Magic Mushroom Glossary

A non-hallucinogenic analogue of LSD (2-bromo-lysergic acid diethylamide) with no significant 5-HT2A receptor activity. Studied as a preventive treatment for cluster headache, BOL-148 produces headache-frequency reductions without psychedelic effects — providing strong evidence that psilocybin's therapeutic action in headache disorders is neurological rather than psychological. (Karst et al., Cephalalgia, 2010)

A patient community term for using sub-psychedelic doses of psilocybin or LSD to abort or prevent cluster headache attacks. The practice was documented and shared online since the 1990s, formalised by the Clusterbusters patient advocacy organisation, and subsequently verified in a 2015 survey (Schindler et al., Journal of Psychoactive Drugs) showing 50–80% of cluster headache patients who tried psychedelics reported benefit — often at sub-hallucinogenic doses. This patient-led observation drove Yale's formal clinical investigation.

The ability to shift attention between tasks and adapt thinking patterns in response to new information. Impaired cognitive flexibility — sometimes called cognitive rigidity — is a core feature of both OCD and anorexia nervosa. Psilocybin is hypothesised to restore cognitive flexibility by increasing neuroplasticity via 5-HT2A receptor agonism in the prefrontal cortex, potentially disrupting rigid thought patterns that maintain compulsions and disordered eating behaviours.

Cortico-striato-thalamo-cortical circuit — a neural feedback loop connecting the orbitofrontal cortex, caudate nucleus, thalamus, and anterior cingulate cortex. Chronically hyperactive and "locked" in OCD, generating intrusive thoughts and compulsive responses. Psilocybin's proposed mechanism in OCD is normalisation of fronto-striatal connectivity within this loop — distinct from its default mode network disruption mechanism in depression.

Cytochrome P450 enzymes responsible for metabolising psilocin and many psychiatric medications in the liver. CYP2D6 is strongly inhibited by fluoxetine (Prozac) and paroxetine (Paxil), slowing their own clearance and potentially affecting psilocybin metabolism. CYP1A2 is strongly inhibited by fluvoxamine (Luvox), which may unpredictably increase psilocin blood levels — making that combination pharmacokinetically risky. Relevant when combining psilocybin with any psychiatric medication.

A brain network associated with self-referential thinking, rumination, and the sense of ego; psilocybin temporarily reduces its activity.

A temporary dissolution of the sense of self during a psychedelic experience, often described as profound and transformative.

A trained professional who supports and holds space during legal psilocybin therapy or retreat sessions.

A microdosing schedule: one day on, two days off, then repeat. Named after researcher James Fadiman.

Functional connectivity between the prefrontal cortex and the striatum. Abnormally elevated in OCD, contributing to the locked feedback loop of intrusive thoughts and compulsive behaviours. The Yale Phase 2 OCD trial (NCT05546658) uses fMRI to measure whether psilocybin normalises fronto-striatal connectivity at 48 hours post-dosing — providing the first neural biomarker evidence for psilocybin's mechanism in OCD.

A high dose of psilocybin mushrooms (typically 5g+) intended to produce an intense, often ego-dissolving experience.

The process of making meaning from a psychedelic experience and applying insights to daily life.

Soaking dried mushrooms in lemon juice before ingestion to speed onset and sometimes intensify effects.

Montgomery-Åsberg Depression Rating Scale — a validated 10-item clinician-rated scale measuring depression severity, scored from 0 (no symptoms) to 60 (severe). A 50% reduction from baseline is generally considered a treatment response; a score below 10 indicates remission. Used as a key secondary outcome measure in psilocybin depression trials including the landmark 2021 NEJM vs escitalopram study. Distinct from the QIDS-SR, which is self-reported.

Taking sub-perceptual doses of psilocybin on a regular schedule for subtle cognitive and emotional benefits.

The vegetative part of a fungus, consisting of a network of fine white filaments that eventually produces mushrooms.

The brain's ability to form new neural connections and change over time; psilocybin may temporarily increase it.

A clinical trial design that tests whether a new treatment is no worse than an active comparator by more than a pre-defined margin — rather than testing whether it is better (superiority). The 2021 NEJM psilocybin vs escitalopram trial was a non-inferiority study: psilocybin was found non-inferior to the SSRI on the primary QIDS-SR outcome, meaning it performed at least as well. This is a meaningful finding — not a consolation. Non-inferiority with fewer side effects and a shorter treatment course represents a clinically significant advantage.

The pharmacologically active compound that psilocybin converts to in the body, responsible for psychedelic effects.

A naturally occurring psychedelic compound found in certain mushrooms that produces altered states of consciousness.

A dosing schedule used in cluster headache and migraine trials — typically three doses of psilocybin (~10 mg each), administered approximately five days apart, over a two-week period. Distinct from the single high-dose sessions used in depression and PTSD protocols. The therapeutic effect in headache disorders does not correlate with the intensity of the psychedelic experience, suggesting a direct neurological mechanism rather than a psychotherapy-mediated one. (Schindler et al., Journal of Neurological Sciences, 2024)

The combination of mindset (set) and environment (setting) that shapes a psychedelic experience.

Reproductive cells produced by mushrooms, used to start new cultures and legal to possess in most US states.

A cluster of symptoms occurring when SSRIs are stopped abruptly or tapered too quickly. Symptoms include dizziness, nausea, flu-like sensations, irritability, insomnia, and "brain zaps" — brief electric shock-like sensations in the head or extremities. Severity varies by drug: highest risk with paroxetine and venlafaxine; lowest with fluoxetine (despite its long washout time). Always requires a clinician-supervised taper. Relevant for anyone considering transitioning from SSRIs to psilocybin therapy.

Paul Stamets' microdosing protocol: psilocybin plus Lion's Mane and niacin, usually 4 days on and 3 days off.

The trigeminal nerve system (cranial nerve V) responsible for transmitting pain signals from the face, scalp, and meninges to the brain. Becomes sensitised and hyperactivated during cluster headache and migraine attacks. Psilocybin may modulate trigeminal pain pathways via 5-HT2B and 5-HT2C receptor activity — a mechanism distinct from its 5-HT2A-mediated antidepressant effects. This distinction may explain why psilocybin's headache benefits do not correlate with psychedelic intensity.

A sober person who remains present during a psychedelic experience to provide support and ensure safety.

Yale-Brown Obsessive Compulsive Scale — the primary validated outcome measure used in OCD clinical research. Assesses symptom severity across obsessions and compulsions on a 0–40 scale (0 = no symptoms, 40 = extreme). A reduction of 35% or more from baseline is generally considered clinically significant. Used in all psilocybin OCD trials as the key efficacy endpoint. In the 2006 University of Arizona pilot study, participants showed 23–100% Y-BOCS reductions across dosing sessions. (Moreno et al., Journal of Clinical Psychiatry, 2006)