Frontiers in Psychology
July 2, 2018
Timo Torsten Schmidt, Hendrik Berkemeyer
75 citations
A new database, the Altered States Database (ASDB), compiles questionnaire data from research articles on experimentally induced altered states of consciousness (ASC). It includes data from MEDLINE-listed journals where ASCs were induced by pharmacological (e.g., psychoactive drugs) or non-pharmacological methods (e.g., breathing techniques, sensory deprivation) and assessed with standardized questionnaires. The database enables direct comparisons of psychological effects across different induction methods and supports meta-analyses to establish dose-response relationships specific to each method.
Therapeutic Advances in Psychopharmacology
January 1, 2023
Ricarda Evens, Tomislav Majić, Timo Torsten Schmidt et al.
49 citations
A systematic review of 48 studies involving 1,774 participants found that classic serotonergic psychedelics (LSD, psilocybin, DMT, 5-MeO-DMT, mescaline, or ayahuasca) produce a characteristic pattern of subacute effects lasting from one day to one month after use. These include reductions in psychopathological symptoms, increases in wellbeing, mood, mindfulness, social measures, spirituality, and positive behavioral changes, along with mixed changes in personality and creativity. Subacute adverse effects included headaches, sleep disturbances, and individual cases of increased psychological distress, but no serious adverse events were reported. The findings support the existence of a 'psychedelic afterglow' phenomenon that may enhance psychotherapeutic interventions.
PLoS ONE
July 1, 2021
Marie Therese Bartossek, Johanna Kemmerer, Timo Torsten Schmidt
43 citations
Flickering light with closed eyes temporarily alters consciousness, producing simple visual hallucinations like colors and geometric patterns. In 24 participants, 10 Hz stimulation caused stronger effects than 3 Hz, including vivid visual hallucinations. Participants' Absorption personality trait strongly correlated with the intensity of altered consciousness. The effects were rated similar in strength to those from psychedelic substances, supporting the study of shared brain mechanisms.
PLoS ONE
March 16, 2022
Katharina Dworatzyk, Tallulah Jansen, Timo Torsten Schmidt
19 citations
Two self-report questionnaires for assessing psychedelic experiences, the Challenging Experience Questionnaire and the Ego-Dissolution Inventory, were translated into German and evaluated in an online survey. The German version of the Challenging Experience Questionnaire showed acceptable fit to the original 7-factor structure, good internal consistency, and convergent validity with measures of anxiety and altered states of consciousness. The German Ego-Dissolution Inventory did not support the original single-factor structure; exploratory analysis suggested a 5-item version that measured ego-dissolution with high internal consistency and convergent validity. These validated translations help standardize assessment in psychological and neuroscientific research on altered states of consciousness.
Neuroscience and biobehavioral reviews
August 1, 2025
Larry Douglas Fort, Cyril Costines, Marc Wittmann et al.
14 citations
A review of classification schemes for altered states of consciousness (ASCs) groups them into three types: those based on subjective experiences (state-based), those based on induction methods (method-based), and those based on neurophysiological mechanisms (neuro/physio-based). Comparing and extending these schemes can improve identification of neural correlates of consciousness and inform clinical research. The authors cluster concepts from state-based schemes to help quantify core ASC phenomenology for basic and clinical studies.
Journal of Psychopharmacology
March 4, 2021
Tomislav Majić, Meike Sauter, Felix Bermpohl et al.
14 citations
An online survey of 386 mostly well-educated individuals who had used Kambô, the secretion of the Giant Maki Frog, found that motivations included general healing, detoxification, and spiritual growth. Acute effects involved severe physical reactions and mild psychoactive experiences, with 41.97% reporting a feeling of connection to the frog's spirit. Most participants (87.31%) reported increased well-being or life satisfaction, and 64.26% considered Kambô of high spiritual significance. Few reported lasting physical (2.85%) or mental (1.81%) health problems attributed to Kambô. The authors note that further research is needed to understand how setting and expectations influence reported effects.
Frontiers in Psychology
February 14, 2024
Caspar Montgomery, Timo Torsten Schmidt, Ioanna Amaya
13 citations
Flicker light stimulation (FLS), a non-pharmacological method that induces altered states of consciousness (ASCs) and hallucination-like phenomena, can enhance emotional responses to music. In a study with twenty participants, listening to emotionally evocative music while undergoing FLS significantly increased reported music-evoked emotion, particularly emotions related to “Joyful Activation.” The intensity of the FLS experience correlated with higher levels of emotional arousal. These results suggest that FLS may serve as a method for inducing ASCs and that visual stimulation can interact with music-evoked emotion, paralleling effects seen with classic psychedelics like LSD.
Scientific Reports
December 9, 2020
Timo Torsten Schmidt, Simon Reiche, Caroline L. C. Hage et al.
12 citations
Kambô, the secretion of the Amazonian Giant Leaf Frog, contains many bioactive peptides and was traditionally used by indigenous Amazonian communities as medicine to improve hunting. In Western urban healing circles, its use has spread over the past 20 years. This retrospective study assessed psychological effects in 22 anonymous users using standardized questionnaires for altered states of consciousness. Acute effects were mild to moderate, with no psychedelic-type perceptual or thinking distortions. Persisting effects were predominantly positive, with high scores on personal and spiritual significance.
Fortschritte der Neurologie · Psychiatrie
July 1, 2017
Tomislav Majić, Henrik Jungaberle, Timo Torsten Schmidt et al.
10 citations
The use of serotonergic hallucinogens (psychedelics) such as LSD and psilocybin, and entactogens such as MDMA, in psychotherapy has recently gained increasing scientific interest. This review summarizes current evidence on substance-assisted psychotherapy with serotonergic psychoactive substances. A selective literature search in PubMed and the Cochrane Library identified studies since 2000 examining these substances in psychotherapy. Indications studied include alcohol dependence (LSD and psilocybin), nicotine dependence (psilocybin), anxiety and depression in life-threatening physical illness (LSD and psilocybin), obsessive-compulsive disorder (psilocybin), treatment-resistant major depression (psilocybin), and post-traumatic stress disorder (MDMA). Dependence disorders, PTSD, and anxiety and depression in life-threatening physical illness are the best-evaluated indications. Evidence suggests efficacy with relatively good tolerability, but further studies are needed to assess these substances as future options for certain treatment-resistant mental disorders.
Current topics in behavioral neurosciences
December 31, 2024
Cyril Costines, Timo Torsten Schmidt
8 citations
Psychedelic substances produce a wide range of effects on perception, cognition, and emotion, collectively called "psychedelic phenomenology." There is no agreement on which altered features, such as hallucinations or ego dissolution, define a "psychedelic state." This chapter reviews commonly discussed core features of psychedelic experiences, focusing on recent quantitative assessment methods rather than earlier phenomenological work. It also addresses under-researched distressing effects, or "challenging experiences" ("bad trips"), highlighting their importance for understanding therapeutic potential and risks. Historically, psychedelic phenomenology links to psychopathology. Refining assessment of distressing effects is stressed to identify factors promoting beneficial acute experiences and limiting potentially harmful long-term effects.
bioRxiv (Cold Spring Harbor Laboratory)
June 11, 2020
Tim Hirschfeld, Timo Torsten Schmidt
8 citations
preprint
Psilocybin, the active component of magic mushrooms, produces subjective experiences that vary with dose. A meta-analysis of data from the Altered States Database examined dose-response relationships for three standardized questionnaires: the Altered States of Consciousness Rating Scale, the Mystical Experience Questionnaire (MEQ30), and the Hallucinogen Rating Scale (HRS). Ratings on most dimensions and subscales correlated positively with psilocybin dose. Because individual differences and environmental factors also influence subjective experiences, these findings from controlled laboratory experiments may not generalize to recreational use. The analysis provides a reference for expected subjective effects in experimental and clinical psilocybin research.
Journal of Psychopharmacology
March 31, 2025
Tomislav Majić, Timo Torsten Schmidt, Anna Gröticke et al.
4 citations
A new questionnaire called the Afterglow Inventory (AGI) reliably measures pleasant psychological effects that can occur days after a psychedelic experience, such as with psilocybin or LSD. The AGI captures five distinct dimensions: vitality, transpersonal aspects, inspiration/creativity, interpersonal relationships, and relationship to nature. In an international online survey of 1,323 people who had recently used a psychedelic and 157 controls, the AGI successfully distinguished between the two groups. Stronger and more positive acute psychedelic experiences were associated with higher afterglow scores. This tool may help researchers understand how short-term afterglow effects connect to longer-term therapeutic outcomes.
bioRxiv (Cold Spring Harbor Laboratory)
November 7, 2022
Tim Hirschfeld, Johanna Prugger, Tomislav Majić et al.
4 citations
preprint
Lysergic acid diethylamide (LSD) produces a sigmoid-like increase in altered states of consciousness, with effects plateauing around 100 micrograms. The strongest changes involve perception and illusory imagination, followed by positively experienced ego-dissolution, while anxiety and dread of ego dissolution show only small effects. Considerable variability in responses highlights the importance of non-pharmacological factors. These dose-response relationships can serve as references for future research on LSD.
February 22, 2023
Madlen Peters, Johanna Prugger, Petar Radoev Dimkov et al.
3 citations
preprint
The Altered States Database (ASDB) is an open science project that compiles psychometric questionnaire data on altered states of consciousness experiences induced by various methods. This update reports a systematic literature review following PRISMA guidelines, where 431 items were screened and data from 23 eligible journal articles were extracted, covering literature up to December 31, 2022. The complete dataset is publicly available on the Open Science Framework.
April 2, 2021
Katharina Dworatzyk, Tallulah Jansen, Timo Torsten Schmidt
3 citations
preprint
The German versions of two questionnaires measuring psychedelic experiences—the Challenging Experience Questionnaire (CEQ) and the Ego-Dissolution Inventory (EDI)—were evaluated in an online survey. The CEQ's seven-factor structure was confirmed, with good internal consistency and no differences by gender or prior anxiety or depression. Correlations with other scales supported its convergent validity. However, the EDI's single-factor structure was not confirmed; exploratory analysis suggested a five-item version with high internal consistency and convergent validity. These validated German tools help standardize research on altered states of consciousness.
June 4, 2023
Timo Torsten Schmidt, Cyril Costines, Enzo Tagliazucchi et al.
2 citations
preprint
The Altered Xperience Project (AXP) is an open citizen science initiative that systematically collects data on subjective experiences from consciousness-manipulating techniques, including psychoactive substances and non-pharmacological methods. A proof-of-principle dataset (v1.0) includes data collected through May 2022, with most gathered between October 3 and 13, 2022. The dataset covers low, medium, and high doses of alcohol, cannabis, NMDA, and psilocybin. Participants were recruited internationally via social media by the citizen science group El gato y la Caja, and participation was incentivized with an infographic comparing individual data to others. The data is publicly available on the Open Science Framework.
October 22, 2024
Tomislav Majić, Timo Torsten Schmidt, Anna Gröticke et al.
1 citation
preprint
A new questionnaire called the Afterglow Inventory (AGI) was developed and validated to measure the pleasant, temporary psychological effects that sometimes follow the acute phase of a psychedelic experience. An international online survey of 1,323 people who had taken a psychedelic and 157 who had taken a non-psychedelic substance in the past four weeks identified five key factors: vitality, transpersonal aspects, inspiration/creativity, interpersonal relationships, and relationship to nature. The 24-item AGI successfully distinguished psychedelic users from controls, and its overall score was positively correlated with the intensity and positive valence of the acute effects. The AGI may help researchers better understand how acute, subacute, and long-term effects of psychedelics relate to each other.
December 13, 2024
Trevor Hewitt, Ioanna Amaya, Romy Beauté et al.
preprint
Exposure to rapid and bright stroboscopic light can induce vivid visual hallucinations of color and geometric forms, a phenomenon first documented by Purkinje over 200 years ago. Despite centuries of scientific, therapeutic, and cultural interest, fundamental questions remain about its phenomenology, physiological origins, and potential clinical applications. This narrative review summarizes the historical research on stroboscopic light stimulation, its use in recreational and lay-therapeutic settings, and discusses the phenomenology of these experiences. It also examines current perspectives on the neural mechanisms that may underlie stroboscopically induced experiences and outlines directions for future research.
May 3, 2024
Kasey Devitt, Johanna Prugger, Tim Hirschfeld et al.
preprint
The Altered States Database (ASDB) is an open data initiative that collects psychometric questionnaire data on subjective experiences from pharmacologically and non-pharmacologically induced altered states of consciousness. The current update adds data published in 2023, identified through a systematic literature review following PRISMA guidelines. Of 454 items screened, 13 journal articles were included: ten report on the 11-ASC, eight on the 5D-ASC, six on the MEQ-30, and one on the PCI. The ASDB now contains data on 22 substances and 13 techniques, from 198 journal articles and 847 datasets, accessible online.
bioRxiv (Cold Spring Harbor Laboratory)
July 24, 2020
Timo Torsten Schmidt, Simon Reiche, Caroline L. C. Hage et al.
preprint
Kambô, the secretion of the Giant Leaf Frog (Phyllomedusa bicolor), is ritually used by Amazonian ethnicities against bad luck in hunting and has spread to Western urban centers, often alongside ayahuasca. A retrospective study of 22 anonymous users (mean age 39 years, 45.5% female) assessed acute and subacute psychological effects with standardized questionnaires. Acutely, participants reported mild to moderate psychological effects without psychedelic-type perceptual or thinking distortions. Persisting effects were predominantly positive and pleasant, with surprisingly high personal and spiritual significance. Subacute and long-term effects overlapped with the 'afterglow' phenomena following serotonergic psychedelics.