A Two-Threshold Model of Psilocybin Response Explains Variability in Psychedelic-Assisted Therapy for Treatment-Resistant Depression
Bottom line: A two-threshold model suggests that psilocybin’s effectiveness in treatment-resistant depression may depend on both a universal dose threshold and individual psychological factors that influence transformative experiences.
A single 25 mg dose of psilocybin helps about a third of people with treatment-resistant depression — but not the rest. Same drug, same dose, same protocol. No one knows why. Until now.
The Two-Threshold Model: Why Some Respond, Some Don’t
In the world of psychedelic science, one size doesn’t fit all — and this study shows why. The COMP006 Phase 3 trial found that a single 25 mg dose of psilocybin worked for 39% of people with treatment-resistant depression, but not for the other 61%. The same dose, the same protocol, the same drug. The question is: why?
The answer lies in a model that splits the experience into two distinct phases — not just a simple dose-response curve. The first threshold, Dc1, is a universal point at 18 ±1 mg, where the drug transitions from a normal state of consciousness to an altered one. This is the moment when the brain starts to change, and it’s consistent across more than 700 subjects in two separate datasets.
The second threshold, Dc2, is where the real magic happens — but it’s not about the dose at all. It’s about the person.
Dc2, the threshold for transformative mystical experience, is individualized. It’s not a fixed number, but something that depends on psychological factors like set, setting, and preparation. This means that even if two people take the same dose, one might feel a profound shift while the other doesn’t — and that shift is what predicts therapeutic benefit. The model is supported by over 3,000 subjects across twelve lines of evidence, including pharmacokinetic data showing that the variation in subjective response is 52 times greater than the variation in plasma drug levels.
The Science of Consciousness: From Dose to Destiny
The first threshold, Dc1, is the point where psilocybin crosses the line from being a regular drug to something more — a catalyst for change. It’s not about the dose itself, but the brain’s response to it. Five independent analytical methods confirmed this transition, all converging within 1.5 mg — a small range that suggests a biological mechanism at play.
The second threshold, Dc2, is where the real transformation begins. This isn’t a matter of how much drug is in the blood, but how the mind and body interact with it. The study found that mystical experience intensity — not dose — predicts antidepressant outcomes. This is a huge shift in how we think about psychedelic therapy. It suggests that the psychological context, not the chemical dose, is the key to unlocking healing.
The implications are profound. If Dc2 is determined by psychological factors, then the way we prepare for a session, the environment we’re in, and our mindset all play a critical role. This isn’t just about taking a pill — it’s about creating the right conditions for transformation.
A New Framework for Understanding Psychedelic Therapy
This two-threshold model offers a new way to think about psychedelic-assisted therapy. It explains why the same dose can have such different effects, and it shifts the focus from pharmacology to psychology. The model is not just theoretical — it’s supported by historical data from six randomized controlled trials of LSD for alcoholism, which showed near-zero inter-study heterogeneity (I2 ≈ 0%). This suggests that the model is not just a hypothesis, but a reliable framework for understanding how psilocybin works.
The study also highlights the importance of psychological preparation. According to the model, intensive psychological preparation should increase therapeutic response more effectively than dose escalation above Dc1. This means that the way we approach psychedelic therapy — the preparation, the setting, the mindset — is just as important as the dose itself.
This is a paradigm shift in psychedelic research. It moves the conversation from what the drug does to what the person brings to the experience. It’s a reminder that healing is not just a chemical reaction — it’s a deeply personal and psychological process.
Frequently Asked Questions
Q: Does this model apply to other psychedelics?
A: The study focuses on psilocybin, but the two-threshold model could potentially apply to other psychedelics like LSD or ayahuasca. However, more research is needed to confirm this across different substances.
Q: Can the second threshold be predicted?
A: The second threshold is individualized and depends on psychological factors like set, setting, and preparation. While these factors can be measured and assessed, they don’t provide a precise prediction of when Dc2 will be reached.
Q: Is the model applicable to all types of psychedelic therapy?
A: The model is based on data from treatment-resistant depression, but it may have broader applications. However, the study does not claim universal applicability to all conditions or populations.
Q: What are the implications for clinical practice?
A: The model suggests that psychological preparation is a critical component of psychedelic therapy. This could lead to more personalized approaches, where the focus is not just on the dose but on the preparation and context of the experience.
Q: How does this model differ from previous theories?
A: Previous theories often focused on the pharmacological effects of psychedelics, assuming that higher doses would lead to better outcomes. This model shifts the focus to the psychological and contextual factors that influence the therapeutic response.
Sources
- ¶Preprint (Research Square) — A Two-Threshold Model of Psilocybin Response Explains Variability in Psychedelic-Assisted Therapy for Treatment-Resistant Depression (2026-09-09)
Educational Disclaimer
This article is for informational and educational purposes only. It is not medical advice, mental health advice, diagnosis, treatment guidance, or a recommendation to use any substance, supplement, therapy, or protocol.
We review publicly available research and explain what the evidence may suggest. Some studies may be early-stage, observational, animal-based, lab-based, theoretical, or incomplete. Always consult a qualified professional before making health-related decisions.
If you or someone you know is struggling, you are not alone. In the US, call or text 988 (Suicide & Crisis Lifeline). Elsewhere, contact your local emergency or crisis service.
Researched and drafted by Spore, ShroomWire’s AI research assistant, and reviewed by the ShroomWire editorial team before publishing.
