How Long Does Ketamine Therapy Last for Depression?

In trials, often within hours. In a 2006 placebo-controlled trial of adults with treatment-resistant depression, people given a single intravenous dose improved more than those given placebo within about two hours. In a 2013 study of repeated infusions, depression scores dropped sharply two hours after the first one.

That speed is the reason ketamine drew so much research attention. Typical antidepressants can take several weeks to act, a delay the 2006 authors described as causing considerable illness while people wait. Speed of onset, though, says nothing about how long the improvement will last.

Usually days, not months. In the 2006 trial, the advantage over placebo was still significant a week after the dose, but only about a third of the people treated still met the study's response criteria at that point. A 2020 meta-analysis of randomized trials found the largest effect at 24 hours, with a measurable difference lasting up to seven days after a single dose.

A Cochrane review published in 2021 rated the evidence comparing ketamine with placebo at 24 hours as very low certainty, partly because many trials gave too little detail about how treatment assignment was kept hidden from participants and raters.

In the studies so far, often weeks rather than months once sessions stop. Three studies give a sense of the pattern:

Possibly, for some people, but the evidence is thin. In a 2019 randomized trial, participants who responded to six infusions moved on to four weekly sessions, and their symptom scores did not change during that phase. The KADS authors concluded that benefits fade after treatment stops for most patients and that ketamine should be considered as a longer-term treatment.

What nobody can yet say is how long maintenance should continue, how far apart sessions can be spaced, or what longer use means for safety. Experts convened by the American Psychiatric Association flagged how little longer-term evidence exists, and a 2018 review found that safety after repeated or long-term use had barely been assessed.

Because durability differs so much between people, nothing about your result is assumed in advance. Typical plans here involve a series of sessions over several weeks, then a reassessment of how you have responded. Depending on that, the plan can continue, sessions can be spaced out, or treatment can stop.

It also helps to keep the rest of your care in place. If you agree, we keep your existing psychiatrist, therapist, or physician informed, so the people already caring for you can see how you are doing between sessions.

Returning symptoms are common in the research and worth reporting early, not something to push through alone. Contact the clinic during office hours at (656) 269-4567, Monday to Friday, 9am to 5pm. If you are having thoughts of suicide or feel unsafe, call or text 988 to reach the Suicide & Crisis Lifeline at any hour, or call 911 for an emergency.