Psilocybin Therapy: The Race for FDA Approval

Psilocybin is a naturally occurring psychedelic compound produced by more than 200 species of fungi, most belonging to the genus Psilocybe. When ingested, psilocybin is rapidly converted by the body into psilocin, which binds to serotonin 5-HT2A receptors in the brain. This triggers a cascade of neurological effects including altered perception, profound changes in mood and cognition, and what researchers describe as increased neural connectivity — brain regions that do not normally communicate begin to interact.

The most commonly known psilocybin mushroom is Psilocybe cubensis, a tropical and subtropical species found across the Americas, Southeast Asia, and Australia. In temperate climates, the liberty cap (Psilocybe semilanceata) is the most widespread species. The Pacific Northwest is home to several potent species including Psilocybe cyanescens and Psilocybe azurescens, the latter considered the most potent psilocybin mushroom known.

Psilocybin was first isolated in 1958 by Albert Hofmann, the Swiss chemist who had also discovered LSD. It was classified as a Schedule I controlled substance in the United States in 1970 under the Controlled Substances Act, effectively halting research for decades.

Modern psilocybin research restarted in the early 2000s, led by Roland Griffiths at Johns Hopkins University and Stephen Ross at NYU. Since then, a substantial body of clinical evidence has accumulated across multiple conditions.

The FDA designated psilocybin a “Breakthrough Therapy” for treatment-resistant depression in 2018, a status that accelerates the review process for drugs that show substantial improvement over existing treatments.

Compass Pathways is the furthest along in the regulatory process. The company is running five phase 3 trials across the United States, enrolling patients with treatment-resistant depression who have failed at least two adequate courses of antidepressant therapy. The trials are testing COMP360, a synthetic formulation of psilocybin, administered in a single 25mg dose under clinical supervision.

The phase 3 program was designed in consultation with the FDA and includes:

• Two pivotal efficacy trials comparing psilocybin 25mg to a 1mg active control (the 1mg dose is intended to produce minimal psychoactive effects while maintaining blinding)
• A long-term safety trial tracking outcomes over 12 months
• An open-label extension study for non-responders
• A study examining repeat dosing in patients who initially respond but later relapse

Compass expects to submit its New Drug Application (NDA) in 2026, with an FDA decision potentially in late 2026 or early 2027. If approved, psilocybin would become the first psychedelic compound to receive FDA marketing authorization.

The FDA's August 2024 rejection of MDMA-assisted therapy for PTSD (Lykos Therapeutics, formerly MAPS) cast a shadow over the psychedelic medicine field. The agency cited concerns about trial methodology, functional unblinding (patients could tell whether they received MDMA or placebo), and the difficulty of separating drug effects from therapy effects. Compass has stated that its trial design accounts for these concerns, but the MDMA rejection raised the bar for all psychedelic drug applications.

Psilocybin therapy is not “take a pill and go home.” It is a structured process involving preparation, a guided psychedelic experience, and integration. This model has been consistent across virtually all clinical trials and state-level programs.

While federal approval remains pending, several states have created their own legal frameworks for psilocybin access.

Psilocybin remains a Schedule I controlled substance under federal law in the United States, meaning it is classified as having “no currently accepted medical use” and a “high potential for abuse.” This classification creates a legal tension with state programs: Oregon's psilocybin service centers operate legally under state law while technically violating federal law, similar to the situation with state-legal cannabis.

The Department of Justice has not signaled an intent to enforce federal law against state-licensed psilocybin programs. However, the Schedule I status complicates research funding, banking for psilocybin businesses, and insurance coverage.

Internationally, psilocybin's legal status varies widely. It is legal for therapeutic use in Jamaica and the Netherlands (where psilocybin-containing truffles are sold openly). It is decriminalized in Portugal and parts of Brazil. Australia rescheduled psilocybin for therapeutic use in July 2023, making it available by prescription from specially authorized psychiatrists. Canada has granted individual exemptions for psilocybin therapy in palliative care settings.

Psilocybin is physiologically one of the safest psychoactive compounds known. It is not addictive, does not produce physical dependence, and has an extremely wide safety margin — the ratio between a psychoactive dose and a lethal dose is estimated at roughly 1,000:1. No deaths from psilocybin toxicity alone have been documented in clinical settings.

However, psilocybin is not without risks:

• Psychiatric contraindications: Psilocybin is contraindicated in people with a personal or family history of schizophrenia, psychotic disorders, or bipolar I disorder. The compound can trigger psychotic episodes in vulnerable individuals, and all clinical trials screen rigorously for these conditions.
• Psychological distress during sessions: Psilocybin can produce intense anxiety, fear, paranoia, or feelings of losing control during the experience. In clinical settings, trained facilitators manage these episodes through reassurance and grounding techniques. In uncontrolled settings, these experiences can be traumatic.
• Cardiovascular effects: Psilocybin causes modest, transient increases in heart rate and blood pressure. This is generally not dangerous in healthy individuals but may be a concern for people with uncontrolled hypertension or certain cardiac conditions.
• Drug interactions: Psilocybin interacts with serotonergic medications, particularly SSRIs and MAOIs. Most clinical trials require patients to taper off antidepressants before receiving psilocybin, which itself carries risks.
• Hallucinogen persisting perception disorder (HPPD): A rare condition in which visual disturbances (trailing images, halos, geometric patterns) persist long after the psychedelic experience has ended. Incidence in clinical trials has been extremely low but not zero.

The risk profile of psilocybin in controlled clinical settings is markedly different from unsupervised use. Almost all serious adverse events in the literature have occurred outside clinical contexts, often involving unknown doses, pre-existing psychiatric conditions, or concurrent substance use.

Clinical psilocybin therapy uses synthetically produced, precisely dosed psilocybin in capsule form. This is different from consuming wild psilocybin mushrooms, which carry additional risks including variable potency, species misidentification, and contamination.

The most serious risk of foraging for psilocybin mushrooms is misidentification. Several deadly species resemble psilocybin mushrooms, most notably Galerina marginata, a small brown mushroom that contains the same lethal amatoxins as the death cap and frequently grows in the same habitats as Psilocybe cyanescens. Multiple fatalities have been attributed to foragers confusing Galerina with Psilocybe species.

The legalization of psilocybin therapy does not make foraging for wild psilocybin mushrooms legal or safe. Even in Oregon and Colorado, possession of psilocybin mushrooms outside of licensed settings remains restricted.

If the FDA approves Compass Pathways' psilocybin therapy for treatment-resistant depression, it would represent a watershed moment for psychedelic medicine and for mental health treatment more broadly.

• Insurance coverage: FDA-approved treatments can be covered by insurance. This would make psilocybin therapy accessible to patients who cannot afford the $1,500–$3,500 out-of-pocket cost of state-level programs.
• Rescheduling: FDA approval would likely trigger DEA rescheduling of psilocybin from Schedule I (no accepted medical use) to Schedule II or III (accepted medical use with restrictions). This would ease research barriers and resolve some of the federal-state legal conflicts.
• Clinical access: Psychiatrists and other qualified prescribers could offer psilocybin therapy under FDA guidelines, dramatically expanding access beyond the handful of states with their own programs.
• Research acceleration: Rescheduling would simplify the regulatory burden on researchers, enabling larger, more diverse trials for additional indications including PTSD, addiction, and eating disorders.
• Precedent: Approval of psilocybin would establish a regulatory pathway for other psychedelic compounds, including MDMA (pending resubmission), LSD (in early-stage trials for anxiety), and DMT (being studied for depression).

FDA approval would not make psilocybin available over the counter or for unsupervised use. The drug would almost certainly be approved under a Risk Evaluation and Mitigation Strategy (REMS), requiring administration in certified clinical settings by trained healthcare providers. Patients would not take psilocybin home.