Ketamine for Treatment-Resistant Depression

Understanding Treatment-Resistant Depression

Treatment-resistant depression (TRD) is generally defined as major depressive disorder (MDD) that has not responded adequately to at least two different antidepressant medications taken at appropriate doses for sufficient durations. By this definition, approximately one-third of the 280 million people worldwide who suffer from depression are considered treatment-resistant.

TRD represents one of the greatest unmet needs in mental healthcare. Patients with TRD experience prolonged suffering, impaired functioning, higher rates of hospitalization, increased healthcare costs, and elevated risk of suicide. For these individuals, ketamine therapy has emerged as one of the most significant treatment advances in decades. To understand the science behind this breakthrough, see our guide on how ketamine works in the brain.

The Clinical Evidence

The evidence supporting ketamine for TRD is substantial and growing. Since the initial Yale study in 2000 and the confirmatory NIMH trial in 2006, hundreds of clinical studies have evaluated ketamine's antidepressant effects.

Key Findings

• Rapid onset — Antidepressant effects are typically observed within 2 to 4 hours after a single intravenous infusion, with peak effects at 24 hours.
• High response rates — Meta-analyses suggest that approximately 60-70% of TRD patients show significant improvement after a series of ketamine infusions.
• Anti-suicidal effects — Ketamine has demonstrated rapid reduction in suicidal ideation, often within hours. This is particularly significant, as most conventional antidepressants carry an initial period of increased suicide risk.
• Efficacy across subtypes — Ketamine has shown effectiveness in unipolar depression, bipolar depression, depression with anxiety, and depression with anhedonia (inability to feel pleasure).

How Ketamine Treatment Works for Depression

IV Infusion Protocol

The most studied protocol for depression involves a series of six intravenous infusions over two to three weeks. Each infusion delivers ketamine at a sub-anesthetic dose of 0.5 mg/kg over 40 minutes. Patients are awake during the infusion and may experience mild dissociative effects, changes in perception, and temporary increases in blood pressure.

After the initial series, maintenance infusions are typically scheduled based on individual response — often ranging from once every two weeks to once a month. Some patients experience sustained remission after the initial series and require only occasional booster infusions.

Esketamine (Spravato) Protocol

FDA-approved esketamine nasal spray follows a specific dosing schedule. Treatment begins with sessions twice per week for the first month, followed by once weekly for the second month, and then once weekly or every two weeks thereafter. Each session is conducted in a certified healthcare setting with a two-hour post-dose monitoring period.

What Patients Experience

During a ketamine infusion for depression, patients typically experience a range of effects that resolve within one to two hours:

• A floating or detached sensation
• Mild visual distortions or enhanced colors
• Altered sense of time
• A dream-like state
• Feelings of calm or emotional release
• Temporary increases in blood pressure and heart rate

Many patients describe the experience as introspective and sometimes emotionally meaningful. Some clinicians integrate brief psychotherapy before or after infusions to help patients process the experience and reinforce therapeutic insights.

Who Is a Good Candidate

Ketamine therapy for depression is typically considered for patients who:

• Have been diagnosed with major depressive disorder
• Have not responded to at least two adequate trials of conventional antidepressants
• Are not actively experiencing psychotic symptoms
• Do not have uncontrolled hypertension
• Do not have a history of substance use disorder involving ketamine or similar substances
• Are willing to commit to the treatment schedule and monitoring requirements

Potential Risks and Side Effects

Like all medical treatments, ketamine carries risks that must be weighed against potential benefits:

• Short-term side effects — Nausea, dizziness, elevated blood pressure, dissociation, and blurred vision are common during and shortly after infusions but typically resolve quickly.
• Cognitive effects — Some patients report transient difficulties with memory or concentration in the hours following treatment.
• Abuse potential — As a Schedule III controlled substance, ketamine carries a risk of dependence, though this risk is considered low when used under medical supervision at prescribed doses.
• Urological concerns — Long-term, high-dose recreational use has been associated with bladder damage, but this has not been observed at the doses and frequencies used in clinical treatment.

The Importance of Comprehensive Care

Ketamine is most effective when integrated into a comprehensive treatment plan. For more about how ketamine works in the brain, including the neuroplasticity mechanisms that underlie its effects, see our detailed guides. This typically includes ongoing psychotherapy, medication management, lifestyle modifications (exercise, sleep hygiene, nutrition), and social support. Ketamine should not be viewed as a standalone cure but rather as a powerful tool that can create a window of neuroplasticity and symptom relief during which other therapeutic interventions become more effective.

Important: If you or someone you know is experiencing thoughts of self-harm, contact the 988 Suicide and Crisis Lifeline by calling or texting 988.

References

• NIMH: Depression — National Institute of Mental Health overview of depression, including treatment-resistant forms and emerging treatments
• WHO: Depression Fact Sheet — World Health Organization global information on depression prevalence and treatment
• StatPearls: Ketamine — Comprehensive clinical reference on ketamine's use in treatment-resistant depression
• MedlinePlus: Esketamine Nasal Spray — Drug information on FDA-approved Spravato (esketamine) for treatment-resistant depression
• 988 Suicide and Crisis Lifeline — National crisis intervention resource for individuals experiencing suicidal thoughts