Patients often ask how a medication best known as an anesthetic ends up easing depression that hasn't budged for years. It's a fair question, and the honest answer is that ketamine works in a fundamentally different way than the antidepressants most people have already tried. Understanding that difference helps explain why the treatment can act so quickly, and why the work you do in the weeks afterward matters as much as the infusion itself.
A different target than standard antidepressants
Most common antidepressants, the SSRIs and SNRIs, act on serotonin and norepinephrine, and they typically take four to six weeks to show an effect. Ketamine doesn't work that way. It acts mainly on the glutamate system, the brain's most abundant excitatory signaling network. By blocking a receptor called the NMDA receptor, ketamine sets off a cascade that increases glutamate signaling in a controlled way and, downstream, raises levels of a protein called brain-derived neurotrophic factor (BDNF). It helps explain why relief can arrive within hours or days rather than weeks.
BDNF and the growth of new connections
BDNF is sometimes described as fertilizer for the brain, and the metaphor holds up reasonably well. It supports the growth and strengthening of synapses, the connection points between neurons. Researchers at Yale, including Ronald Duman and John Krystal, showed that ketamine can rapidly promote new synaptic connections in brain regions that tend to atrophy under chronic stress and depression. In practical terms, the brain becomes briefly more able to form new patterns instead of running the same worn grooves. That capacity to change is what we mean when we talk about neuroplasticity.
Clearing up a common misconception
Let's clear up something patients often get backwards. Ketamine isn't working because you have a fun or unusual experience during the infusion. The dissociative feeling some people notice is a side effect of the dose, not the mechanism of benefit. The antidepressant effect comes from the glutamate cascade and the synaptic changes that follow, and those happen whether or not the session felt remarkable. Patients sometimes worry that a quiet, uneventful infusion means it isn't working. The opposite is closer to the truth. A calm session your body settles into is exactly the kind we're aiming for, and the meaningful changes tend to show up in the days afterward rather than in the chair.
The window is real, and it's temporary
Here's the part that gets lost in the excitement about mechanism. The heightened neuroplasticity ketamine produces doesn't last indefinitely. It opens a window, often described as lasting days to a couple of weeks after an infusion, during which the brain is unusually receptive to forming new connections. The infusion doesn't install a new mood. It creates a period in which change is more possible than usual. What you do with that period has a lot to say about whether the benefit holds.
Ketamine loosens the rigid patterns. Integration is how you use that opening before it closes.
Why integration matters
This is why we treat the session and the days that follow as one continuous treatment rather than two separate things. During the open window, the small choices compound. Gentle movement, better sleep habits, time with people you trust, therapy if you have it, and simply noticing and building on the moments that got easier. We coordinate with your own therapist when you have one, and we can refer you into our network if you don't. None of this is mystical. It's the ordinary work of laying down healthier patterns at the one time the brain is most ready to lay them down.
Why a series, and not a single dose
If one infusion can open the window, patients reasonably ask why we recommend a series at all. The answer is that a single dose tends to produce a brief effect, while a course of infusions, commonly six over two to three weeks, produces a sturdier and longer-lasting response for most people. Each session reopens and extends the period of heightened plasticity, and the repeated experience gives the new patterns time to take hold rather than fade. Think of it less as six separate treatments and more as one treatment delivered in stages. After the initial series, some patients do well with occasional maintenance infusions, spaced weeks or months apart, and we decide that together based on how you actually respond rather than a fixed schedule.
What the evidence does and doesn't say
The science here is genuinely promising and still developing. The rapid antidepressant effect has been replicated across many controlled trials since the first study by Berman and colleagues in 2000, and the FDA's approval of esketamine (Spravato) for treatment-resistant depression in 2019 reflects how seriously the mechanism is now taken. That said, IV ketamine for mood conditions remains an off-label use, response varies between people, and durability is exactly why the integration work exists. We'll always be straight with you about what's well established and what we're still learning.
If you want to talk through whether this fits your history and what a full series would look like, you can book a consultation. We'll go over the science, the schedule, and the integration plan together, in plain language.