Understanding variations in knowledge and attitudes of psychiatrists to psilocybin therapy is important for the collective discourse about the potential impact on clinical practice and public health in Ireland.

A 28-item questionnaire was designed based on previous studies and distributed to psychiatrists in Ireland via online mailing lists and at in-person academic events.

151 psychiatrists completed the questionnaire (73.3% were under 40 years of age, 76.0% were trainees, and 49.0% were female). In the total sample, 81.5% agreed that psilocybin therapy shows promise in the treatment of psychiatric disorders and 86.8% supported funding research, 86.8% would be willing to refer a patient if it was licensed and indicated, and 78.1% would consider the treatment for themselves, if indicated. Conversely, 6.6% agreed that psilocybin therapy was unsafe even under medical supervision, and 21.9% thought it was potentially addictive. 15.9% of the total sample reported at least one concern including, lack of robust evidence, long-term effectiveness, superiority to current interventions, potential harmful effects, cost and accessibility, and impartiality. Less than half of respondents felt knowledgeable (40.0%) and 9.9% felt adequately prepared to participate in psilocybin therapy. Consultant psychiatrists trended towards less optimism for a potential role in bipolar depression and emotionally unstable personality disorder compared to trainee psychiatrists.

Overall psychiatrists in Ireland held positive attitudes towards psilocybin therapy. However, there was a lack of knowledge evident. Addressing the knowledge gap and aligning with the best available evidence will be key if psychedelic therapy is to prevail in a clinical setting.

To investigate the association between pre-trial expectancy, suggestibility, and response to treatment in a trial of escitalopram and investigational drug, COMP360, psilocybin, in the treatment of major depressive disorder (ClinicalTrials.gov registration: NCT03429075).

We used data (n = 55) from our recent double-blind, parallel-group, randomized head-to-head comparison trial of escitalopram and investigational drug, COMP360, psilocybin. Mixed linear models were used to investigate the association between pre-treatment efficacy-related expectations, as well as baseline trait suggestibility and absorption, and therapeutic response to both escitalopram and COMP360 psilocybin.

Patients had significantly higher expectancy for psilocybin relative to escitalopram; however, expectancy for escitalopram was associated with improved therapeutic outcomes to escitalopram, expectancy for psilocybin was not predictive of response to psilocybin. Separately, we found that pre-treatment trait suggestibility was associated with therapeutic response in the psilocybin arm, but not in the escitalopram arm.

Overall, our results suggest that psychedelic therapy may be less vulnerable to expectancy biases than previously suspected. The relationship between baseline trait suggestibility and response to psilocybin therapy implies that highly suggestible individuals may be primed for response to this treatment.

Previous research has proposed that there may be potential synergies between psychedelic and meditation interventions, but there are still knowledge gaps that merit further investigation.

Using a longitudinal observational research design with samples representative of the US and UK adult population with regard to sex, age, and ethnicity (N = 9732), we investigated potential associations between self-reported psychedelic use and meditation practice.

The follow-up survey was completed by 7667 respondents (79% retention rate), with 100 respondents reporting psychedelic use during the 2-month study period (1.3% of follow-up respondents). In covariate-adjusted regression models, psychedelic use during the study period was associated with greater increases in the number of days of mindfulness meditation practice in the past week (B = 0.40, p = 0.004). Among those who reported psychedelic use during the study period, covariate-adjusted regression models revealed that the subjective experience of insight during respondents' most intense psychedelic experience in that period was also associated with greater increases in the number of days of mindfulness and loving-kindness or compassion meditation practice in the past week (B = 0.42, p = 0.021; B = 0.38, p = 0.017). Notably, more days of loving-kindness or compassion meditation practice in the past week at baseline was associated with less severe subjective feelings of death or dying during respondents' most intense psychedelic experience in the study period (B = −0.29, p = 0.037).

Psychedelic use might lead to greater engagement with meditation practices such as mindfulness meditation, while meditation practices such as loving-kindness or compassion medication might buffer against certain challenging experiences associated with psychedelic use.

Randomised controlled trials (RCTs) of psilocybin have reported large antidepressant effects in adults with major depressive disorder and treatment-resistant depression (TRD). Given psilocybin's psychedelic effects, all published studies have included psychological support. These effects depend on serotonin 2A (5-HT2A) receptor activation, which can be blocked by 5-HT2A receptor antagonists like ketanserin or risperidone. In an animal model of depression, ketanserin followed by psilocybin had similar symptomatic effects as psilocybin alone.

To conduct a proof-of-concept RCT to (a) establish feasibility and tolerability of combining psilocybin and risperidone in adults with TRD, (b) show that this combination blocks the psychedelic effects of psilocybin and (c) provide pilot data on the antidepressant effect of this combination (compared with psilocybin alone).

In a 4-week, three-arm, ‘double dummy’ trial, 60 adults with TRD will be randomised to psilocybin 25 mg plus risperidone 1 mg, psilocybin 25 mg plus placebo, or placebo plus risperidone 1 mg. All participants will receive 12 h of manualised psychotherapy. Measures of feasibility will include recruitment and retention rates; tolerability and safety will be assessed by rates of drop-out attributed to adverse events and rates of serious adverse events. The 5-Dimensional Altered States of Consciousness Rating Scale will be a secondary outcome measure.

This trial will advance the understanding of psilocybin's mechanism of antidepressant action.

This line of research could increase acceptability and access to psilocybin as a novel treatment for TRD without the need for a psychedelic experience and continuous monitoring.

There is growing evidence to support the use of the psychedelic drug psilocybin for difficult-to-treat depression. This paper compares the cost-effectiveness of psilocybin-assisted psychotherapy (PAP) with conventional medication, cognitive behavioural therapy (CBT), and the combination of conventional medication and CBT.

A decision model simulated patient events (response, remission, and relapse) following treatment. Data on probabilities, costs and quality-adjusted life years (QALYs) were derived from previous studies or from best estimates. Expected healthcare and societal costs and QALYs over a 6-month time period were calculated. Sensitivity analyses were used to address uncertainty in parameter estimates.

The expected healthcare cost of PAP varied from £6132 to £7652 depending on the price of psilocybin. This compares to £3528 for conventional medication alone, £4250 for CBT alone, and £4197 for their combination. QALYs were highest for psilocybin (0.310), followed by CBT alone (0.283), conventional medication alone (0.278), and their combination (0.287). Psilocybin was shown to be cost-effective compared to the other therapies when the cost of therapist support was reduced by 50% and the psilocybin price was reduced from its initial value to £400 to £800 per person. From a societal perspective, psilocybin had improved cost-effectiveness compared to a healthcare perspective.

Psilocybin has the potential to be a cost-effective therapy for severe depression. This depends on the level of psychological support that is given to patients receiving psilocybin and the price of the drug itself. Further data on long-term outcomes are required to improve the evidence base.

The 5-HT2A agonist classic psychedelic, psilocybin (O-phosphoryl-4-hydroxy-N,N-dimethyltryptamine) is a tryptophan, indole-based alkaloid present in up to 2% of certain hallucinogenic “magic” mushroom species; typically Psilocybe azurescens, semilanceata, and cyanescens,. In addition, mushrooms may contain psilocin (4-hydroxy-N,N-dimethyltryptamine). Both are indolylalkylamines (tryptamines); other naturally occurring tryptamine compounds include norbaeocystin, baeocystin, norpsilocin, and aeruginascin. A putative synergistic contribution of these compounds has been referred to as the “entourage” effect. Aeruginascin (N,N,N-trimethyl-4-phosphoryloxytryptamine) is found naturally in Inocybe aeruginascens and Pholiotina cyanopus mushroom species and ingestion reportedly invokes elevation in mood without accompanying hallucinogenic effects:

To review the pharmacology of aeruginascin and putative entourage effect.

The extant literature on aeruginascin was reviewed and discussed.

Methylation of aeruginascin results in an active metabolite, 4-hydroxy-N,N,N-trimethyltryptamine (4-HO-TMT) which has been shown to bind at 5-HT1A, 5-HT2A, and 5-HT2B receptors with Inhibition Constants (Ki) of 4400, 670, and 120 nM respectively; compared with psilocybin’s binding of 567.4, 107.2 and 4.6 nM respectively. Further, 4-HO-TMT does not bind at the 5-HT3 receptor, and as a quaternary trimethylammonium compound it is less likely to be able to cross the blood-brain-barrier (BBB).

There are very limited data with respect to the pharmacology of aeruginascin. Its activity at serotonin receptors is less by several orders of magnitude than psilocybin and it has potentially less brain penetrance. Given that it is found in different mushrooms species the data would suggest that its direct contribution to any entourage effect is limited. Further research in needed into other naturally occurring tryptamine compounds.

PC is a member of the Scientific Advisory Board of Zylorion. AA, EB, JC, CE have no disclosures to report.

Psilocybin is a psychedelic drug found in mushrooms, often referred to as magic mushrooms due to its visual and auditory hallucinations effects upon ingestion. It is a Schedule I drug per DEA, and the FDA has not approved psilocybin for medicinal purposes. However, recent studies have shown promising therapeutic use to treat depression.

To identify current use, prevalence, and its association with depression in adolescents.

The National Survey on Drug Use and Health survey data from 2008-18 studied adolescent data (12-17 years), who responded, “ever used psilocybin (mushrooms)” and “lifetime major depressive episode (MDE).” The association between the psilocybin use and MDE status was analyzed in SAS 9.4 through multivariate logistic regression for odds ratio (OR) and 95% confidence interval (CI).

A total of 172745 adolescents were included in this study, of which 2469 ever used psilocybin in their lifetime, and 170276 responded no lifetime use. The psilocybin ever lifetime users were 17 years old (42%vs.17%,p<0.001), male (60%vs.51%,p<0.001), and non-Hispanic White (71%vs.55%,p<0.001) in comparison to non-users. Among psilocybin user group, 31% of respondents had lifetime MDE, compared to 16% of the lifetime psilocybin non-user group participants (p<0.001). The odds of association of psilocybin use among participants with MDE were 2.17 times compared to those without MDE (CI: 1.93-2.44,p<0.001).

We identified a significant association between psilocybin use and MDE among adolescents, which raises public health concerns about its illegal use, abuse, and toxicity potential. Future clinical studies should assess its clinical safety, efficacy, and addictive properties.

No significant relationships.

Psilocybin is a naturally occurring plant alkaloid in mushrooms and a prodrug of psilocin. It is a serotonin receptor (5-HT2A) agonist and known psychedelic, with similar hallucinatory properties to lysergic acid diethylamide (LSD). It has been identified as a safe and effective option in treatment-resistant depression. Literature focus mainly on its use on depressive but its interest in other psychiatric disorders such as obsessive-compulsive disorder (OCD) has grown.

To review the clinical evidence for the use of hallucinogens such as psilocybin in OCD.

Non-systematic review of literature found on PubMed/MEDLINE, Web of Science and Google Scholar, using the keywords “obsessive-compulsive disorder”, “psilocybin” and “hallucinogens”. Articles may include clinical trials, case report or case series. Articles found were admitted according to their relevance for the topic in review; only articles in English were included. Ongoing research trials on this topic were checked on ClinicalTrials.gov.

So far, only one open-label non-randomized study directly assessed the effects of psilocybin on OCD patients that found acute reductions of obsessive-compulsive symptoms. Case reports of patients improving with off-label use of psilocybin are reported. There are two ongoing phase I research trials, aiming to explore the effect of the substance on symptomatology, hypothesizing that psilocybin will normalize cerebral connectivity and thus correlate with clinical improvement.

More research to establish the usefulness of psilocybin in OCD patients is needed; the collected data is encouraging are there may be a role for its use on this disorder.

Recently there has been renewal in interest of psychedelic research. Classic psychedelics such as lysergic acid diethylamide (LSD), psilocybin and mescaline act pharmacologically as agonists at the 5-HT2A receptor. The entactogens like methylenedioxymethamphetamine (MDMA), acts as a serotonin, dopamine and noradrenaline agonist. All of these drugs are potential candidates in the treatment of multiple psychiatric illnesses.

The authors intend to review the literature on the clinical application of psychedelic drugs in psychiatric disorders.

Non-systematic review of the literature.

In recent clinical trial the psychedelic is given with psychotherapeutic input. In a supportive setting, psychedelics produced immediate and significant anti-depressant and anxiolytic effects that were endured for several months. Randomized clinical trials support the efficace of psilocybin in the treatment of depression and those with anxiety and depression symptoms provoked by life-threatening cancer. There have also been studies showing efficacy in both alcohol and tobacco dependence. When administered safely LSD can reduce anxiety and have anti-addictive property. Randomized clinical trials support the efficacy of MDMA in the treatment of PTSD. Psychedelics were well-tolerated, few adverse effects have been reported. The most common adverse effects were transient anxiety, short-lived headaches, nausea and mild increases in heart rate and blood pressure, with no persisting adverse effects. Serious adverse events, such as persistent psychosis and suicidality, have not been demonstrated.

Psychedelics appear to be effective in multiple psychiatric disorders and are well-tolerated, although further evidence is required, to better see they therapeutic potential.

No significant relationships.

Major depressive disorder is a highly prevalent clinical condition, affecting more than 300 million individuals worldwide. About 1/3 of patients with MDD fail to achieve remission despite treatment with multiple antidepressants and are considered to have treatment-resistant depression (TRD). Novel antidepressants with rapid and sustained effects on mood and cognition could represent a breakthrough in the TRD and may potentially improve or save lives. Psilocybin, a classic hallucinogen, more commonly found in the Psilocybe mushrooms has a combined serotonergic and glutamatergic action. The preliminary evidence of antidepressant effects of psilocybin-assisted therapy indicates the potential of psilocybin-assisted therapy as a novel antidepressant intervention.

The authors elaborate a narrative literature review about the effects of Psilocybin-based therapy on patients diagnosed with treatment-resistant depression.

PubMed database searched using the terms “Treatment-Resistant Depression AND Psilocybin” and targeting clinical trials. References of selected articles and review articles were also assessed.

2 articles evaluate psilocybin effects in 32 patients with TRD and showed that two doses of psilocybin alongside psychological support significantly reduces depressive symptoms. All patients presented some reduction in symptoms from baseline to one week after the second dose and reproduced immediate and substantial improvements in depression that ultimately could sustain up to 6 months.

Psilocybin-assisted therapy is a very appealing new possibility in the treatment of depression. However, due to the small populations of the existing trials, future studies are needed to prove this positive association and to fully understand Psilocybin’s mechanisms of actions and effects.

No significant relationships.

Scientific interest in the therapeutic effects of classical psychedelics has increased in the past two decades. The psychological effects of these substances outside the period of acute intoxication have not been fully characterized. This study aimed to: (1) quantify the effects of psilocybin, ayahuasca, and lysergic acid diethylamide (LSD) on psychological outcomes in the post-acute period; (2) test moderators of these effects; and (3) evaluate adverse effects and risk of bias.

We conducted a systematic review and meta-analysis of experimental studies (single-group pre-post or randomized controlled trials) that involved administration of psilocybin, ayahuasca, or LSD to clinical or non-clinical samples and assessed psychological outcomes ⩾24 h post-administration. Effects were summarized by study design, timepoint, and outcome domain.

A total of 34 studies (24 unique samples, n = 549, mean longest follow-up = 55.34 weeks) were included. Classical psychedelics showed significant within-group pre-post and between-group placebo-controlled effects on a range of outcomes including targeted symptoms within psychiatric samples, negative and positive affect-related measures, social outcomes, and existential/spiritual outcomes, with large between-group effect in these domains (Hedges' gs = 0.84 to 1.08). Moderator tests suggest some effects may be larger in clinical samples. Evidence of effects on big five personality traits and mindfulness was weak. There was no evidence of post-acute adverse effects.

High risk of bias in several domains, heterogeneity across studies, and indications of publication bias for some models highlight the need for careful, large-scale, placebo-controlled randomized trials.

Psilocybin is a serotonin receptor agonist with a therapeutic potential for treatment-resistant depression and other psychiatric illnesses. We investigated whether the administration of psilocybin had an antidepressant-like effect in a rat model of depression.

Using the Flinders Sensitive Line (FSL) rat model of depression, we assessed the antidepressant-like effect of psilocin and psilocybin, measured as a reduction in immobility time in the forced swim test (FST). We measured locomotor activity in an open field test (OFT) to control for stimulant properties of the drugs. We performed a set of experiments to test different doses, treatment paradigms, and timing of the tests in relation to the drug administration.

Psilocin and psilocybin showed no effect on immobility, struggling, or swimming behaviour in the FST and no effect on locomotor activity in the OFT. FSL rats did show significantly more immobility than their control strain, the Flinders Resistant Line, as expected.

Psilocin and psilocybin showed no antidepressant-like effect in the FSL rats, despite a positive effect in humans. This suggests that other animal models of depression and other behavioural tests may be more appropriate for translational studies in the effects of psilocybin.