSTAIN-3 open-label extension of esketamine nasal spray. Final results (2025) followed 1,148 patients on intermittent esketamine plus an oral antidepressant for up to 6.5 years (about 3,800 patient-years) and found no new or unexpected safety signals, including for cognition and urinary health, with most adverse events transient and confined to dosing days. This is reassuring for supervised, intermittent use, but says nothing about unsupervised, frequent, or high-dose patterns.

Ketamine-Assisted Psychotherapy and Integration

Most ketamine treatment today is infusion-only: the patient receives the drug, is monitored, and goes home. Ketamine-assisted psychotherapy (KAP) adds a structured therapeutic frame around the dosing session. The idea is that ketamine’s neuroplastic and psychological effects open a window in which psychotherapy may be more effective, and that the experience itself is worth working with rather than just waiting out.

A typical KAP course has three phases:

• Preparation. Before the first dosing session, the patient meets with a therapist or guide to discuss goals, fears, and expectations, build rapport, and set an intention. This is also where practical matters are covered: what the drug feels like, what to do if the experience becomes difficult, and how the therapist will be present.

• The dosing session. A trained therapist or guide stays with the patient throughout. The patient receives ketamine (often intramuscular, though sublingual and IV routes are also used) and is supported rather than left alone. The therapist may offer gentle verbal guidance, grounding, or simply a steady presence, and music is commonly used to shape the arc of the experience. Conventional talk therapy usually does not happen during the dissociative state itself, but the therapist is there if the patient speaks, becomes distressed, or needs orienting.

• Integration. In one or more follow-up sessions, the patient works with the therapist to make sense of what came up: emotions, images, memories, or shifts in perspective. Integration is widely considered the phase where lasting change takes hold.

Set and setting. The idea that a person’s mindset ("set") and the physical and social environment ("setting") shape a drug experience has deep roots in psychedelic research (Hartogsohn 2017; Carhart-Harris et al. 2018). Most of that work involves classic psychedelics rather than ketamine, but the principle is broadly accepted in the KAP field: a calm, safe space, a trusting relationship with the therapist, and clear intentions can reduce distress and may improve the therapeutic value of a session, while an anxious mindset or a cold, clinical environment can make the dissociative state more disorienting than helpful. A 2025 systematic review (Estric et al.) found that preparation and a safe environment were consistently present in psychedelic-assisted trials, but that these elements are still inconsistently reported and standardized.

Integration practices. Integration usually centers on talk therapy, but it can also include journaling, creative or art-based practices, mindfulness, and body-oriented approaches. The method matters less than the act of making meaning: reflecting on the experience, connecting it to one’s life and goals, and translating insight into concrete change. Many practitioners encourage journaling soon after a session, while impressions are vivid, and at least one integration conversation within a day or two.

What the evidence shows, and what it does not. KAP is widely practiced and has a plausible rationale, and open-label and retrospective studies report encouraging outcomes. Some of the earliest controlled work comes from Krupitsky and colleagues, whose randomized trials of ketamine-assisted psychotherapy for heroin and alcohol dependence found that adding structured psychotherapy improved abstinence at follow-up. Dakwar et al. (2020) paired a single ketamine infusion with motivational enhancement therapy for alcohol use disorder and found less drinking at three weeks compared with a midazolam control.

The rigorous evidence that isolates the psychotherapy component, showing KAP works better than ketamine alone because of the therapy, is limited. A 2026 systematic review (Sabljic et al.) of 72 studies combining ketamine with psychotherapy found that only two had randomized the psychotherapy component itself, and neither reported a statistically significant added effect for the therapy. This does not mean psychotherapy is unimportant; it means the specific question has barely been tested in randomized designs. Its contribution may be real but hard to detect in short trials, may matter more for durability than for acute response, or may depend on the type of therapy. Trials designed to answer this more directly are underway. For now, KAP is a reasonable and widely used approach, grounded in clinical experience and a strong rationale, but patients and clinicians should know that the evidence for the therapy component specifically, as distinct from the drug, is still being built.

Preparing for a Session

Good preparation does not guarantee a good outcome, but it reduces preventable problems and helps you get more from treatment. The advice here applies mainly to in-clinic sessions (IV, IM, or intranasal); for a sublingual or at-home protocol, your provider should give you setting-specific guidance.

Medical screening and honest disclosure. A responsible provider does a thorough medical and psychiatric evaluation before a first session. Be candid about:

• Current medications, especially benzodiazepines (such as alprazolam, lorazepam, clonazepam, or diazepam), which can blunt ketamine’s antidepressant effect by enhancing GABA activity on the same interneurons ketamine acts on. Higher benzodiazepine doses have been associated with a weaker early response. Some providers discuss tapering them first, which must be done gradually and under supervision. Disclose opioids and other sedating medications as well.

• Substance use, including alcohol. Most providers advise no alcohol for at least 24 hours before and after a session. Active substance use disorders are not an absolute bar, but they need careful evaluation.

• Cardiovascular history. Ketamine transiently raises blood pressure and heart rate; uncontrolled hypertension is a strong contraindication, and aneurysmal vascular disease, arteriovenous malformation, or prior intracerebral hemorrhage are contraindications.

• Psychiatric history, especially psychosis or mania. Psychosis and schizophrenia-spectrum disorders are standard exclusions; bipolar disorder calls for monitoring.

• Pregnancy, which is contraindicated based on animal data.

Practical logistics.

• Do not plan to drive. Ketamine impairs coordination and judgment for hours. Arrange a ride or car service; most providers will not release you to drive that day.

• Eating and drinking. A light meal a few hours before, and nothing in the last two hours, is a common guideline, mainly to limit nausea. Stay hydrated, and follow your provider’s specific instructions.

• Clothing. Wear something comfortable and loose; you will be reclined for a while.

• A trusted support person. Having someone to drive you, sit with you, or check in afterward helps. Let a partner, family member, or close friend know your schedule.

• Time afterward. Do not schedule demanding activities for the rest of the day. Many people feel tired, reflective, or emotionally open.

Mindset and intention-setting. “Set” refers to what you bring psychologically: expectations, fears, hopes, and your current state. You do not need a particular mood, but taking a few minutes beforehand to reflect on what you hope for, and what you are willing to be open to, can help orient the experience. Some people write down a simple intention. If you feel anxious, that is normal; tell your provider, who can adjust the pace or offer reassurance.

Planning for integration. Decide in advance how you will process the experience:

• Journaling. Keep a notebook or app handy and capture images, feelings, or fragments within the first few hours, while they are fresh. Patterns often become clearer later.

• A follow-up conversation. In KAP, integration sessions are built in. With infusion-only treatment, consider arranging a session with a therapist or counselor, or even a trusted friend willing to listen.

• Creative practices. Drawing, music, or movement can help process what does not lend itself to words. Optional, but some find it valuable.

• Give it time. Not every session yields a clear insight; effects can be subtle or unfold over days. Resist judging each session immediately.

For the people supporting someone in treatment. If you are a partner, family member, or friend, your role on session day is practical and emotional: help with logistics, then be available afterward without pressing for details. The person may want to talk or may want quiet; let them lead. A few specifics help:

• Session day. Handle the driving, keep the rest of their day unscheduled, and stay reachable.

• Know what is normal and what is not. Tiredness, reflectiveness, and emotional openness are common for the rest of the day. Trouble breathing, or a person who cannot be roused, is an emergency: call 911. Severe or persistent vomiting, or sedation or dissociation that does not lift within a couple of hours, warrants a call to the provider or urgent care. Worsening mood or suicidal thoughts warrant the provider or 988.

• At-home programs put more on you. If the program expects a support person at home, understand what that role involves — and know that your presence is not a substitute for clinical monitoring, which is the core concern behind the FDA’s 2023 warning on compounded at-home ketamine (see Risks, Safety, and Contraindications).

Finding and Evaluating a Provider

Because most information about ketamine therapy comes from the providers who sell it, knowing how to evaluate one matters. A listing in any directory, including those in Resources, is not an endorsement. The questions below apply whether you are considering an in-clinic program or telehealth. For an independent companion to these questions, Harvard Health’s overview of when and where ketamine treatment is safe covers similar ground from a clinic-safety angle.

Credentials and supervision. Confirm who prescribes and who is present during dosing. Look for a licensed clinician (for example, a physician, nurse practitioner, or physician assistant), ideally with psychiatric or anesthesiology experience, and ask what monitoring happens during and after a session. You can check a clinician’s license and any disciplinary history through your state medical board.

Screening. A careful provider takes a real medical and psychiatric history before treating: current medications (especially benzodiazepines, which can blunt the effect), substance-use history, and cardiovascular or psychiatric conditions that change the risk-benefit balance. Minimal screening is a warning sign.

Setting and monitoring. In-clinic care offers on-site monitoring of blood pressure, heart rate, and sedation. Telehealth and at-home models offer convenience and lower cost but less oversight. Ask how the provider handles a difficult reaction or an emergency, and whether someone needs to be with you at home.

Integration and support. Ask whether the program includes preparation and integration (therapy, coaching, or structured follow-up), or only the medication. Integration is much of what distinguishes ketamine-assisted psychotherapy from infusion-only care.

Cost and transparency. Pricing should be clear and itemized. Esketamine (Spravato) is more often covered by insurance; off-label IV or at-home ketamine is usually out of pocket. Be cautious of pressure to prepay for a large package before you know how you respond.

Red flags. Be wary of guaranteed results, aggressive marketing, no medical screening, unclear credentials, no plan for emergencies, or pressure to commit quickly or buy in bulk. Some directories and providers also use affiliate or referral arrangements, so a prominent listing may reflect marketing rather than quality. Johns Hopkins public-health researchers describe how marketing in this market can outrun the evidence.

To find providers, the directories in Resources are a reasonable starting point. Use the questions above to evaluate anyone you find, and verify credentials independently.

Resources

These outside resources can help you find providers and learn more. A listing here is not an endorsement, and you should evaluate any provider independently (see Finding and Evaluating a Provider). Links were last checked on 2026-06-09.

Directories for finding providers

• Ketamine Directory — Free, searchable directory of US ketamine providers, with location filtering and patient reviews.

• Ketamine Clinics Directory — Searchable directory and map of ketamine infusion clinics, mostly US with some international listings.

• HealingMaps — Searchable directory of ketamine clinics with location listings and editorial verification details.

• Ketamine Treatment Resource — Provider directory that also documents providers’ state medical-board infractions and disciplinary history.

• Ketamine Academy Directory — Clinics whose providers completed the Ketamine Academy certification program (graduates only, not all providers).

• Ketamine Saved Me — Patient-oriented provider directory organized by US state.

• Psychedelic.Support — Education platform with a searchable network of KAP-trained practitioners and integration therapists.

Articles and guides

• Innerbody Research — Editorial roundup comparing several online ketamine-therapy platforms.

• Choosing Therapy — Editorial guide on getting a ketamine prescription, online and in person.

If you are in crisis or thinking about harming yourself, do not wait for an appointment. In the US, call or text 988 (Suicide and Crisis Lifeline).

Common Questions and Misconceptions

Is ketamine just a club drug? It is the same molecule in any setting, but the setting matters a great deal. Developed as an anesthetic in the 1960s and approved in 1970, ketamine has been on the WHO Model List of Essential Medicines since 1985 and is still widely used in surgery and emergency care. Therapeutic use means low, sub-anesthetic doses with medical screening, monitoring, and follow-up, which is a different thing from uncontrolled recreational use.

Is ketamine addictive? Ketamine is a Schedule III controlled substance, meaning recognized medical value and a moderate-to-low potential for dependence. The main risk is psychological dependence, tied mostly to frequent or recreational use rather than supervised protocols. Tolerance can develop with repeated exposure, while a physical withdrawal syndrome is not well established. The risk in a structured, screened treatment setting is low, but not zero.

Is the dissociative experience necessary for the benefit? This is genuinely unresolved. Some data show a statistically significant link between the intensity of acute dissociation and the antidepressant response (Luckenbaugh et al. 2014), but the correlation is modest. Meanwhile, work on the metabolite hydroxynorketamine suggests antidepressant-like effects may be possible with little or no dissociation. A 2020 review (Ballard and Zarate) concluded the evidence supports neither a clearly necessary nor a clearly irrelevant role, and researchers remain divided.

How is esketamine (Spravato) different from IV ketamine? Esketamine is the (S)-enantiomer, one half of the racemic mixture used in standard IV infusions. As the nasal spray Spravato, it is the only ketamine formulation with an FDA-approved psychiatric indication (2019), and it must be given in-clinic under a REMS with two hours of monitoring. Racemic IV ketamine is used off-label, is generally less expensive, and in some meta-analyses appears at least as effective.

Is at-home or telehealth ketamine safe? This is actively debated. At-home programs using compounded oral or sublingual ketamine can widen access for people who cannot easily reach a clinic, but they trade away in-person screening, on-site monitoring for cardiovascular or dissociative effects, and control over storage and use. In 2023 the FDA warned about the risks of compounded ketamine used outside healthcare settings, citing serious adverse events. The balance between access and safety remains open.

Is ketamine legal? Yes, when prescribed by a licensed provider and used under appropriate supervision. It has been a Schedule III controlled substance in the United States since 1999, and physicians may prescribe it off-label for psychiatric conditions. Using it without a prescription is illegal.

Does it work for everyone, and is the benefit permanent? No, on both counts. Studies report response rates of roughly 45-70% in treatment-resistant depression, so a real minority do not respond, and the benefit of a single infusion usually fades within one to two weeks. Maintenance or repeated dosing can extend it, but relapse is common after stopping. Ketamine is best understood as one tool within a broader plan, not a one-time cure.

Background: The Science and Evidence

This part traces where ketamine therapy came from and what the research shows: its origins as an anesthetic, the neurobiology behind its rapid antidepressant effects, and the clinical evidence across depression and other conditions.

Early History of Ketamine Therapy

The Unmet Need in Treatment-Resistant Conditions

Modern psychiatry faces a serious challenge in the management of severe and persistent mental health disorders. Conditions such as treatment-resistant depression (TRD), post-traumatic stress disorder (PTSD), obsessive-compulsive disorder (OCD), and chronic anxiety disorders represent a significant public health burden, contributing to substantial personal suffering and escalating disability costs.

For decades, the primary pharmacological strategy has revolved around monoaminergic antidepressants, such as selective serotonin reuptake inhibitors (SSRIs). While beneficial for many, these agents are beset by two critical limitations: a delayed onset of action, often requiring weeks to months to exert a therapeutic effect, and a failure to induce remission in a substantial portion of patients. For major depressive disorder (MDD), as many as one-third of individuals do not respond adequately to multiple conventional treatments, meeting the criteria for TRD.

The high rate of non-response has been described as a “failed experiment” in psychiatric care, where despite an exponential increase in prescribing, the societal costs of mental health disability continue to rise. This clinical impasse has created an urgent need for novel therapeutics with different mechanisms of action and a more rapid onset of efficacy.

The Early Promise of Ketamine Therapy

Ketamine is a drug with a long and varied history. First synthesized in 1962 by the chemist Calvin Stevens at Parke-Davis, ketamine (initially CI-581) was developed as a safer anesthetic alternative to phencyclidine (PCP), which was effective but produced severe, prolonged delirium and neurotoxicity. Ketamine provided effective anesthesia with a more favorable side-effect profile and was approved by the U.S. Food and Drug Administration (FDA) in 1970 under the trade name Ketalar®.6 It became an essential tool in human and veterinary medicine and was used extensively as a battlefield anesthetic during the Vietnam War due to its strong safety profile, particularly its preservation of respiratory drive.

Despite early observations of its mood-altering effects, ketamine’s psychiatric potential remained largely unexplored for nearly three decades. This long delay can be attributed to a few factors:

• The dominant neurobiological model of depression was the monoamine hypothesis, which posits that depression stems from a deficiency in neurotransmitters like serotonin, norepinephrine, and dopamine. Ketamine, a glutamatergic modulator, did not fit this paradigm.

• Furthermore, its dissociative and hallucinogenic properties, which led to its recreational use as a “club drug” and its classification as a Schedule III controlled substance in 1999, were seen as significant liabilities that “undermined its psychiatric utility”.

• With no patent protection, there was little financial incentive for pharmaceutical companies to invest in the rigorous clinical trials needed for a new indication.

The paradigm began to shift only when the limitations of monoaminergic drugs became undeniable. In 1990, researchers at the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), including Phil Skolnick, began investigating alternative systems, leading to the discovery that blocking the N-methyl-D-aspartate (NMDA) glutamate receptor could produce antidepressant-like effects in animal models. This foundational work paved the way for the 2000 study by Berman and colleagues, which provided the first clinical evidence of ketamine’s rapid antidepressant effects in humans.

This discovery overturned long-standing assumptions and shifted the focus of antidepressant research from the monoamine system to the glutamate system, which arguably launched the modern era of ketamine therapy.

The Neurobiology of Ketamine

The therapeutic effects of ketamine are rooted in a complex and multifaceted neurobiological cascade that represents a departure from traditional antidepressant mechanisms. Rather than chronically modulating monoamine levels, sub-anesthetic doses of ketamine act as a catalyst for rapid neuroplasticity.

The Glutamate Hypothesis

Ketamine is a chiral compound, existing as a racemic mixture of two mirror-image enantiomers: (S)-ketamine (esketamine) and (R)-ketamine (arketamine). Its primary and most well-characterized mechanism of action is as a non-competitive antagonist of the N-methyl-D-aspartate (NMDA) receptor, a crucial ionotropic receptor for the excitatory neurotransmitter glutamate. NMDA receptors are tetrameric complexes requiring both glutamate and a co-agonist (glycine or D-serine) to bind, as well as membrane depolarization to expel a magnesium ion (Mg²⁺) that blocks the channel pore at resting potential.

The leading hypothesis for ketamine’s antidepressant action begins with a paradoxical effect. While anesthetic doses decrease glutamate transmission, sub-anesthetic doses are thought to preferentially block NMDA receptors located on inhibitory gamma-aminobutyric acid (GABA)ergic interneurons. These interneurons normally act as “brakes” on excitatory pyramidal neurons. By inhibiting these brakes, ketamine leads to a disinhibition of the pyramidal neurons, resulting in a transient but robust surge of presynaptic glutamate release, particularly within the prefrontal cortex (PFC). This glutamate surge is considered the critical initiating event in the therapeutic cascade, fundamentally altering the brain’s excitatory/inhibitory balance and setting the stage for downstream structural changes.

AMPA, BDNF/TrkB, and mTOR Signaling

The surge in extracellular glutamate does not primarily act on NMDA receptors (which are blocked by ketamine) but instead leads to a widespread activation of another type of glutamate receptor: the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor. This shift in signaling from NMDA to AMPA receptor-mediated activity is central to ketamine’s action and triggers several crucial intracellular signaling pathways that promote neuroplasticity.

Two of the most critical downstream pathways are:

• The BDNF/TrkB Pathway: AMPA receptor activation stimulates the synthesis, release, and signaling of Brain-Derived Neurotrophic Factor (BDNF), a key neurotrophin that regulates neuronal survival, differentiation, and synaptic plasticity. BDNF binds to its high-affinity receptor, Tropomyosin receptor kinase B (TrkB). This interaction is essential for ketamine’s effects; studies in animal models show that blocking BDNF or its receptor negates ketamine’s antidepressant action. Further research indicates that ketamine may also directly bind to the TrkB receptor, facilitating its signaling and further enhancing this pro-plasticity pathway.

• The mTOR Pathway: Both AMPA activation and BDNF-TrkB signaling converge on the mechanistic Target of Rapamycin (mTOR) pathway, a serine/threonine kinase that is a master regulator of cell growth and protein synthesis. Activation of the mTOR complex 1 (mTORC) is critical for synaptogenesis. The necessity of this pathway has been demonstrated in studies where the administration of an mTOR inhibitor, rapamycin, completely blocks the antidepressant effects of ketamine.

Synaptogenesis and Neuroplasticity

Chronic stress and depression are linked to significant neuropathology, particularly in the PFC and hippocampus. These conditions are associated with neuronal atrophy, characterized by a loss of dendritic spines, retraction of dendritic branches, and an overall reduction in synaptic density. This structural decay is thought to be a key substrate of depressive symptomatology.

The signaling cascade initiated by ketamine—from the glutamate surge to AMPA, BDNF, and mTOR activation—directly counteracts this atrophy. By stimulating the synthesis of synaptic proteins, ketamine promotes rapid synaptogenesis: the formation of new synapses and the restoration of lost connections. Remarkably, neuroimaging studies in animal models show that these structural changes, including increases in spine density and dendritic arborization, occur within 24 hours of a single ketamine dose. This rapid “rewiring” of crucial mood-regulating circuits is believed to be the fundamental structural mechanism underlying ketamine’s fast-acting and potent therapeutic effects, effectively reversing the synaptic deficits induced by chronic stress.

Modulating the Default Mode Network (DMN)

Beyond the synaptic level, ketamine exerts substantial effects on large-scale brain networks. In depression, the Default Mode Network (DMN)—a network of brain regions active during rest and involved in self-referential thought, mind-wandering, and rumination—is often found to be hyperactive and hyperconnected. This DMN hyperactivity is thought to be a neural correlate of the persistent, negative, and self-focused rumination common in depression.

Functional neuroimaging studies indicate that ketamine acutely modulates DMN connectivity, typically reducing it, though human findings are heterogeneous. This network-level effect may correspond to the subjective experience of a “reboot” or a temporary break from rigid, negative cognitive patterns that patients often report. By quieting the DMN, ketamine may create a state of increased cognitive flexibility, allowing for the formation of new, more adaptive thought patterns. Ketamine also modulates activity in other key networks, such as the Salience Network (SN) and the Central Executive Network (CEN), further contributing to its complex effects on emotion and cognition.

The Role of Metabolites and Other Receptors

While the NMDA-to-AMPA signaling cascade is the dominant hypothesis, the full story of ketamine’s mechanism is still unfolding and appears to be more complex. A significant challenge to the simple NMDA antagonist theory is that multiple other NMDA-blocking drugs, such as memantine and lanicemine, have failed to produce similarly robust or rapid antidepressant effects in clinical trials. This suggests that NMDA receptor antagonism, while likely necessary, may not be sufficient.

This has led to two important areas of investigation:

• Metabolites: Research from the NIMH has shown that a metabolite of ketamine, (2R,6R)-hydroxynorketamine (HNK), produces antidepressant-like effects in animal models without causing the dissociative side effects associated with the parent drug. Crucially, HNK has much-reduced activity at the NMDA receptor and appears to work primarily by activating AMPA receptors—though whether its effects are genuinely independent of NMDA-receptor activity remains actively debated. This finding has created a central, unresolved tension in the field. It suggests that the antidepressant effects could potentially be separated from the dissociative and psychotomimetic effects, opening the door to developing “non-psychedelic” ketamine-like drugs with a better side-effect profile and lower abuse potential. However, this stands in contrast to other clinical data suggesting that the intensity of dissociative effects during a ketamine infusion correlates with the strength of the antidepressant response. This raises a fundamental question for the future of drug development: is the subjective psychedelic experience a side effect to be engineered out, or is it an integral, perhaps necessary, component of the therapeutic process?

• Other Receptors: Ketamine is not a perfectly “clean” drug and interacts with a variety of other receptor systems. It has been shown to have effects on opioid receptors (though it is not a classic opioid agonist), nicotinic acetylcholine receptors, and monoamine transporters. While its primary action is believed to be glutamatergic, these off-target effects may play a permissive or synergistic role in its overall clinical profile, contributing to its anxiolytic and analgesic properties.

Clinical Efficacy in Treatment-Resistant Depression (TRD)

The most robust and extensive body of clinical evidence for ketamine’s psychiatric use is in the treatment of TRD. The research has progressed systematically from small, initial explorations to large-scale, rigorous trials, establishing ketamine as a legitimate and powerful therapeutic option for this difficult-to-treat population.

Foundational Trials and Their Impact

The modern era of ketamine research was launched by two pivotal studies that provided the initial, compelling evidence for its efficacy.

Berman et al. (2000), Biological Psychiatry: This was the first randomized, placebo-controlled, double-blind crossover study to investigate ketamine for depression. Although the sample size was very small (N=7), its “proof-of-concept” design was rigorous for its time. The study found that a single intravenous (IV) infusion of ketamine at a sub-anesthetic dose of 0.5 mg/kg produced a significant reduction in depressive symptoms (as measured by the Hamilton Depression Rating Scale) within 72 hours, an effect not seen with a saline placebo. The publication of these findings in Biological Psychiatry, a leading psychiatric journal, drew immediate attention from the research community.

Zarate et al. (2006), Archives of General Psychiatry: Building on Berman’s work, this larger (N=18) and more definitive randomized, placebo-controlled, crossover trial from the National Institute of Mental Health (NIMH) solidified ketamine’s potential. The study not only confirmed the rapid antidepressant effects but also quantified their magnitude and duration. It demonstrated a very large effect size (d=1.46) at 24 hours post-infusion, with 71% of TRD patients meeting response criteria and 29% achieving remission. The therapeutic effects began within two hours and remained significant for up to one week. The publication of this robust trial in Archives of General Psychiatry (now JAMA Psychiatry), one of the world’s most influential psychiatry journals (2023 Impact Factor: ~22.5-25.8) 34, was a critical catalyst. It validated the glutamatergic hypothesis of depression and triggered a surge of research that continues today.

Meta-Analyses and Systematic Reviews

Following the foundational trials, a wealth of data has been generated, allowing for comprehensive synthesis. Numerous systematic reviews and meta-analyses have consistently concluded that ketamine produces robust, rapid, and potent antidepressant and anti-suicidal effects in patients with both unipolar and bipolar TRD. A 2022 meta-analysis focusing on real-world clinical data (as opposed to tightly controlled RCTs) found impressive response and remission rates of 45% and 30%, respectively. Importantly, this analysis also found that the therapeutic effect did not appear to diminish with repeated treatments, addressing early concerns about tachyphylaxis (tolerance). A 2023 meta-analysis directly comparing ketamine formulations concluded that racemic ketamine, particularly at higher doses, appears to be more effective and produce longer-lasting effects than its enantiomer, esketamine.

Esketamine (Spravato®)

Recognizing the clinical potential but also the practical barriers of IV ketamine administration (e.g., cost, need for infusion equipment), the pharmaceutical company Janssen developed esketamine, the (S)-enantiomer of ketamine, formulated as an intranasal spray. This formulation, branded as Spravato®, received landmark FDA approval in 2019 for use in conjunction with an oral antidepressant for adults with TRD. Its approval was later expanded to include MDD with acute suicidal ideation or behavior. This was the first new mechanistic class of antidepressant to be approved in decades and was a significant regulatory milestone for the ketamine treatment model.

A key concern has been the long-term safety and efficacy of repeated ketamine administration. The SUSTAIN-3 study, a multi-year, open-label extension trial, provided crucial data on this front. Final results, published in 2024–2025, followed patients for up to 6.5 years and found no new or unexpected long-term safety concerns, including for cognitive function or urinary tract symptoms. The study also demonstrated that the initial antidepressant improvements achieved during induction were generally sustained with long-term, intermittent maintenance dosing, providing confidence in the viability of this treatment approach over extended periods.

Ketamine vs. Electroconvulsive Therapy (ECT)

For decades, electroconvulsive therapy (ECT) has been considered the “gold standard” for the most severe and treatment-resistant forms of depression, due to its high efficacy rates. A critical question for the field was how ketamine would perform in a direct comparison. A landmark 2023 randomized clinical trial led by Anand et al. and published in the prestigious New England Journal of Medicine provided the answer.

This large trial (N=403) directly compared a course of IV ketamine (twice weekly for three weeks) to a course of ECT (three times weekly for three weeks) in patients with non-psychotic TRD. The results showed that ketamine was non-inferior to ECT in terms of antidepressant response. A greater percentage of patients in the ketamine group (55.4%) achieved a response compared to the ECT group (41.2%). Furthermore, ketamine treatment was not associated with the adverse cognitive effects, specifically memory loss, that are a significant drawback of ECT. This trial was an important result for ketamine, establishing it as a viable, and in some respects preferable, alternative to the most powerful existing treatment for severe depression. This finding is likely to significantly influence future clinical practice guidelines and challenge the traditional treatment hierarchy for TRD.

Expanding Indications: PTSD, OCD, and Anxiety Disorders

Building on the success in TRD, research has expanded to investigate ketamine’s efficacy across a spectrum of other difficult-to-treat psychiatric conditions. The evidence in these areas is more nascent and complex, but it points toward distinct potential roles for ketamine in post-traumatic stress disorder, obsessive-compulsive disorder, and anxiety disorders.

Ketamine and Post-Traumatic Stress Disorder (PTSD)

The rationale for using ketamine in PTSD is strong, as the glutamatergic system is fundamentally involved in the neurobiology of fear, stress, and traumatic memory consolidation. The therapeutic hypothesis is that ketamine’s ability to induce synaptogenesis may help restore synaptic connectivity disrupted by trauma, while its dissociative effects might disrupt the fear response and facilitate the reconsolidation of traumatic memories in a less distressing context.

The clinical evidence, however, is mixed. Initial trials were promising. A pioneering 2014 RCT by Feder et al., published in JAMA Psychiatry, was the first to demonstrate that a single IV ketamine infusion led to a rapid and significant reduction in core PTSD symptoms at 24 hours compared to an active placebo (midazolam). A subsequent 2021 study from the same group, published in the American Journal of Psychiatry, found that a course of six repeated infusions was also effective in a predominantly civilian sample with chronic PTSD. More recently, open-label trials combining ketamine with trauma-focused psychotherapy, such as Written Exposure Therapy (WET), have shown potential for large and durable symptom reductions, suggesting a powerful synergistic effect.

Despite these positive signals, the overall evidence base is marked by significant limitations and inconsistencies. A critical finding from a 2023 review in Focus highlighted a potential population-specific effect: while repeated IV ketamine was effective in civilians, it failed to significantly reduce PTSD symptoms in a veteran and military population. This suggests that trauma type or other population characteristics may moderate treatment response. Furthermore, meta-analyses have found that while there is a therapeutic signal, the overall effect size is small and susceptible to publication bias, with larger, more recent studies tending to show weaker effects—a phenomenon known as the “decline effect”. The effects are often transient, and some analyses suggest that the observed benefits may be driven more by ketamine’s potent antidepressant action on comorbid depressive symptoms rather than a direct effect on core PTSD symptoms like intrusion and hyperarousal. Reflecting this uncertainty, a 2023 report from the Canadian Agency for Drugs and Technologies in Health (CADTH) concluded that current evidence does not support the routine use of ketamine for PTSD.

Ketamine and Obsessive-Compulsive Disorder (OCD)

The investigation of ketamine for OCD is also grounded in the glutamate hypothesis, as neuroimaging and cerebrospinal fluid studies have implicated glutamatergic dysfunction in the pathophysiology of the disorder. The first major RCT in this area, conducted by Rodriguez et al. and published in Neuropsychopharmacology in 2013, provided compelling proof-of-concept. This study found that a single IV ketamine infusion produced rapid and significant reductions in obsessive thoughts in drug-free OCD patients. Half of the participants who received ketamine met the criteria for a treatment response (a ≥35% reduction in symptoms on the Yale-Brown Obsessive-Compulsive Scale, or Y-BOCS) one week later. Patients in this and other studies have described a notable, if temporary, state where they “tried to have OCD thoughts, but couldn’t,” suggesting a powerful, acute disruption of obsessional thinking. Recent trials, such as the KET-OCD study (NCT05577585) and a 2025 study in the Journal of Psychopharmacology, continue to build on this foundation, with the latter showing a 60% response rate at 24 hours in the low-dose (0.5 mg/kg) arm following a single intramuscular injection in treatment-resistant OCD—though the higher-dose (1.0 mg/kg) arm did not replicate this, and the effect was short-lived.

The primary limitation, however, is the transient nature of the benefit. Unlike in depression, where effects can be sustained with maintenance dosing, the anti-obsessional effects of ketamine are consistently reported to be short-lived, with symptoms often returning to baseline within one to three weeks post-infusion. This suggests that while ketamine can provide a temporary “vacation from OCD” 54, it is unlikely to be an effective long-term monotherapy. Instead, its primary clinical utility may be as a catalyst to enhance the efficacy of established treatments like exposure and response prevention (ERP) therapy, by creating a temporary window of mental flexibility and reduced symptom burden.

Ketamine and Anxiety Spectrum Disorders (GAD, SAD)

The evidence for ketamine in treating anxiety disorders, such as Generalized Anxiety Disorder (GAD) and Social Anxiety Disorder (SAD), is emerging and appears broadly positive. A key theme in this area is ketamine’s “transdiagnostic” efficacy—its ability to reduce anxiety symptoms across different diagnostic categories.

Multiple systematic reviews and meta-analyses published between 2022 and 2023 have synthesized the data from various RCTs and concluded that ketamine produces significant and rapid anxiolytic effects. These effects are apparent within hours of administration (within 12 hours) and are sustained for at least one to two weeks. An early study from 2017 demonstrated that a course of weekly ketamine treatments was effective for both GAD and SAD. A key nuance, however, is the confounding effect of depression. Meta-analyses have found a strong correlation between improvements in anxiety and depression scores. This raises a crucial question: is ketamine a primary anxiolytic, or does it primarily treat comorbid depression, with anxiety reduction being a secondary benefit? While the answer is not yet definitive, the evidence suggests that its potent antidepressant action is at least a major contributor to its observed anxiolytic effects. This reframes its potential role not as a replacement for traditional anxiolytics, but as a powerful tool for patients with severe, treatment-resistant anxiety, particularly when it co-occurs with depression.

The collective evidence across PTSD, OCD, and anxiety disorders points to a nuanced role for ketamine. For TRD, it stands as a primary biological intervention. For these other conditions, its utility appears to lie in its ability to act as a pharmacological catalyst. By rapidly reducing depressive comorbidity and inducing a temporary state of enhanced neuroplasticity and reduced defensive processing, ketamine creates a “window of opportunity” for patients to engage more deeply and effectively with psychotherapies that are essential for achieving durable, long-term change. This positions Ketamine-Assisted Psychotherapy (KAP) not merely as an alternative, but potentially as the optimal modality for harnessing ketamine’s benefits in these complex disorders.

Table 1: Landmark Clinical Trials of Ketamine for Mental Health Disorders

References

History and pharmacology

• Li L, Vlisides PE. Ketamine: 50 Years of Modulating the Mind. Front Hum Neurosci. 2016;10:612. PMID: 27965560; PMCID: PMC5126726. Full text (Corrected: the draft mis-attributed this review to Domino EF / Front Neuroanat.)
• Lodge D, Mercier MS. Ketamine and phencyclidine: the good, the bad and the unexpected. Br J Pharmacol. 2015;172(17):4254–4276. PMID: 25771987; PMCID: PMC4556466. Full text
• Trullas R, Skolnick P. Functional antagonists at the NMDA receptor complex exhibit antidepressant actions. Eur J Pharmacol. 1990;185(1):1–10. PMID: 2171955. (NIDDK; foundational NMDA-antidepressant work.) DOI

Foundational trials in depression (TRD)

• Berman RM, Cappiello A, Anand A, et al. Antidepressant effects of ketamine in depressed patients. Biol Psychiatry. 2000;47(4):351–354. PMID: 10686270. DOI
• Zarate CA Jr, Singh JB, Carlson PJ, et al. A randomized trial of an N-methyl-D-aspartate antagonist in treatment-resistant major depression. Arch Gen Psychiatry. 2006;63(8):856–864. PMID: 16894061. DOI
• Murrough JW, Iosifescu DV, Chang LC, et al. Antidepressant efficacy of ketamine in treatment-resistant major depression: a two-site randomized controlled trial. Am J Psychiatry. 2013;170(10):1134–1142. PMID: 23982301; PMCID: PMC3992936. Full text

Neurobiology and mechanism

• Zanos P, Moaddel R, Morris PJ, et al. Ketamine and ketamine metabolite pharmacology: insights into therapeutic mechanisms. Pharmacol Rev. 2018;70(3):621–660. PMID: 29945898; PMCID: PMC6020109. Full text
• Paoletti P, Bellone C, Zhou Q. NMDA receptor subunit diversity. Nat Rev Neurosci. 2013;14(6):383–400. PMID: 23686171. DOI
• Moghaddam B, Adams B, Verma A, Daly D. Activation of glutamatergic neurotransmission by ketamine. J Neurosci. 1997;17(8):2921–2927. PMID: 9092613. Full text
• Homayoun H, Moghaddam B. NMDA receptor hypofunction produces opposite effects on prefrontal cortex interneurons and pyramidal neurons. J Neurosci. 2007;27(43):11496–11500. PMID: 17959792; PMCID: PMC2954603. Full text
• Gerhard DM, Pothula S, Liu RJ, et al. GABA interneurons are the cellular trigger for ketamine’s rapid antidepressant actions. J Clin Invest. 2020;130(3):1336–1349. PMID: 31743111; PMCID: PMC7269589. Full text
• Maeng S, Zarate CA Jr, et al. Cellular mechanisms underlying the antidepressant effects of ketamine: role of AMPA receptors. Biol Psychiatry. 2008;63(4):349–352. PMID: 17643398. DOI
• Li N, Lee B, Liu RJ, et al. mTOR-dependent synapse formation underlies the rapid antidepressant effects of NMDA antagonists. Science. 2010;329(5994):959–964. PMID: 20724638; PMCID: PMC3116441. Full text
• Autry AE, Adachi M, Nosyreva E, et al. NMDA receptor blockade at rest triggers rapid behavioural antidepressant responses. Nature. 2011;475(7354):91–95. PMID: 21677641; PMCID: PMC3172695. Full text
• Casarotto PC, Girych M, Fred SM, et al. Antidepressant drugs act by directly binding to TRKB neurotrophin receptors. Cell. 2021;184(5):1299–1313. PMID: 33606976; PMCID: PMC7938888. (Direct-TrkB-binding hypothesis; not yet broadly replicated.) Full text
• Moda-Sava RN, Murdock MH, Parekh PK, et al. Sustained rescue of prefrontal circuit dysfunction by antidepressant-induced spine formation. Science. 2019;364(6436):eaat8078. PMID: 30975859; PMCID: PMC6785189. Full text
• Scheidegger M, Walter M, Lehmann M, et al. Ketamine decreases resting state functional network connectivity in healthy subjects. PLoS One. 2012;7(9):e44799. PMID: 23049758; PMCID: PMC3461985. Full text
• Greicius MD, Flores BH, Menon V, et al. Resting-state functional connectivity in major depression. Biol Psychiatry. 2007;62(5):429–437. PMID: 17210143; PMCID: PMC2001244. Full text
• Zanos P, Moaddel R, Morris PJ, et al. NMDAR inhibition-independent antidepressant actions of ketamine metabolites. Nature. 2016;533(7604):481–486. PMID: 27144355; PMCID: PMC4922311. (Original (2R,6R)-HNK finding.) Full text
• Suzuki K, Nosyreva E, Hunt KW, Kavalali ET, Monteggia LM. Effects of a ketamine metabolite on synaptic NMDAR function. Nature. 2017;546(7659):E1–E3. PMID: 28640258. (Disputes HNK’s NMDAR-independence.) DOI
• Aleksandrova LR, Wang YT, Phillips AG. Hydroxynorketamine: implications for the NMDA receptor hypothesis of ketamine’s antidepressant action. Chronic Stress. 2017;1. PMID: 30556028; PMCID: PMC6292673. Full text
• Newport DJ, Carpenter LL, McDonald WM, et al. Ketamine and other NMDA antagonists: early clinical trials and possible mechanisms in depression. Am J Psychiatry. 2015;172(10):950–966. PMID: 26423481. DOI
• Sanacora G, Johnson MR, Khan A, et al. Adjunctive lanicemine (AZD6765) in patients with MDD and inadequate antidepressant response. Neuropsychopharmacology. 2017;42(4):844–853. PMID: 27681442; PMCID: PMC5312066. Full text
• Luckenbaugh DA, Niciu MJ, Ionescu DF, et al. Do the dissociative side effects of ketamine mediate its antidepressant effects? J Affect Disord. 2014;159:56–61. PMID: 24679390; PMCID: PMC4065787. Full text
• Ballard ED, Zarate CA. The role of dissociation in ketamine’s antidepressant effects. Nat Commun. 2020;11:6431. PMID: 33353946; PMCID: PMC7755908. Full text

Meta-analyses and esketamine (Spravato)

• Alnefeesi Y, Chen-Li D, Krane E, et al. Real-world effectiveness of ketamine in treatment-resistant depression: a systematic review & meta-analysis. J Psychiatr Res. 2022;151:693–709. PMID: 35688035. DOI
• Nikolin S, Rodgers A, Schwaab A, et al. Ketamine for the treatment of major depression: a systematic review and meta-analysis. eClinicalMedicine. 2023;62:102127. PMID: 37593223; PMCID: PMC10430179. Full text
• Zaki N, Chen LN, Lane R, et al. Long-term safety and maintenance of response with esketamine nasal spray in participants with treatment-resistant depression: interim results of the SUSTAIN-3 study. Neuropsychopharmacology. 2023;48(8):1225–1233. PMID: 37173512; PMCID: PMC10267177. Full text (Corrected: the draft listed Wajs E as first author; this paper is first-authored by Zaki N and Wajs E is not an author — confirmed against PubMed/PMC.)
• Zaki N, Chen LN, Lane R, et al. Safety and efficacy with esketamine in treatment-resistant depression: long-term extension study (SUSTAIN-3). Int J Neuropsychopharmacol. 2025;28(6):pyaf027. PMID: 40319349; PMCID: PMC12143125. Full text

Ketamine vs. ECT

• Anand A, Mathew SJ, Sanacora G, et al. Ketamine versus ECT for nonpsychotic treatment-resistant major depression. N Engl J Med. 2023;388(25):2315–2325. PMID: 37224232. DOI

PTSD

• Feder A, Parides MK, Murrough JW, et al. Efficacy of intravenous ketamine for treatment of chronic PTSD: a randomized clinical trial. JAMA Psychiatry. 2014;71(6):681–688. PMID: 24740528. DOI
• Feder A, Costi S, Rutter SB, et al. A randomized controlled trial of repeated ketamine administration for chronic PTSD. Am J Psychiatry. 2021;178(2):193–202. PMID: 33397139; PMCID: PMC10316213. Full text
• Norbury A, Rutter SB, Collins AB, et al. Ketamine for treatment of PTSD: state of the field. Focus (Am Psychiatr Publ). 2023;21(3):257–265. PMID: 37404968; PMCID: PMC10316217. Full text (Corrected page range: 257–265, not 239–249.)
• CADTH (CDA-AMC). Ketamine for adults with treatment-resistant depression or PTSD: a 2023 update. Rapid Review. NCBI Bookshelf NBK602384; PMID: 38564542. Full text

OCD

• Rodriguez CI, Kegeles LS, Levinson A, et al. Randomized controlled crossover trial of ketamine in OCD: proof-of-concept. Neuropsychopharmacology. 2013;38(12):2475–2483. PMID: 23783065; PMCID: PMC3799067. Full text
• Beaglehole B, Glue P, Neehoff S, et al. Ketamine for treatment-resistant obsessive-compulsive disorder: double-blind active-controlled crossover study. J Psychopharmacol. 2025;39(1):23–28. PMID: 39609659; PMCID: PMC11760645. Full text
• KET-OCD trial. ClinicalTrials.gov NCT05577585 (Medical University of Vienna; IV ketamine crossover). ClinicalTrials.gov

Anxiety (GAD/SAD)

• Hartland H, Mahdavi K, Jelen LA, et al. A transdiagnostic systematic review and meta-analysis of ketamine’s anxiolytic effects. J Psychopharmacol. 2023;37(8):764–774. PMID: 37005739; PMCID: PMC11921208. Full text
• Tully JL, Dahlén AD, Haggarty CJ, et al. Ketamine treatment for refractory anxiety: a systematic review. Br J Clin Pharmacol. 2022;88(10):4412–4426. PMID: 35510346; PMCID: PMC9540337. Full text
• Glue P, Medlicott NJ, Harland S, et al. Ketamine’s dose-related effects on anxiety symptoms in patients with treatment-refractory anxiety disorders. J Psychopharmacol. 2017;31(10):1302–1305. PMID: 28441895. DOI
• Loo C, et al. Ketamine for Adult Depression Study (KADS). Br J Psychiatry. 2023;223(6):533–541. PMID: 38108319; PMCID: PMC10727911. Full text
  • ⚠ RETRACTED — anxiety secondary analysis: Mills NT, et al. Effect of ketamine on anxiety: findings from the Ketamine for Adult Depression Study. Br J Psychiatry. 2025;227(3):601–607. PMID: 39763417. Retracted March 2026 (retraction notice PMID 41913440). The guide no longer cites this paper as support; this entry is kept to document the retraction.

Practical, safety, and regulatory sources

Added for the practical sections above. Pending the same primary-source verification as the rest of this list (kg-dott).

• Sanacora G, Frye MA, McDonald W, et al. A consensus statement on the use of ketamine in the treatment of mood disorders. JAMA Psychiatry. 2017;74(4):399–405. PMID: 28249076.

• McIntyre RS, Rosenblat JD, Nemeroff CB, et al. Synthesizing the evidence for ketamine and esketamine in treatment-resistant depression: an international expert opinion. Am J Psychiatry. 2021;178(5):383–399. PMID: 33726522.

• Murrough JW, Perez AM, Pillemer S, et al. Rapid and longer-term antidepressant effects of repeated ketamine infusions in treatment-resistant major depression. Biol Psychiatry. 2013;74(4):250–256. PMID: 23206963.

• Anderson DJ, Zhou J, Cao D, et al. Ketamine-induced cystitis: a review of the urologic effects. Health Psychol Res. 2022;10(3):38247. PMID: 36118982.

• Kerr-Gaffney J, et al. Urological symptoms following ketamine treatment for psychiatric disorders: a systematic review. J Psychopharmacol. 2025. PMID: 40583492.

• Chang M, Juruena MF, Young AH. Ketamine cystitis following ketamine therapy for treatment-resistant depression: a case report. BMC Psychiatry. 2024;24:9. PMID: 38166893.

• Ketamine pharmacology: an update (bioavailability by route). CNS Neurosci Ther. 2019;25(4):515–527. PMCID: PMC6493357.

• Yanagihara Y, et al. Absolute bioavailability of ketamine from a sublingual formulation. Br J Clin Pharmacol. 2003;55(6):573–576. PMCID: PMC4093926.

• U.S. FDA. Spravato (esketamine) prescribing information and approval history (TRD 2019; depressive symptoms with suicidal ideation 2020; monotherapy for TRD 2025). FDA label

• U.S. FDA. Ketalar (ketamine) prescribing information (initial U.S. approval 1970). FDA label

• U.S. FDA. Risks associated with compounded ketamine products for psychiatric disorders (safety communication). 2023. FDA

• DEA. Placement of ketamine into Schedule III. Federal Register. 1999;64:37673. Federal Register

• WHO Model List of Essential Medicines (ketamine). WHO

• Hartogsohn I. Constructing drug effects: a history of set and setting. Drug Sci Policy Law. 2017;3. DOI

• Carhart-Harris RL, Roseman L, Haijen E, et al. Psychedelics and the essential importance of context. J Psychopharmacol. 2018;32(7):725–731. PMID: 29446697.

• Estric C, Duron T, Kabani S, Lopez-Castroman J. Set and setting of psychedelics for therapeutic use in psychiatry: a systematic review. J Psychopharmacol. 2025. PMID: 40353492.

• Krupitsky EM, et al. Single versus repeated sessions of ketamine-assisted psychotherapy for heroin dependence. J Psychoactive Drugs. 2007;39(1):13–19. PMID: 17523581.

• Dakwar E, Levin F, Hart CL, et al. A single ketamine infusion combined with motivational enhancement therapy for alcohol use disorder: a randomized, midazolam-controlled pilot trial. Am J Psychiatry. 2020;177(2):125–133. PMID: 31786934.

• Sabljic A, et al. Ketamine-assisted psychotherapies for mental disorders: a historical overview and systematic review. Clin Psychol Rev. 2026;105:102525.

• Kew BM, Porter RJ, Douglas KM, et al. Ketamine and psychotherapy for the treatment of psychiatric disorders: a systematic review. BJPsych Open. 2023;9(3):e79. PMCID: PMC10228275.

Disclaimer

This guide is for informational and educational purposes only. It is not medical advice, and it is not a substitute for diagnosis, treatment, or guidance from a qualified healthcare professional. Nothing here should be taken as a recommendation to obtain, use, or self-administer ketamine or any other substance.

Ketamine is a Schedule III controlled substance in the United States. It is legal only when prescribed and administered under appropriate medical supervision. Outside of a supervised clinical setting, use carries serious risks—including dissociation and impaired judgment, accidents, nausea and vomiting, dangerous interactions with other drugs (especially alcohol, benzodiazepines, and opioids), elevated blood pressure and heart rate, bladder and urinary-tract damage with repeated use, and the potential for psychological dependence. Ketamine should never be used while pregnant, and people with a history of psychosis, uncontrolled hypertension, or certain cardiac conditions face heightened risk.

The therapeutic effects described in this guide were generally observed in controlled clinical trials with medical screening, monitoring, and integration support. Outcomes in those settings do not predict the safety of unsupervised use.

If you are considering ketamine therapy, consult a licensed physician or mental-health provider. If you are in crisis or thinking about harming yourself, contact emergency services immediately. In the U.S., call or text 988 (Suicide and Crisis Lifeline).