Novel psychopharmacological therapies for psychiatric disorders: psilocybin and MDMA

Grob and colleagues frame their Personal View against a longstanding clinical problem: conventional psychopharmacology and psychotherapy, while beneficial for many patients, often fail to cure underlying psychiatric disorders and can be limited by modest efficacy, non-response, and adverse effects from long-term dosing. The authors note growing interest in improving psychological treatments, especially for conditions such as post-traumatic stress disorder (PTSD), existential distress at the end of life, and treatment-resistant disorders, and they highlight patient preference for psychotherapy over medication as a further impetus for novel approaches. This paper outlines and evaluates a model in which classic psychedelics (psilocybin) and the entactogen MDMA are administered on one or a few occasions to catalyse or augment psychotherapy. Rather than presenting these compounds as daily pharmacotherapies, Grob and colleagues describe them as adjuncts that can facilitate intense therapeutic experiences thought to produce rapid and potentially durable clinical benefits. The authors state their aim as reviewing evidence from early and recent clinical studies of psilocybin- and MDMA-assisted psychotherapy, discussing mechanisms, safety considerations, challenges (for example masking), and directions for future research.

This article is a narrative Personal View rather than a systematic review or meta-analysis. The authors drew on literature known to them from prior investigational new drug work and symposium preparation, supplemented by targeted searches using PubMed and Google Scholar when specific questions arose. They state that these additional searches were not planned prospectively and that reference selection was therefore not systematic. When describing specific clinical trials and pilot studies, the paper relies on published reports, earlier research from the 1950s–1970s, and information provided to the authors via personal communication from investigators running more recent trials. The authors also reference safety guidelines developed by the Johns Hopkins psilocybin research group and report on phase 1 and phase 2 clinical trials of MDMA and psilocybin; details of individual trial designs (for example double-blind, placebo-controlled designs) are summarised in the text where available. Where fMRI or other mechanistic substudies are mentioned, the paper notes that some results are pending or that protocols are planned.

Psilocybin-assisted psychotherapy: Early mid-20th-century investigations suggested therapeutic potential for classic hallucinogens in treatment-refractory conditions, but research largely halted for political reasons. More recently, small clinical studies have reopened investigation. A double-blind, placebo-controlled crossover study at Harbor-UCLA (12 patients serving as their own controls) administered a moderate dose of psilocybin (0.2 mg/kg) and reported safe physiological and psychological responses, no clinically significant adverse events during sessions, and significant reductions in anxiety measured by the State-Trait Anxiety Inventory at 1 and 3 months after treatment. Mood improvement measured by the Beck Depression Inventory reached significance at 6 months. The authors note that higher-dose trials at Johns Hopkins and New York University have regulatory approval and that publication of those results was expected (personal communication). Additional findings summarised include a Swiss LSD study that showed a strong effect size for reduction in state and trait anxiety, and a pilot study by Bogenschutz and colleagues in which a single dose of psilocybin reduced drinking behaviour and craving in ten individuals with alcohol use disorder. Mechanistically, psilocybin's neuropharmacology is linked primarily to agonism of serotonergic 5-HT2A receptors, with downstream second-messenger and gene-expression effects likely contributing. Safety guidance and careful screening are emphasised as essential to minimise risks. MDMA-assisted psychotherapy: MDMA was used clinically in the late 1970s and early 1980s and has been studied more formally in recent decades. The authors report that more than 1100 individuals have received MDMA in Phase I or Phase II trials without unexpected drug-related serious adverse events; the sole reported drug-related serious adverse event was transient ventricular ectopy requiring overnight observation. Two completed double-blind, placebo-controlled Phase II trials for treatment-resistant PTSD are described. In the first completed Phase II trial of 20 chronic, treatment-resistant PTSD patients, those randomised to MDMA with psychotherapy experienced significantly greater reductions in PTSD symptoms than those given inactive placebo with psychotherapy; 83% of the MDMA group no longer met criteria for PTSD versus 25% of placebo participants. When the placebo group later received open-label MDMA-assisted psychotherapy, they achieved similar improvement. A long-term follow-up (mean 45.4 months after treatment) found that at least 74% had durable remission of PTSD symptoms. A Swiss study with 12 patients did not reach statistical significance on Clinician-Administered PTSD Scale reductions but reported an effect size greater than 1 and significant reductions on the Posttraumatic Diagnostic Scale. Mechanistic and ancillary findings: The paper summarises putative mechanisms for MDMA's facilitative effects on psychotherapy, including monoamine release (serotonin primarily, with dopamine and norepinephrine), oxytocin and prolactin release, and functional brain changes such as decreased amygdala and hippocampal activity and altered resting-state functional connectivity. Small neuroimaging substudies are underway or planned; for example, a substudy of MP-8 examining fMRI before and after MDMA-assisted psychotherapy is noted as having results pending. The authors also highlight practical challenges such as difficulty maintaining masking (blinding) because of the prominent subjective effects of these drugs, and they report that some psilocybin studies have used active placebos or open-label designs.

Grob and colleagues interpret the accumulated evidence as suggestive that psilocybin and MDMA, when used in carefully controlled settings alongside structured psychotherapy, have therapeutic promise for populations that are often refractory to existing treatments, including patients with end-of-life anxiety, alcohol use disorder, and chronic PTSD. They emphasise that the treatment model differs from standard daily pharmacotherapy: these compounds are administered on one or a few occasions to catalyse a therapeutic process, with substantial preparatory and integration psychotherapy before and after drug sessions. The authors point out differences in session structure between the two approaches: MDMA sessions typically alternate talking with periods of inner focus, whereas psilocybin sessions concentrate inner focus during the drug effect with more talking before and after. The paper acknowledges important limitations and uncertainties. Sample sizes in many clinical studies have been small, some trials were open-label or used imperfect active placebos, and research was historically impeded by regulatory and political barriers. Debates persist about the neurotoxic risks observed in some retrospective studies of recreational MDMA users; the authors note methodological confounders in that literature and stress the need for rigorous prospective safety data. Masking remains a methodological challenge because the drugs' subjective effects are conspicuous, although blinded independent raters are feasible and could be further protected in larger trials. In terms of implications, the authors call for expeditious, rigorous clinical trials to establish efficacy and safety, identification of suitable patient populations, elucidation of neuropsychopharmacological mechanisms, and development of standardised safety and treatment manuals. They also encourage qualitative analyses of the extensive video archives from recent studies to study phenomenology and recommend that research and funding decisions be driven by scientific evidence and patient needs rather than political or financial pressures. The authors underscore the importance of maintaining strict screening and monitoring procedures to reduce risk in clinical research settings.