Episode Description
In this episode of Neural Compass, host Mark Jacobstein sits down with Dr. John Krystal — co-founder of Freedom Biosciences, Yale psychiatrist, and one of the scientists most responsible for what we now know about ketamine and depression — for a conversation that starts with a collapsed hypothesis and ends with a genuinely new picture of what depression actually is.
In the 1990s, a series of depletion studies dismantled the dominant theory of depression. Serotonin and norepinephrine weren't the cause — they were coping mechanisms. Everything the field had funded pointed in the wrong direction. Krystal calls it an intellectual crisis. What he built from it changed psychiatry.
New episodes every two weeks. This one gets into the biology in a way that actually makes sense — and lands somewhere hopeful.
This episode covers:
- Why depleting serotonin in healthy people produces no depression — and what that means for every antidepressant on the market
- The three things ketamine does at the glutamate synapse within hours of a dose
- Why the antidepressant effect wears off — and what's being done to stop it
- The case for combining psychedelics with drugs that clip the hallucinations while leaving the efficacy intact
- How therapy administered 24 hours after ketamine — during peak neuroplasticity — outperforms either treatment alone
About the Speakers
John Krystal, Guest
joined the Yale faculty in 1988 and began the ketamine work a year later, when it was controversial enough to require years of justification before he could run a clinical trial. The trial results came back within 24 hours. He has spent the decades since understanding why.
He is co-founder and chief scientific officer of Freedom Biosciences, which is working to separate the antidepressant properties of psychedelics from their hallucinogenic ones. He thinks that's possible. The animal models suggest he's right.
Mark Jacobstein is the co-founder and president of Jimini Health. A longtime entrepreneur at the intersection of AI and health tech, he now leads Jimini’s mission to transform mental and behavioral health through clinically grounded, AI-powered care.
For healthcare executives, researchers, investors, and anyone who thinks the mental health crisis deserves serious answers — this is the show.