Ketamine: Benefits and Risks for Depression, PTSD & Neuroplasticity | Huberman Lab Podcast
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- ~4 min
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- 7 Aug 2023
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- 1:42:40
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KEYPOINTS
- 01
Ketamine is a close cousin of PCP with real clinical value and real abuse potential
Both are dissociative anesthetics that block the NMDA receptor. Huberman says ketamine has proven 'miraculous' for some people, though not all, when used clinically for depression, suicidality and PTSD. It also has high abuse potential, and he notes that wider legal access, including take-home prescriptions, has brought more recreational use and some addiction.
- 02
Standard antidepressants leave a large gap
Drugs built on the monoamine hypothesis, such as SSRIs and bupropion, give true relief to only about 40% of depressed people. Benefits often take weeks or months to appear, and side effects (appetite and sleep changes, sharply reduced libido) make them intolerable for some. Huberman stresses these drugs have still helped many people and prevented suicides.
- 03
Ketamine works within hours, but the effect is short-lived
Relief can come the same day, even in people unresponsive to SSRIs, and can reduce suicidality, helplessness and worthlessness. Clinical studies also support uses in bipolar depression, PTSD, OCD, anxiety and substance addiction. The antidepressant effect often fades after about three days to a week, and weekly dissociative sessions aren't practical for many people.
- 04
It boosts plasticity by disinhibition
Ketamine blocks NMDA receptors on inhibitory neurons, which releases the brakes on excitatory neurons in mood and reward circuits. These neurons then fire in bursts, the pattern that best induces lasting changes. Bursting triggers BDNF release; BDNF binds TrkB receptors, adds glutamate (AMPA) receptors and grows new branches on neurons. Pre-clinical and clinical evidence suggests BDNF may actually be required for ketamine's antidepressant effect.
- 05
The opioid system appears necessary for the antidepressant effect
Ketamine binds mu and kappa opioid receptors, and its metabolite hydroxynorketamine (HNK) is highly selective for them. In a study by Stanford's Nolan Williams, Alan Schatzberg and colleagues, blocking opioid receptors with naltrexone left ketamine's euphoria and dissociation intact but abolished its antidepressant and anti-suicidal effects. Several studies support this.
- 06
The 'trip' and the therapeutic benefit may be separate
From the naltrexone result, Huberman draws a broader point for ketamine, psilocybin and MDMA. The acute subjective experience may not be what produces long-term relief. He doubts it's strictly either/or, but cautions against assuming the intensity of the experience predicts the benefit.
- 07
Ketamine quiets the brain's 'disappointment' circuit
The habenula inhibits the dopamine reward pathway (VTA and nucleus accumbens), reducing dopamine and raising cortisol; bright light in the middle of the night activates it. Ketamine therapy appears to lessen the habenula's inhibitory output, making the reward pathway more available.
- 08
Behavior determines whether the window of plasticity helps
Circuit changes do little unless daily life reinforces them. If someone keeps up pro-depressive patterns, ketamine provides little relief. Seeking stimulating work, social engagement and good physical and mental self-care are the 'anti-depressive behaviors' that make the opened window count.
EXAMPLES
- 01
The seven-patient trial that started it
In a small early study, seven people with major depression received IV ketamine at 0.5 mg/kg. Effects began within 10–15 minutes, peaked as a euphoric, dreamy, semi-dissociative state at 45–60 minutes, and the euphoria was over in about two hours. Depression relief came within minutes to hours and lasted at least three days, well beyond the drug's acute effects. This made ketamine especially attractive for depression that hadn't responded to other treatments.
- 02
Twice weekly for three weeks
Later clinical studies gave ketamine twice a week for three weeks. Patients had relief throughout, and many kept some benefit for months afterward before needing to repeat the course. Huberman attributes this durability to genuine circuit rewiring.
- 03
How dose translates by route
Oral ketamine delivers only about 25% active drug to the bloodstream, and sublingual or troche about 35%. Huberman uses himself as an example: at 100 kg, a 0.5 mg/kg clinical injection would be 50 mg. Matching it would take about 150 mg as a pill or about 200 mg as a troche. Doses of 1–2 mg/kg are in the anesthetic range.
- 04
What a 'K-hole' is
A K-hole is a pseudo-anesthetized state that happens when someone, usually recreationally, crosses from a sub-anesthetic into an anesthetic dose. Sensitivity varies a lot even at the same body weight, depending on metabolism. Very high doses carry risk of seizure and death, which is why clinical dosing is supervised.
- 05
R, S or racemic ketamine
After consulting clinicians, Huberman reports that trials so far suggest the combined R/S form is most potent for depression. S-ketamine, the most commonly prescribed form including as a nasal spray, comes second, and R-ketamine is least effective. He acknowledges individual reports may differ.
- 06
Learned helplessness models
Much early antidepressant research measured how long a rat or mouse kept swimming before 'giving up' in water, a quantifiable stand-in for learned helplessness. Researchers then tested which drugs lengthened or shortened that time. Huberman notes the limits: you can't ask an animal whether it's depressed, so behavior is the only readout.
OTHER RELEVANT
- 01
Know where your dose sits
Clinical antidepressant studies use about 0.5 mg/kg by IV or intramuscular injection. Because oral and sublingual routes are less bioavailable, take-home doses are higher in milligrams, and confusion about conversions is a real risk. Ketamine can raise liver enzymes, which is why some frequent users choose routes that bypass the liver.
- 02
Microdosing has no published support for depression
According to Huberman and his clinician colleagues, there is no published clinical evidence that microdosing ketamine treats depression. The positive data come from 0.5 mg/kg doses or their oral or sublingual equivalents.
- 03
Use it inside a clinical structure
Most evidence comes from supervised settings. Ketamine can be habit-forming, and repeated home use outside a clinic is a different situation from the trials, so work with a clinician on frequency and setting.
- 04
Pair treatment with anti-depressive behaviors
In the days after a dose, deliberately engage with rewarding work, people and healthy routines, since these are the inputs the more plastic circuits are built to respond to. Avoid bright light in the middle of the night, which activates the habenula.