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Ketamine can rapidly reduce severe depression, hopelessness, and suicidal thinking.

Repeated ketamine use can cause addiction, cognitive impairment, and potentially irreversible bladder damage.

The challenge is preserving ketamine’s therapeutic value while preventing misuse and reducing harm.

In the morning, a psychiatrist administers ketamine to help a suicidal patient rediscover hope. That evening, an emergency physician treats someone whose recreational ketamine use contributed to an accident, overdose, or dangerous drug combination. The same drug. Two very different stories. A treatment moves from the laboratory to carefully selected patients, and then, use expands. Then consequences emerge—not apparent or measurable—at the beginning.

The National Drug Early Warning System rang an alarm bell on July 17, 2026. NDEWS identified 71,924 nonfatal EMS encounters involving suspected ketamine overdoses nationwide between January 2023 and June 2026.

These data are alarming, but surveillance cannot establish illicit versus prescribed. Nevertheless, this is a public health signal that addiction medicine cannot ignore.

A New Way of Thinking About Depression

For 50 years, ketamine has been an anesthetic in surgery, trauma care, and battlefield medicine. What changed was the question scientists asked. That question belonged to a Yale bench-to-bedside tradition I knew well. I worked with George Aghajanian, where LSD was studied not as a curiosity but as an instrument to gain insight into serotonin and the brain. George helped demonstrate that noradrenergic neurons become hyperactive during opioid withdrawal and that clonidine could suppress them. I helped carry those insights from rats into nonhuman primates and later human patients, establishing clonidine as the first non-opioid treatment for opioid withdrawal.

Ketamine grew from the Yale Psychiatry research culture that asked what an unusual drug might teach us about the brain. Decades later, Aghajanian’s research helped connect serotonin, glutamate, cortical plasticity, and rapid-acting antidepressant effects.

In 2000, John Krystal and his Yale colleagues reported that a subanesthetic ketamine dose could rapidly reduce major depression. Patients with treatment-resistant depression, hopelessness, or suicidal thinking sometimes improved within hours rather than weeks. Ketamine can save lives.

Ketamine also changed how we think about depression. Although it blocks NMDA receptors, no single receptor explains everything. It affects glutamate signaling, reward responsiveness, and cortical plasticity, perhaps loosening rigid brain activity and creating an opportunity for new learning.

A July 2026 Molecular Psychiatry study expands the story beyond glutamate. Investigators compared ketamine, its metabolite hydroxynorketamine, LSD, and psilocybin. Despite acting initially through different receptors, these rapid-acting antidepressants apparently converged on downstream neuroimmune pathways, particularly IL-7 and IL-15 signaling. Some biological signatures also distinguished ketamine responders from nonresponders.

These preliminary findings show why ketamine and psychedelics should be studied neither as miracle drugs nor solely as intoxicants. They may teach us how depression becomes entrenched—and reversed. That is also where ketamine treatment and ketamine addiction begin to intersect.

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