Visual Atlas · Cluster companion · 08
Psilocybin vs other psychedelics
Four compounds often discussed together, with genuinely different mechanisms underneath. Psilocybin and LSD are close cousins; MDMA and ketamine are different families that arrive at overlapping outcomes by other routes.
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In brief
Psilocybin and LSD are the close pair: both are 5-HT2A agonists, so they share a family resemblance, with LSD considerably longer-acting (roughly 8–12 hours versus psilocybin's 4–6). MDMA is an empathogen acting through serotonin release and oxytocin signalling — sociable and warming rather than classically psychedelic. Ketamine is a dissociative NMDA-receptor antagonist, mechanistically separate from all three.
They are grouped together because they overlap on outcomes — several can promote rapid neuroplasticity and have therapeutic signals — but the mechanisms differ. The Dölen 2023 work suggests a possible unifying thread. For microdosing specifically, psilocybin is the dominant compound; the others are mostly studied at full doses.
Visual walkthrough
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Same conversation, four different mechanisms
Psilocybin
A 5-HT2A agonist with an acute duration of roughly 4–6 hours. The dominant compound for microdosing and the reference point for this atlas.
LSD
Also a 5-HT2A agonist — hence the family resemblance to psilocybin — but considerably longer-acting, roughly 8–12 hours, which changes its practical use.
MDMA
An empathogen acting through serotonin release and oxytocin signalling. Warming and prosocial rather than classically psychedelic; studied notably for PTSD at full doses.
Ketamine
A dissociative NMDA-receptor antagonist — a different pathway entirely. It produces rapid plasticity and antidepressant effects, which is why it is discussed alongside psychedelics despite the different mechanism.
Shared outcomes, different routes
Several of these promote rapid neuroplasticity and show therapeutic signals, which is why they are grouped. The grouping is by outcome, not by a single shared receptor.
A possible unifying thread
The Dölen 2023 critical-period work proposes that these drugs share the ability to reopen a learning window, with duration tracking trip length — see that entry.
What the data shows — and how strong it is
Verdict
These substances differ in pharmacology, duration, evidence, risk, and law. Findings from one cannot be transferred automatically to another.
Common questions
Answered directly
Q · 01
What is the difference between psilocybin and LSD?
Both psilocybin and LSD are 5-HT2A receptor agonists, which is why they share a family resemblance in their effects. The main practical difference is duration: psilocybin's acute effects last roughly 4 to 6 hours, while LSD's last roughly 8 to 12 hours.
Q · 02
How is ketamine different from psilocybin?
Ketamine is a dissociative drug that works by blocking the NMDA glutamate receptor, whereas psilocybin works by activating the 5-HT2A serotonin receptor. Both can produce rapid neuroplasticity and antidepressant effects, but through entirely different pathways, so ketamine is grouped with psychedelics by outcome rather than by mechanism.
Q · 03
Why are these different drugs grouped together?
They are grouped because they overlap on outcomes — several promote rapid neuroplasticity and show therapeutic signals — even though their receptor mechanisms differ. The Dölen 2023 work proposes a possible unifying thread: a shared ability to reopen a learning critical period, with the duration tracking each drug's trip length.
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