Same receptor, different cells: the head-twitch survived, the synapse remodeling did not.
Weekly Science Digest, 17 Oct 2026 to 23 Oct 2026. 40 papers read, 12 preprints, 1 new trials.
1. One receptor, two jobs, two cell populations
Psilocybin's synapse remodeling and its head-twitch response run through different cells.
Deleting 5-HT2A from cortical layer 5 pyramidal neurons abolished psilocybin-induced synapse formation and pruning in mice but left the head-twitch response untouched; restoring it there was sufficient. A second paper finds 5-HT1B receptors on forebrain excitatory neurons are required for psilocybin's post-acute anxiolytic effect but not its acute behavioural effects.
How much weight it carries: Cell-type-specific mouse genetics with clean necessity and sufficiency tests; says nothing directly about human hallucination or clinical benefit. (Mice, Preclinical, Mechanism, Controlled, Peer reviewed)
Psilocybin shifted inflammation markers in Parkinson's, in a trial with no control arm.
The JAMA Psychiatry report pairs psilocybin therapy with changes in systemic inflammatory and mitochondrial stress markers in people with Parkinson disease and mood symptoms — nonrandomized, so the markers cannot be attributed to the drug. Separately, a four-arm ayahuasca trial in 28 healthy volunteers (seven per arm) found no dose effect on intelligence and a single isolated interaction, on delayed recall.
How much weight it carries: One uncontrolled biomarker trial and one 28-person four-arm RCT; neither is powered to establish an effect, and the Parkinson's study cannot attribute change to psilocybin. (Humans, No control group, Small sample, RCT, Double-blind, Placebo-controlled, n = 28, Peer reviewed)
News coverage of psilocybin is consistently more positive than the trial evidence behind it.
A systematic review in JAMA Network Open matched a decade of psilocybin clinical trials against contemporaneous media articles and compared tone, efficacy claims and safety content. Two accompanying pieces press the same point from inside the field: an implementation-science argument that current trials show proof of concept rather than readiness, and a commentary disputing how therapeutic alliance was analysed in COMPASS's treatment-resistant depression data.
How much weight it carries: A systematic comparison of published trials against media articles, plus two commentaries; descriptive, and cannot show that coverage changes patient behaviour. (Systematic review, Review, Peer reviewed)
4. What people actually do, and what it costs them
Three in four recreational MDMA users report a comedown, typically starting about a day later.
In a survey of 497 MDMA-experienced adults, 74.5% reported at least one episode of post-acute negative effects, with onset around 24 hours. A separate pair of studies on meditation plus drugs found alcohol (29%), cannabis (19%) and nicotine (16%) are combined with practice far more often than classic psychedelics (6%), with no consistent link to wellbeing in either direction.
How much weight it carries: Cross-sectional self-report from online panels; recall-dependent, self-selected, and cannot establish that the drugs caused the reported effects. (Humans, Survey, Observational, n = 497, Peer reviewed)
