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Altered states of consciousness

The broad landscape of consciousness that departs from ordinary waking awareness, however induced.

State of the evidence

Synthesized

Synthesized from 25 studies in the library · AI-generated, grounded in the abstracts below

Found by searching the library for Altered states of consciousness, non-ordinary states, altered consciousness, ASC, then ranked by relevance.

Research on altered states of consciousness (ASC) shows they can be reliably measured using standardized psychometric instruments (e.g., the OAV/5D-ASC questionnaire) and are characterized by common dimensions such as oceanic boundlessness, dread of ego dissolution, and visionary restructuralization. Neuroimaging studies indicate that ASCs induced by psychedelics like ayahuasca and LSD involve decreased default mode network activity and connectivity, with effects mediated by the 5-HT2A receptor. While preliminary evidence suggests therapeutic potential for conditions like depression and addiction, the evidence base is dominated by early-stage trials with small samples and open-label designs, limiting confidence in durability and generalizability.

Confidence in the evidence

Low-Moderate
  • Multiple studies (e.g., 17395, 20506) are small (N=29, N=17) and include only one double-blind RCT; others are open-label or observational.
  • Psychometric validation studies (17396, 25868, 28503) are larger (N=393, N=1133, N=777) and support reliable ASC measurement, but the overall clinical evidence base is early-stage.
  • Neuroimaging studies (16728, 19860) are consistent in showing DMN modulation and 5-HT2A receptor involvement, but sample sizes are small (N=10, N=24).
  • Therapeutic findings are promising but preliminary, with durability of effects and long-term safety not well established.
How we rate confidence

Confidence reflects the strength of the underlying evidence, not whether the result is favorable. It weighs the number and size of studies, their design (randomized trials count for more than observational or single-case work), how consistently they point the same way, and their risk of bias.

Tiers run from Insufficient to High. High is rare in this field: small, early, or open-label studies land lower even when their direction is encouraging.

Evidence by study

Direction is each study's finding relative to your question: Supports, Opposes, No effect, Mixed, or Unclear.

Rapid antidepressant effects of the psychedelic ayahuasca in treatment-resistant depression: a randomized placebo-controlled trial 2018
Supports

Ayahuasca produced significant antidepressant effects compared to placebo at days 1, 2, and 7, with large effect sizes.

RCT · Sample size: 29

Psychometric Evaluation of the Altered States of Consciousness Rating Scale (OAV) 2010
Unclear

The OAV questionnaire's 11 lower-order scales were constructed and demonstrated desirable psychometric properties for assessing drug-induced ASC.

psychometric validation

Altered States of Consciousness 1966
Unclear

This theoretical paper integrates knowledge on ASC, discussing conditions for emergence, factors influencing manifestations, common denominators, and adaptive/maladaptive functions.

theoretical

The Standardized Psychometric Assessment of Altered States of Consciousness (ASCs) in Humans 1998
Unclear

ASC are characterized by three oblique dimensions (Oceanic Boundlessness, Dread of Ego Dissolution, Visionary Restructuralization) irrespective of induction method, with satisfactory reliability and validity.

observational · Sample size: 1133

The Subjective Effects of Psychedelics Are Necessary for Their Enduring Therapeutic Effects. 2020
Supports

The paper argues that subjective effects of psychedelics are necessary for their enduring therapeutic benefits, beyond underlying neurobiological mechanisms.

theoretical

Antidepressant effects of a single dose of ayahuasca in patients with recurrent depression: a preliminary report 2015
Supports

Ayahuasca showed fast-acting anxiolytic and antidepressant effects in patients with a depressive disorder.

open-label trial

Antidepressant Effects of a Single Dose of Ayahuasca in Patients With Recurrent Depression 2015
Supports

Ayahuasca administration was associated with significant decreases in depression scores from 80 minutes to day 21 and increased blood perfusion in brain regions implicated in depression.

open-label trial · Sample size: 17

The Psychedelic State Induced by Ayahuasca Modulates the Activity and Connectivity of the Default Mode Network 2015
Supports

Ayahuasca decreased activity and connectivity in the default mode network, supporting the link between ASC and DMN modulation.

observational (fMRI) · Sample size: 10

Psychobiology of Altered States of Consciousness. 2005
Unclear

ASC can be characterized by four dimensions (activation, awareness span, self-awareness, sensory dynamics) and are brought about by compromised brain structure, transient brain dynamics, and neurochemical processes.

review

Changes in global and thalamic brain connectivity in LSD-induced altered states of consciousness are attributable to the 5-HT2A receptor 2018
Supports

LSD reduced associative and increased sensory-somatomotor brain connectivity, and these effects were fully blocked by the 5-HT2A antagonist ketanserin, implicating the 5-HT2A receptor.

RCT · Sample size: 24

Intrinsic Brain Activity in Altered States of Consciousness 2008
Unclear

Altered states of consciousness (e.g., sleep, anesthesia, coma) are associated with systematic impairment of associative frontoparieto-cingulate areas and coherent BOLD fluctuations in the default-mode network.

review

Cardiovascular and neuroendocrine effects and pharmacokinetics of 3, 4-methylenedioxymethamphetamine in humans. 1999
Supports

MDMA significantly increased blood pressure, heart rate, and pupillary diameter, and increased plasma cortisol and prolactin levels.

RCT · Sample size: 8

Short-term autonomic and cardiovascular effects of mindfulness body scan meditation 2006
Supports

Mindfulness body scan meditation increased cardiac respiratory sinus arrhythmia (RSA) compared to relaxation or control, indicating increased parasympathetic activity.

RCT · Sample size: 32

Human Psychopharmacology of Hoasca, A Plant Hallucinogen Used in Ritual Context in Brazil 1996
Supports

Long-term ayahuasca use was associated with remission of psychopathology and no evidence of personality or cognitive deterioration, with high functional status.

observational · Sample size: 30

Ayahuasca-Assisted Therapy for Addiction: Results from a Preliminary Observational Study in Canada 2013
Supports

Ayahuasca-assisted therapy was associated with statistically significant improvements in factors related to problematic substance use.

observational

Therapeutic properties of ayahuasca component N,N-Dimethyltryptamine in a pre-clinical model of Parkinson's disease. 2026
Supports

DMT administration resulted in molecular changes consistent with reduced neuroinflammation and neuronal preservation, and behavioral improvements in a Parkinson's disease model.

preclinical

Beyond Enthusiasm: Ayahuasca and the Future of Depression Research. 2026
Unclear

This paper discusses ayahuasca and the future of depression research, but no specific findings are reported in the abstract.

theoretical

Open MDMA: An Evidence-Based Synthesis, Theory, and Manual for MDMA Therapy Based on Memory Reconsolidation, Complex Systems, and the Defense Cascade 2026
Supports

The paper argues that MDMA therapy durably improves mental illnesses through memory reconsolidation, based on a theoretical model and practical guidance.

theoretical

DMT und Ayahuasca / DMT and Ayahuasca 2026
Unclear

This bilingual full work provides a transdisciplinary scientific overview of DMT and ayahuasca across eight disciplines, with explicit levels of certainty.

review

Registered Clinical Trials of Ayahuasca and DMT: A Scoping Review. 2026
Unclear

Registered clinical trials of ayahuasca and DMT are dominated by early-stage development (phase I), with conservative eligibility criteria and primary outcomes focused on safety and subjective effects.

review

The rhythms of trance: Cultural phenomenology and neural mechanisms of music-induced non-ordinary states of consciousness. 2026
Unclear

Music-induced trance involves partially overlapping neural dynamics, including increased low-frequency synchronization and shifts from executive control to limbic and default mode networks.

review

Global pressure on ayahuasca threatens Amazonian plants and knowledge systems 2026
Unclear

Global pressure on ayahuasca threatens Amazonian plants and Indigenous knowledge systems, highlighting environmental and cultural concerns.

theoretical

EXPANSÃO GLOBAL DA AYAHUASCA E SAÚDE MENTAL 2026
Unclear

The global expansion of ayahuasca presents both psychotherapeutic potentials and psychosocial challenges, requiring respectful exchange with Indigenous knowledge.

theoretical

Koshering Psychedelics: Ayahuasca in the Ultra-Orthodox (Haredi) Jewish World 2026
Mixed

Ayahuasca use among Haredi Jews was primarily therapeutic, with distinct Jewish visionary content and strengthened religious belief, but also religious tensions and strategies to address them.

qualitative · Sample size: 23

Psychometric validation of the French version of the five-dimensional altered states of consciousness questionnaire (5D-ASC) and associated 11 OAV subscales. 2026
Unclear

The French 5D-ASC and 11 OAV subscales showed acceptable psychometric properties, with the 11-subscale solution demonstrating better fit than higher-order structures.

psychometric validation · Sample size: 777

Points of agreement

  • ASC can be reliably measured using standardized psychometric instruments (e.g., OAV/5D-ASC) with common dimensions across induction methods.
  • Psychedelic-induced ASC involve decreased default mode network activity and connectivity, mediated by the 5-HT2A receptor.
  • Preliminary evidence suggests therapeutic potential of ayahuasca for depression and addiction, with fast-acting effects.
  • Long-term ayahuasca use is not associated with cognitive deterioration and may be linked to improved psychological functioning.

Conflicts

  • The role of subjective effects in therapeutic outcomes is debated: one paper argues they are necessary (15637), while others focus on neurobiological mechanisms.
  • Some studies report large effect sizes for ayahuasca's antidepressant effects (17395), but the evidence base is limited by small samples and open-label designs.
  • The global expansion of ayahuasca presents both therapeutic opportunities and risks of cultural appropriation, with differing perspectives on integration.

Gaps

  • Durability of therapeutic effects beyond short-term follow-up (e.g., 7 days, 21 days) is not well established.
  • Most clinical trials are early-phase with small samples and conservative eligibility criteria, limiting generalizability.
  • Blinding and placebo control are challenging in psychedelic research due to the subjective intensity of effects.
  • Long-term safety and potential adverse effects of repeated ayahuasca use are not systematically studied.
  • The role of set, setting, and cultural context in shaping ASC outcomes is acknowledged but not rigorously controlled across studies.
Browse these studies in the library
How we analyze this

This synthesis reads the 15 most-cited and 10 most recent studies whose primary subject is Altered states of consciousness, up to 25 in all. The most-cited set anchors the established evidence, and the recent set surfaces work that is too new to have gathered citations yet.

A study qualifies only when Altered states of consciousness or a known alias appears in its title or keywords, so broad reviews that mention it only in passing are left out. Each study is read from its abstract, strongest evidence first, and the summary reports the direction of the results along with any conflicts and gaps.

Ask your own question in the Research Synthesis Tool

1,186 articles · 412 from the last two years · 109,146 participants across 346 studies reporting sample size

Common study designs

review 181 experimental study 33 observational study 48 observational cohort 73 theoretical or philosophical paper 250

Research

Synthesize the evidence → Search all →

Shared Neurobiological and Computational Mechanisms of Psychedelic, Contemplative, and Fasting-Induced Mystical Experience

Alex Jinich-Diamant preprint

Mystical states induced by psychedelics, meditation, or fasting all converge on the same brain state: a transient near-critical regime. Serotonergic psychedelics relax top-down priors by sensitizing layer 5 pyramidal neurons; open-monitoring meditation elevates cortical entropy through altered thalamocortical connectivity; caloric restriction destabilizes the default mode network by attenuating metabolic support for high-level attractors. The depth of the mystical state, not the method of induction, predicts lasting therapeutic benefit, suggesting conscious experience itself is the mechanistic agent of change. This framework proposes that near-critical dynamics may allow field-theoretic and quantum-coherent contributions to consciousness to become detectable.

DOI: 10.31234/osf.io/km8hr_v2

Classical Processing of Primary Delusional Experiences in a Family with Shared Delusion and Trance Possession Attacks – A Case Report

Research Square • Amit Kumar

A 24-year-old woman experienced possession trance attacks, a condition involving altered consciousness where a person's identity is replaced by a spirit or deity, with amnesia for the event. Her entire family developed shared delusional beliefs, and multiple members also had possession attacks over time. Such attacks can be misdiagnosed as psychotic illnesses like schizophrenia. The case highlights the cultural and familial context of possession trance, which must cause distress or impairment and not be due to psychosis or substance use.

DOI: 10.21203/rs.3.rs-4313326/v1

Altered states of Ganzfeld: A systematic review

Anney Roy

A systematic review of controlled trials on the Ganzfeld experiment, which uses dim light and static sound to create a uniform perceptual field, found that only four such studies were conducted between 2000 and 2022. The review confirms that alpha brainwave interactions are involved in hallucination-like imagery during Ganzfeld stimulation. The authors highlight a significant gap in research on Ganzfeld-induced altered states of consciousness.

DOI: 10.22541/au.166618485.54479783/v1

Implicit-explicit gradient of nondual awareness or consciousness as such

Zoran Josipovic • 5 citations

Consciousness is often depicted with a two-dimensional map: levels or states on one axis and phenomenal contents on the other. This conflates content with awareness, hindering scientific understanding. The author proposes adding a third dimension—an implicit-explicit gradient of nondual awareness, a basic non-conceptual awareness free of subject-object fragmentation. This addition clarifies everyday dualistic experiences and is especially relevant for understanding unitary and nondual experiences from contemplative practices, substances, or spontaneous occurrences. The proposal is discussed in relation to current theories of consciousness.

DOI: 10.31231/osf.io/ngupr

Early and Contemporary Human Neuroimaging Studies of Serotonergic Psychedelics

Preprints.org • Enzo Tagliazucchi • 2 citations preprint

Serotonergic psychedelics alter conscious awareness, perception, mood, emotion, and cognition, but their effects resist simple classification like stimulant or sedative. Their defining feature is temporarily inducing an altered state of consciousness. Because only humans can explicitly report conscious experiences, studying these compounds requires non-invasive neuroimaging techniques in healthy subjects. This review examines how neuroimaging has been applied to investigate the neural correlates of altered consciousness caused by serotonergic psychedelics.

DOI: 10.20944/preprints202005.0510.v1

The Bodily Self from Psychosis to Psychedelics

Amir Harduf, Roy Salomon preprint

The sense of self, normally experienced as unified and embodied, can be altered in psychosis and by psychedelic compounds. Using the Moving Rubber Hand Illusion with 75 participants—psychosis patients, people with substantial psychedelic experience, and controls—the study found that psychosis patients had reduced Body Ownership and Sense of Agency during volitional action. The psychedelic group reported subjective long-lasting changes to the sense of self, but no differences between control and psychedelic participants were found. The results suggest that psychedelics induce acute and enduring subjective changes in the sense of self that are not manifested at the level of the bodily self, while bodily self-processing related to volitional action is disrupted in psychosis.

DOI: 10.31234/osf.io/5e4q6

Neurophenomenology of Out-of-Body experiences induced by hypnotic suggestions

Enrico Facco, Edoardo Casiglia, Benedikt Emanuel Al Khafaji et al. preprint

Out-of-body experiences (OBEs) induced through hypnosis (H-OBEs) produce stronger phenomenological changes than those induced through imagination alone. In 15 highly hypnotizable participants, H-OBEs led to significantly higher scores on the Altered State, Positive Affect, Altered Experience, and Attention subdimensions of the Phenomenology of Consciousness Inventory, alongside a decrease in beta and gamma band power in right parieto-temporal brain regions. These findings suggest that hypnotically induced OBEs may serve as a useful model for studying genuine OBEs, involving altered multisensory integration in right parieto-temporal areas.

DOI: 10.31234/osf.io/6a4hc

Ketamine-induced pleasant but not unpleasant dissociation is linked to the functional connectivity profile of the posteromedial cortex

Zumrut Duygu Sen, Nitin Sharma, Lena Vera Danyeli et al. preprint

Ketamine causes temporary dissociative experiences alongside its rapid therapeutic effects. This study examined whether pleasant and unpleasant dissociations can be predicted by functional connectivity of the posteromedial cortex (PMC) in 35 male participants during ultrahigh-field MRI. Pleasant dissociation (oceanic boundlessness) was predicted by PMC connections with control network regions at baseline and during infusion, and additionally with default mode network regions during infusion. Unpleasant dissociation (anxious ego dissolution) could not be predicted by PMC connectivity. The findings suggest distinct brain mechanisms for pleasant versus unpleasant dissociations, and that PMC connectivity changes may be a shared neural feature of dissociation from both ketamine and psychedelics.

DOI: 10.31234/osf.io/eadr2

Brain State Dynamics in Ketamine-Induced Dissociation Resemble Those in PTSD

Noam Goldway, Taly Markovits, Naomi Fine et al. preprint

Dissociation—feeling detached from one's body, surroundings, or self—is common in PTSD but its neural basis is poorly understood. Using network control theory, researchers examined brain dynamics during dissociative states in two contexts: ketamine-induced dissociation in 30 healthy volunteers and therapeutic interventions in 78 PTSD patients. Ketamine produced brain dynamics similar to those seen in PTSD patients before treatment, with increased dominance of a default mode network meta-state and decreased dominance of a somatomotor meta-state. Ketamine did not significantly alter the brain's energetic landscape, but transition energies increased after PTSD treatment, suggesting more organized, less entropic brain dynamics.

DOI: 10.31234/osf.io/v52qb

Born Twice DMT and the Echo of Our First Conscious Experience

Tony Montgomery

A simple endogenous tryptamine can profoundly alter perception and self-modeling. The Birth Echo Hypothesis proposes that during a narrow perinatal window around delivery, a convergence of stress, sensory novelty, and neuromodulators biases encoding of high-salience sensorimotor templates. In adulthood, exogenous DMT may reconfigure brain dynamics via 5-HT2A and sigma-1 receptors, making these preverbal templates accessible as archetypal, emotionally intense, synesthetic content. DMT is framed as a co-modulator within an evolved perinatal regulatory ensemble. Testable predictions include adult DMT phenomenology showing perinatal-consistent motifs, neonatal EEG/fMRI state-space similarity to adult DMT states, and peri-parturient biospecimens revealing DMT-pathway marker co-variation. The hypothesis reframes psychedelic phenomenology as structural re-expression of early sensorimotor templates.

DOI: 10.31124/advance.175748232.23223560/v1

Clinical trials

All Altered states of consciousness trials →