Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology
January 1, 2023
Abigail E. Calder, Gregor Hasler
303 citations
Classic psychedelics like LSD, psilocybin, and ayahuasca may help treat depression, anxiety, and addiction, with clinical improvements lasting months or years. The leading theory is that these drugs rapidly and persistently stimulate neuroplasticity. This review examines evidence that psychedelics promote neuroplasticity, including dendritogenesis, synaptogenesis, neurogenesis, and plasticity-related gene expression, particularly in the prefrontal cortex and hippocampus. It also considers the doses required—hallucinogenic versus microdoses—and how long neuroplastic changes last. The authors discuss consequences for patients and healthy individuals and identify key research questions for future study.
European Neuropsychopharmacology
June 21, 2023
Seline Mock, Nicole Friedli, Patrick Pasi et al.
46 citations
Eating disorders are serious illnesses with high mortality and comorbidity. Psychedelic-assisted therapy shows promise for common comorbidities like mood disorders, PTSD, and substance use disorders, and may also benefit eating disorders themselves. This review summarizes preliminary data on ketamine, MDMA, psilocybin, and ayahuasca for anorexia nervosa, bulimia nervosa, and binge eating disorder. Preliminary evidence suggests psychedelic-assisted therapy may be effective for anorexia and bulimia, with very little data on binge eating disorder. Potential mechanisms include improving body image beliefs, normalizing reward processing, promoting cognitive flexibility, and facilitating trauma processing, alongside general therapeutic factors. Safety concerns and future research recommendations are discussed.
Journal of Psychopharmacology
January 12, 2024
Antonin Rouaud, Gregor Hasler, Abigail E. Calder
36 citations
Microdosing psychedelics like LSD and psilocybin has become popular, but its long-term effects on heart health are unknown. These drugs share structural similarities with medications that raise the risk of cardiac fibrosis and valvulopathy when taken regularly. This review evaluates the evidence that microdosing for months or more could increase the risk of cardiac fibrosis, discusses the role of the 5-HT2B receptor in drug-induced cardiac fibrosis, and recommends safety evaluations for future studies.
J Psychopharmacol
February 28, 2023
Polina Ponomarenko, Federico Seragnoli, Abigail E. Calder et al.
22 citations
Combining psychedelic substances with group psychotherapy may enhance group connectedness and interpersonal learning, potentially improving prosocial behavior by providing direct opportunities to practice new behavioral patterns. Challenges include a more rigid therapy structure and possible loss of patient openness, which can be mitigated by adequate therapeutic training. The article analyzes existing clinical and neurobiological literature using Yalom's 11 therapeutic factors as a framework, aiming to support clinical research on this approach.
Journal of Affective Disorders
November 15, 2024
Abigail E. Calder, Gregor Hasler
20 citations
A new standardized tool, the Swiss Psychedelic Side Effects Inventory (SPSI), was developed to systematically record clinically relevant side effects of psychedelics and MDMA, including their severity, duration, impact, and treatment-relatedness. The SPSI was constructed from previous research and pilot tested in 145 participants across three studies, with expert panel feedback improving its validity. The final version contains 32 side effects with standardized follow-up questions, compatible with any study design and administrable as interview or self-report. It omits less important side effects but includes space for additional symptoms. The SPSI is available in English and German to improve clinical decisions, informed consent, and patient safety.
Psychiatr Res Clin Pract
February 11, 2025
Jules Evans, Marc Aixalà, Brian T Anderson et al.
18 citations
Thirty psychedelic researchers identified critical gaps in knowledge about harms from psychedelic use, including how to define those harms, predict them, and treat them effectively. They recommend better online information, peer support groups, affordable therapy, and psychiatric consultation for people experiencing post-psychedelic difficulties. The researchers also call for improved funding for a psychedelic safety net, suggesting that psychedelic philanthropists, investors, and companies commit 1% of their investment to support safety measures such as research and support services. The article outlines practical steps to make the field of psychedelic medicine safer.
Journal of Psychopharmacology
September 20, 2024
Abigail E. Calder, Benjamin Rausch, Matthias E. Liechti et al.
17 citations
In Switzerland, where psychedelic-assisted therapy (PAT) is permitted under a limited medical use program, patients receiving PAT and healthy volunteers given LSD or psilocybin reported similar overall drug effects and mystical experiences. However, patients reported lower ratings of ego dissolution. Depressive symptoms, measured by the Montgomery-Åsberg Depression Rating Scale, significantly decreased in patients. The strongest predictor of antidepressant improvement was relaxation during the session, while mystical-type experiences did not predict antidepressant effects. Most patients had mild adverse effects that resolved within 48 hours. Hourly assessments of drug effects may better predict clinical outcomes than retrospective measures of mystical experience.
Current Topics in Behavioral Neurosciences
April 29, 2025
Abigail E. Calder, Vincent J Diehl, Gregor Hasler
14 citations
Psychedelic experiences that involve extreme horror, helplessness, or perceived threats can be traumatizing. Such traumatic psychedelic experiences are rare, extreme, and largely preventable, arising from frightening drug effects, unsafe settings, or the emergence of pre-existing trauma. While some people recover quickly, others develop prolonged anxiety, sleep disturbances, derealization, or other trauma-related symptoms. The chapter covers causes, phenomenology, potential outcomes, prevention, and strategies to minimize negative impact.
JAMA Psychiatry
May 31, 2023
Abigail E. Calder, Gregor Hasler
14 citations
Optimizing safety for patients and therapists during psychedelic-assisted psychotherapy requires specific methods. The Viewpoint proposes approaches to enhance safety in this therapeutic context.
Molecular Psychiatry
November 29, 2024
Adrian Hase, Gregor Hasler, Abigail E. Calder
12 citations
A meta-analysis of 29 studies found no evidence that psychoplastogens—including ketamine, LSD, psilocybin, and MDMA—elevate peripheral brain-derived neurotrophic factor (BDNF) levels in humans. The overall effect size was negligible (SMD = 0.024) and not statistically significant. This null result held across different drugs, doses, blood fractions, participant ages, and psychiatric diagnoses. Better-controlled studies showed even smaller effects. The findings suggest that peripheral BDNF may not be a useful biomarker for rapid neuroplasticity changes in humans, or that preclinical findings on psychoplastogen-induced neuroplasticity may not translate to humans. More precise methods, such as neuroimaging, are recommended for future translational research.
Biological Psychiatry Global Open Science
March 1, 2025
Abigail E. Calder, Clifford Qualls, Gregor Hasler et al.
5 citations
The Hallucinogen Rating Scale (HRS) is a widely used questionnaire for measuring subjective effects of psychedelics and other psychoactive drugs. By analyzing 991 questionnaires from 18 studies involving 13 substances, researchers identified 8 factors with good internal consistency that map onto psychedelic effects. The factor model fit the data better than previous models and showed dose responses for most drugs. Patterns on the 8 factors clearly distinguished classic psychedelics (psilocybin, DMT) from dissociatives (ketamine, salvinorin A), empathogens (MDMA), stimulants (methylphenidate, amphetamine), and THC. The meaningfulness factor uniquely differentiated psychedelics from all other substances, supporting the HRS as a psychometrically sound tool for measuring drug-induced altered states.
June 7, 2024
Abigail E. Calder, Gregor Hasler
1 citation
preprint
A new standardized tool, the Swiss Psychedelic Side Effects Inventory (SPSI), was developed to systematically record side effects of psychedelics and MDMA in clinical studies. The SPSI includes 32 side effects with follow-up questions on severity, duration, impact, and treatment-relatedness. It was pilot tested in 145 participants from three studies and refined with expert feedback. The tool is designed for any study design and can be used as an interview or self-report at any time after treatment. Its systematic approach aims to improve clinical decisions, informed consent, and patient safety by providing consistent side effect data.
Journal of Affective Disorders Reports
July 1, 2026
Abigail E. Calder, Vincent J Diehl, Bernd Hinney et al.
People who planned to use serotonergic psychedelics or MDMA in naturalistic settings reported lower neuroticism four weeks later, with the largest reductions in shame and feelings of tension. One week after use, they rated citizenship, family, intimate relationships, and spirituality as more important; only family remained elevated at four weeks. Serotonergic psychedelics were linked to greater increases in spirituality than MDMA. The findings suggest that both types of substances can produce lasting decreases in neuroticism and transient shifts in personal values, with family values showing the most persistent change.
Neuropsychopharmacology
June 18, 2026
Abigail E. Calder, Vincent J Diehl, Morten P. Lietz et al.
A single 100 µg dose of lysergic acid diethylamide (LSD) improved offline motor learning the next day and, one week later, reduced perceived stress and increased aspects of cognitive flexibility in 45 healthy adults. Electroencephalography showed that LSD acutely decreased N1 and P2 auditory event-related potential amplitudes, with P2 still modulated after one week. Transcranial magnetic stimulation revealed increased motor-evoked potential amplitude and faster latency under LSD. Brain-derived neurotrophic factor levels were unchanged. The findings suggest lasting effects of LSD on learning and neural signals, while highlighting challenges in measuring long-term potentiation in humans.
Journal of psychopharmacology (Oxford, England)
May 1, 2026
Vincent J Diehl, Abigail E. Calder, Gregor Hasler
A new questionnaire, the Helioscope Questionnaire, measures how psychedelics such as psilocybin and MDMA alter the processing of traumatic memories during an experience, a process called the helioscope effect. In an online survey of 468 people who had used psychedelics or MDMA, the 21-item scale captured three factors: protection, exposure, and avoidant-distress. A composite score from protection and exposure subscales predicted positive changes in mood and attitude afterward, while avoidant-distress predicted negative changes. Having a trip sitter was linked to stronger protection and exposure scores, and MDMA use was linked to less avoidant-distress. The scale adds a new way to assess therapeutic mechanisms beyond existing measures.
Therapeutic Advances in Psychopharmacology
January 1, 2026
Kristian Beichmann, Polina Catzeflis, Helena Aicher et al.
In Switzerland, physicians provide psychedelic-assisted therapy (PAT) with psilocybin, LSD, or MDMA under case-by-case exemptions from the Federal Office of Public Health. An anonymous survey of 41 physicians found that PAT is used mainly for depression, anxiety, PTSD, and chronic pain. Most physicians work in private practices (82%) and use body-oriented (61%), psychodynamic (59%), and eclectic (54%) approaches. Psilocybin is the most used substance (85%), followed by MDMA (71%) and LSD (65.9%). Substance choice is linked to diagnosis: psilocybin for depression (54%) and substance use disorder (46%), MDMA for PTSD (86%) and anxiety (54%). Music is played in 90% of sessions. Group therapy is common; 42% provide both individual and group settings. Challenges include legal constraints, high patient expectations, and financial barriers.