The administration of serotonergic hallucinogens can induce profound alterations in human consciousness, ranging from ecstatic mystical states to harrowing episodes of psychological terror. When an individual experiences overwhelming anxiety, acute paranoia, somatic dread, or the terrifying sensation of impending madness under the influence of hallucinogenic substances, the phenomenon is colloquially termed a bad trip. In modern neuropsychopharmacology and clinical psychiatry, this acute adverse psychological event is recontextualized as a challenging psychedelic experience, recognizing both its clinical risks and its potential for subsequent psychological integration.
Bad Trip (Challenging Psychedelic Experience)
1. Concise Definition
A bad trip is an acute, temporary adverse psychological reaction precipitated by the ingestion of psychedelic substances, characterized by profound anxiety, terror, existential dread, paranoia, confusion, and feelings of loss of control or impending dissolution of the self. Clinically conceptualized as an acute hallucinogen-induced dysphoric reaction or challenging psychedelic experience, it represents an intense perturbation of cognitive, perceptual, and affective processing.
Rather than denoting a toxicological overdose in the physiological sense, a bad trip is primarily an intrapsychic and somatic crisis. The subject experiences an overwhelming mismatch between their psychological defense mechanisms and the unconstrained, hyper-associative mental state elicited by the psychoactive agent. Although physiologically benign in the vast majority of cases involving pure classical psychedelics, the intense subjective distress can lead to acute behavioral dysregulation, hazardous misinterpretations of sensory reality, and prolonged psychological distress if not managed with competent psychological harm reduction or clinical support.
Within modern psychedelic-assisted psychotherapy, clinicians increasingly distinguish between purely counter-therapeutic panic episodes and difficult, emotionally challenging experiences that ultimately facilitate therapeutic breakthroughs. While colloquial discourse frequently views bad trips as purely negative anomalies, contemporary psychological frameworks conceptualize them as dynamic, dose-dependent, and context-dependent manifest processes governed heavily by extrapharmacological variables.
2. Etymology & Linguistic Origin
The term bad trip emerged from mid-twentieth-century American counterculture and underground drug vernacular during the rapid proliferation of recreational lysergic acid diethylamide usage in the 1960s. The noun trip had already entered informal American English in the late 1950s and early 1960s to describe the prolonged temporal trajectory and narrative quality of an altered state of consciousness, conceptualizing the multi-hour pharmacological episode as a metaphorical journey through inner space.
The compounding of the qualitative adjective bad with trip arose to distinguish benign, euphoric, or transcendental drug states from terrifying, dysphoric, or disorienting reactions. Early documentation of the term in underground print journalism and psychiatric literature began appearing in 1965 and 1966, notably in studies examining emergency room admissions in San Francisco and New York. Clinicians quickly adopted the colloquialism to describe what medical literature had previously classified as acute hallucinogen-induced psychotic reactions, toxic psychosis, or adverse hallucinogen reactions.
In contemporary academic discourse and clinical trials conducted under the auspices of contemporary regulatory agencies, researchers predominantly substitute the colloquial label with terms such as challenging experience, acute psychedelic distress, or acute dysphoric hallucinogen episode. This linguistic shift reflects a deliberate effort to avoid the deterministic, stigmatizing implications of the word bad, highlighting instead that distress during an altered state may constitute a therapeutically meaningful confrontation with repressed psychological material rather than an insurmountable medical failure.
3. Pronunciation & Grammatical Form
In standard English, the term is pronounced as two distinct monosyllabic words: /bæd trɪp/. The lexical stress resides equally or slightly predominates on the noun, reflecting a standard compound noun phrase pattern. It functions primarily as a countable compound noun, taking the plural form bad trips.
In colloquial and informal register, the phrase has also generated an idiomatic adjective phrase (e.g., bad-tripping, functioning as a present participle to describe the active state of undergoing the crisis) and can occasionally be found in metaphorical, non-pharmacological contexts to describe any nightmarish, disorienting, or deeply unpleasant real-world ordeal. In formal clinical and research writing, however, the term is enclosed in quotation marks or replaced entirely with formal diagnostic descriptors such as acute hallucinogen-induced dysphoria or challenging psychedelic experience.
4. Detailed Conceptual Explanation
To fully grasp the scope and boundaries of a bad trip, one must examine the intersection between neurochemical disruption and psychological defense architecture. Classical psychedelics—including lysergic acid diethylamide (LSD), psilocybin, dimethyltryptamine (DMT), and mescaline—exert their core neuropharmacological actions through agonism at serotonin 5-HT2A receptors, particularly those located on cortical pyramidal cells in layer V of the prefrontal cortex. This pharmacodynamic action dismantles the hierarchical predictive processing of the brain, leading to functional hyperconnectivity, increased cortical entropy, and the profound disintegration of the default mode network (DMN).
Under ordinary waking conditions, the default mode network maintains the coherent boundary of the ego, organizing autobiographical memory, temporal continuity, and self-other distinctions. When this network undergoes acute pharmacological decoupling, the individual experiences ego dissolution. If the individual embraces this dissolution with trust and psychological flexibility, the result is frequently described as an oceanic, mystical, or unitive experience. Conversely, if the individual interprets the dissolution of egoic boundaries as biological death, permanent cognitive insanity, or total loss of physical agency, the psychological system initiates an acute resistance response, triggering catastrophic panic.
The subjective landscape of acute psychedelic distress encompasses several interrelated cognitive and affective domains. Chrono-perceptual distortions are ubiquitous: time may appear to decelerate completely, freeze, or loop indefinitely, creating the terrifying illusion that the dysphoric state will persist for eternity. Cognitive loops emerge, in which the subject becomes trapped in repetitive, agonizing cycles of circular reasoning, obsessive existential questioning, or intrusive guilt. Paranoia frequently develops, wherein the environment, co-users, facilitators, or physical objects are misattributed as hostile, deceptive, or threatening.
Furthermore, acute somatic sensations exacerbate cognitive distress. Dysregulated autonomic arousal—manifesting as tachycardia, diaphoresis, hyperventilation, tremors, gastrointestinal distress, and profound muscle tension—is misappraised by the dysregulated predictive brain as catastrophic physiological failure. The individual enters a feed-forward neurovisceral loop: bodily anxiety generates cognitive panic, which in turn spikes sympathetic nervous system output, reinforcing the subjective conviction that death or somatic destruction is imminent.
Crucially, the boundaries of a bad trip must be distinguished from organic toxic encephalopathies, acute chemical neurotoxicity, and genuine permanent psychoses. In a classical psychedelic-induced challenging state, the underlying physiological integrity of the vital organs remains stable, and the psychological decompensation is directly linked to the pharmacokinetics of the compound. As the drug plasma concentration falls and receptor occupancy declines, the intense psychological symptoms resolve, leaving the individual in a state of exhaustion, relief, and subsequent cognitive processing.
5. Historical Development
Adverse reactions to naturally occurring hallucinogens have been documented for millennia across ethnobotanical and indigenous traditions. In traditional Amazonian, Mesoamerican, and African healing contexts, frightening visions, spiritual combat, and profound somatic distress during visionary rituals were rarely pathologized as errors. Instead, indigenous epistemologies interpreted intense distress as essential purification, shamanic death-and-rebirth crises, or direct encounters with challenging spiritual entities that required ritual songs (such as icaros), tobacco purifications, and the steady guidance of an experienced curandero.
The modern scientific conceptualization of adverse psychedelic episodes began in the 1940s and 1950s following Albert Hofmann’s 1943 synthesis and accidental ingestion of LSD-25 at Sandoz Laboratories. Hofmann himself documented what can be considered the first recorded modern bad trip during the peak of his famous bicycle ride, experiencing acute paranoia that his neighbor was a malevolent witch and terror that he was drifting into complete insanity or biological death before the experience stabilized into tranquil euphoria.
During the 1950s, early psychiatric research spearheaded by figures like Humphry Osmond, Abram Hoffer, and later Stanislav Grof began investigating LSD, mescaline, and psilocybin. Osmond coined the term psychedelic in 1956 specifically to move beyond early paradigms that labeled these substances psychotomimetic (psychosis-mimicking). In the 1960s, researchers such as Timothy Leary and Richard Alpert formulated the foundational concept of set and setting, demonstrating that terrifying adverse reactions were not fixed pharmacological properties of the molecules, but rather emergent interactions between internal psychological expectations (set) and the surrounding physical and social environment (setting).
The uncontrolled proliferation of hallucinogen consumption during the late 1960s led to a surge in emergency room admissions, fueling sensationalized media accounts of bad trips involving homicidal behavior, accidental defenestration, and irreversible brain damage. This cultural backlash directly contributed to the passage of the United States Controlled Substances Act of 1970 and the 1971 United Nations Convention on Psychotropic Substances, effectively halting mainstream clinical research for nearly three decades.
The psychedelic renaissance of the late 1990s and 2000s, pioneered by researchers such as Roland Griffiths at Johns Hopkins University, Franz Vollenweider in Switzerland, and David Nutt and Robin Carhart-Harris at Imperial College London, systematically revived empirical inquiry. Researchers developed standardized psychometric batteries to measure challenging episodes, introduced rigorous protocols for screening and preparation, and established specialized psychedelic harm reduction teams (such as the Zendo Project) at mass public gatherings, transforming the clinical and cultural handling of acute psychedelic crises.
6. Theoretical Foundations
The academic understanding of acute hallucinogen distress rests on multiple interlocking theoretical frameworks across neuroscience, cognitive psychology, psychoanalysis, and transpersonal psychology.
From a neurocomputational perspective, the REBUS model (Relaxed Beliefs Under Psychedelics) formulated by Robin Carhart-Harris and Karl Friston provides a compelling explanation. Based on the free-energy principle and predictive coding, the REBUS framework posits that 5-HT2A receptor stimulation downweights the precision of high-level prior beliefs (priors) encoded in the default mode network and higher cortical hierarchies. Consequently, raw, unconstrained bottom-up sensory and affective information floods conscious awareness. If the individual’s lower-level affective inputs carry high loads of repressed trauma, dread, or somatic panic, and the higher-order cognitive schemas are unable to exert top-down inhibitory control or rational contextualization, the cognitive system descends into catastrophic entropy, manifesting subjectively as an acute bad trip.
From a transpersonal and psychodynamic orientation, Stanislav Grof’s cartography of the unconscious provides an influential clinical framework. Grof posited that psychedelic substances act as non-specific amplifiers of the human psyche. When high doses destabilize personal biographical defenses, consciousness descends into what Grof termed Basic Perinatal Matrices (BPMs). Specifically, Grof linked severe bad trips to BPM II (the stage of biological labor where contractions have begun but the cervix remains closed), characterized by visceral sensations of being trapped in an inescapable, eternal cosmic hell, suffocating, or suffering divine abandonment. In Grofian theory, acute distress is not an irrelevant side effect, but the experiential manifestation of deep psychological birth trauma or ancestral material seeking energetic release.
Cognitive and emotional regulation theories emphasize psychological flexibility and experiential avoidance, as operationalized in Acceptance and Commitment Therapy (ACT). According to this perspective, a bad trip is actively sustained by experiential avoidance—the futile, desperate struggle to suppress, eliminate, or escape undesirable internal thoughts, sensations, and hallucinations. The harder the individual fights against the unfolding psychedelic effects, the more intensely the perceptual system registers a state of extreme mortal danger, escalating panic into full-blown emotional decompensation.
7. Key Components, Types & Dimensions
Acute psychedelic distress is multidimensional rather than homogeneous. Factor-analytic research identifies several distinct, co-occurring components:
- Acute Panic and Loss of Agency: A catastrophic surge of autonomic terror driven by the perceived inability to control thoughts, bodily functions, or the flow of sensory experience.
- Ego-Dissolution Terror: The horrifying subjective sensation of psychological fragmentation, personality annihilation, or physical death, occurring in the absence of spiritual acceptance.
- Paranoid and Persecutory Ideation: The conviction that external companions, medical personnel, or unseen forces are conspiring to harm, interrogate, poison, or permanently institutionalize the user.
- Time Dilation and Temporal Trapping: The severe distortion of subjective time perception, leading to the agonizing cognitive conviction that the painful experience is eternal and that return to baseline sobriety is impossible.
- Cognitive and Thought Loops: Highly repetitive, circular reasoning patterns in which the subject obsessively retraces the same catastrophic thought, sentence, or memory without achieving resolution.
- Somatic Dread and Visceral Dysphoria: Distressing bodily symptoms, including perceived respiratory arrest, cardiac palpitations, muscle rigidity, nausea, and severe perceptual distortions of internal organs.
- Existential and Metaphysical Guilt: Sudden, overwhelming exposure to feelings of profound unworthiness, moral failure, cosmic isolation, or existential despair.
8. Examples & Illustrative Cases
To understand the clinical manifestation of these theoretical constructs, consider the following illustrative cases representing recreational and clinical contexts:
Case 1: The Recreational Set-and-Setting Failure. A 21-year-old college student ingests an unmeasured dose of illicitly acquired LSD at a crowded, chaotic music festival with unfamiliar acquaintances. Two hours post-ingestion, the sensory environment becomes overwhelming. The individual misinterprets a passing security guard as an operative sent to arrest them. They attempt to flee, become hyperventilating and disoriented, and rapidly develop a cognitive loop: “I took too much, I broke my brain, I can never go home.” They perceive subjective time as stopped, believing they have permanently destroyed their sanity. Without calm de-escalation, the subject exhibits acute psychomotor agitation, shouting for help until festival medical staff guide them to a quiet psychedelic harm reduction tent. Through calm verbal grounding, reassurance of pharmacological safety, and physical warmth, the panic subsides over three hours without pharmacotherapy.
Case 2: The Therapeutic Deep-Material Crisis. A 45-year-old participant in an approved clinical trial of psilocybin-assisted psychotherapy for major depressive disorder receives a 25 mg dose of pure psilocybin. Three hours into the session, the participant suddenly rips off their eyeshades in terror, weeping uncontrollably and reporting crushing chest tightness. The participant reports seeing visions of an abusive childhood event long repressed, feeling that the room is collapsing and expressing the absolute conviction that they are dying. Rather than attempting to suppress the emotion, the two trained therapists utilize established clinical guidelines: they offer gentle physical contact (holding a hand with prior consent), encourage the participant to lie back down, breathe deeply, and surrender directly into the frightening feelings rather than fleeing them. Within forty minutes, the terror transforms into profound catharsis, followed by feelings of forgiveness and psychological release. What began as an acute bad trip resolved into the central therapeutic breakthrough of the patient’s treatment.
9. Measurement & Assessment
Assessing the acute dynamics and long-term sequelae of challenging psychedelic states requires validated, psychometrically sound measurement instruments. Historically, researchers relied on general psychiatric scales such as the Brief Psychiatric Rating Scale (BPRS) or state anxiety inventories. However, these tools fail to capture the unique phenomenology of altered states of consciousness.
The premier psychometric instrument developed specifically to quantify acute adverse psychedelic states is the Challenging Experience Questionnaire (CEQ), validated by Katherine MacLean, Roland Griffiths, and colleagues in 2016. The CEQ is a 26-item self-report questionnaire administered post-session, comprising seven distinct subscales: Grief, Fear, Death, Insanity, Isolation, Physical Distress, and Paranoia. Empirical validation demonstrates that the CEQ successfully differentiates purely traumatizing reactions from experiences that, while challenging during the session, yield long-term psychological well-being.
Complementary psychometric batteries include the 5-Dimensional Altered States of Consciousness Rating Scale (5D-ASC) developed by Adolf Dittrich, specifically its “Dread of Ego Dissolution” (AIA) dimension, which measures anxious ego disintegration, loss of autonomy, and thought disorder. In addition, the States of Consciousness Questionnaire (SOCQ) and the Mystical Experience Questionnaire (MEQ30) include challenge dimensions to evaluate the dialectical balance between mystical and distressing states during high-dose psychedelic administration.
10. Applications & Practical Significance
Understanding and managing the bad trip is of paramount importance across emergency medicine, psychiatric practice, and community harm reduction. The clinical protocols established during the resurgence of psychedelic-assisted therapy have fundamentally reshaped modern management strategies.
In clinical trials and emerging psychiatric therapy utilizing psilocybin, LSD, or MDMA, adverse psychological reactions are managed primarily through proactive non-pharmacological scaffolding. This methodology rests on three pillars:
- Extensive Preparation: Therapists conduct hours of pre-session preparation, establishing strong therapeutic alliance, explaining the physiological and psychological actions of the drug, and explicitly instructing the patient on surrender techniques (e.g., “in and through”) when encountering terrifying visions or somatic sensations.
- Carefully Engineered Setting: Sessions take place in quiet, aesthetic, living-room-like environments with controlled lighting, curated music, and constant supervision by trained co-therapists, minimizing chaotic external stimuli that trigger paranoia.
- Verbal De-escalation Over Pharmacological Restraint: If acute terror manifests, therapists utilize verbal reassurance, calming vocal cadence, touch support, and breathing exercises. Second-generation antipsychotics or benzodiazepines (such as diazepam or lorazepam) are maintained as rescue medications strictly as a last resort, as pharmacological termination can interrupt therapeutic catharsis and leave traumatic emotional fragments unresolved.
In public, recreational, and festival environments, grassroots organizations such as the Multidisciplinary Association for Psychedelic Studies (MAPS) Zendo Project have established the standard of care for psychedelic harm reduction. The core principles—Create a safe space; Sitting, not guiding; Talk through, not down; and Difficult is not the same as bad—divert thousands of distressed individuals from unnecessary, costly, and traumatizing emergency room visits and police interactions.
11. Research & Empirical Evidence
Contemporary empirical research has debunked several enduring myths surrounding bad trips while delineating their genuine clinical risks. In a landmark survey study conducted by Roland Griffiths and colleagues at Johns Hopkins University (2016), researchers surveyed nearly 2,000 individuals who had experienced a profound challenging experience with psilocybin. Remarkably, 84% of respondents reported benefiting from the difficult episode, with 34% declaring it among the top five most personally meaningful experiences of their entire lives. However, the study also demonstrated tangible dangers: 10.7% put themselves or others at risk of physical harm, 2.6% behaved aggressively or violently, and a small minority required professional psychiatric assistance in the weeks following the event.
Neuroimaging investigations led by Robin Carhart-Harris, Katrin Preller, and Franz Vollenweider have clarified the neural correlates of anxious ego dissolution. Functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) studies demonstrate that during severe anxious ego dissolution, the decoupling of the frontoparietal control network and the default mode network occurs alongside hyper-activation of the amygdala and disruption of thalamocortical sensory gating. When individuals feel unsupported, the amygdala responds to sensory overflow with unconstrained fear signals.
Longitudinal studies on clinical patient populations undergoing psilocybin therapy for treatment-resistant depression or end-of-life existential distress show that moderate CEQ scores do not negatively predict therapeutic outcomes. In fact, multiple studies indicate that experiencing and resolving acute psychological challenge during a psychedelic session frequently correlates with greater long-term decreases in depressive symptoms, provided that competent post-session integration therapy is available to contextualize the experience.
12. Cultural & Cross-Cultural Considerations
The phenomenological occurrence and social framing of adverse hallucinogenic episodes vary markedly across cultural contexts. In Western industrial societies, where psychedelics are frequently consumed illicitly, recreationally, and without formal ritual containment, the absence of clear metaphysical frameworks significantly heightens the likelihood of acute panic. Western individualism fosters an ego identity characterized by tight self-control and autonomy; hence, the involuntary dissolution of this ego identity is readily pathologized as organic madness or brain destruction.
In contrast, indigenous societies possessing continuous lineages of entheogen use embed altered states within robust cultural, cosmological, and communal scaffolding. Among the Mazatec of Mexico, who utilize psilocybin-containing mushrooms (veladas), or indigenous Amazonian groups who drink ayahuasca, terrifying encounters with predatory spirits, ancestral judgment, or intense physical purging (la purga) are understood as standard, necessary phases of healing and energetic balance. The curandero or shamans act as steady spiritual navigators, containing the crisis through ritualized songs, sacred plants, and clear cosmological explanations. Consequently, what a Western user might report as an aberrant, traumatizing bad trip is culturally recognized in traditional settings as an initiatory death or profound somatic cleanse.
Cross-cultural psychiatry emphasizes that the semiotics of the bad trip are heavily populated by culture-bound idioms of distress. While a secular Western user may experience paranoia centered around law enforcement, psychiatric wards, or biological death, users from deeply religious or traditional backgrounds are significantly more likely to experience visions of demonic possession, cosmic damnation, or ancestral vengeance.
13. Criticisms, Debates & Limitations
The discourse surrounding bad trips remains a terrain of rigorous academic and clinical debate. One primary controversy revolves around the terminological push to rebrand all bad trips as challenging experiences. While advocates argue that this reframing destigmatizes psychological distress and highlights therapeutic potential, critics in emergency medicine and clinical psychiatry caution that it risks romanticizing genuine psychiatric emergencies. In cases involving reckless polydrug consumption, extremely high doses, or underlying psychotic vulnerability, adverse reactions can result in severe physical trauma, accidental suicide, acute violent agitation, or prolonged psychiatric decompensation that cannot be hand-waved away as mere personal growth.
Another major debate centers on the causal relationship between bad trips and the triggering of long-term psychiatric illness. Epidemiological studies by Teri Krebs and Pål-Ørjan Johansen utilizing United States national health survey data found no significant association between lifetime psychedelic use and increased rates of mental health disorders. Nevertheless, clinical consensus acknowledges that in individuals with a strong personal or family predisposition to schizophrenia, bipolar I disorder, or other primary psychotic disorders, a severe, destabilizing psychedelic crisis can precipitate the early onset of a chronic psychotic episode.
Furthermore, persistent controversies surround the etiology and prevalence of Hallucinogen Persisting Perception Disorder (HPPD). While HPPD involves enduring perceptual disturbances (such as visual snow, halos, and geometric patterns) post-sobering, its co-occurrence with chronic somatic anxiety and depersonalization-derealization disorder is significantly higher in individuals whose psychedelic episodes involved acute panic and traumatic terror, highlighting the complex boundary between neurosensory disruption and post-traumatic stress.
14. Related Terms & Distinctions
To avoid conceptual conflation, the bad trip must be differentiated from several related psychological, medical, and pharmacological phenomena:
- Challenging Psychedelic Experience: The preferred academic and clinical umbrella term. While a bad trip colloquially implies an entirely negative, disastrous failure, a challenging experience encompasses emotionally arduous, painful, or terrifying phases that are safely navigated and ultimately yield positive psychological insight and catharsis.
- Hallucinogen-Induced Psychotic Disorder: A formal diagnostic category (DSM-5-TR / ICD-11) reserved for persistent psychotic symptoms (delusions, hallucinations, gross thought disorder) that endure well beyond the expected pharmacological duration of the psychoactive drug, indicating unmasked or de novo psychiatric pathology rather than acute intoxication distress.
- Toxic Psychosis / Delirium: An organic brain syndrome typically characterized by global disorientation, fluctuating consciousness, motor ataxia, and amnesia, commonly induced by anticholinergic agents (such as datura or scopolamine) or toxic overdoses of synthetic stimulants, contrasting with the intact sensorium typically maintained during classical psychedelic use.
- Panic Disorder with Agoraphobia: An idiopathic, recurrent anxiety disorder occurring in the absence of exogenous substances. While an acute bad trip frequently features severe panic attacks, it is substance-induced and self-limiting in nature.
- Ego Death (Ego Dissolution): A complete subjective loss of self-identity and subject-object duality. When accompanied by psychological acceptance, it is experienced as ecstatic unity; when accompanied by resistance and fear, it manifests as the central crisis of a bad trip.
- Post-Psychedelic Depersonalization/Derealization: A persistent dissociative reaction triggered in the weeks or months following a traumatic, terrifying psychedelic episode, functioning as a psychological defense against unresolved acute panic.
15. Summary / Key Takeaways
The phenomenon historically known as a bad trip represents an acute, temporary adverse psychological crisis occurring during hallucinogen intoxication. Far from being a random or purely pharmacological side effect, it is an emergent property shaped dynamically by drug pharmacology, dosage, internal psychological set, and external environmental setting. Its manifestations span panic, paranoia, terror of ego dissolution, somatic distress, and cognitive loops.
Modern psychedelic science has fundamentally reframed these episodes from unmitigated psychiatric disasters into complex psychological challenges that, within structured therapeutic environments, can catalyze profound emotional breakthroughs. However, in uncontrolled, recreational settings without psychological safety or containment, acute distress carries tangible risks of behavioral misadventure and psychological trauma. Effective management prioritizes empathetic, non-judgmental human presence, verbal de-escalation, and structured therapeutic integration, ensuring that the human psyche is supported when navigating the turbulent depths of expanded consciousness.
References
- Carhart-Harris, R. L., & Friston, K. J. (2019). REBUS and the anarchic brain: Toward a unified model of the brain action of psychedelics. Pharmacological Reviews, 71(3), 316–344. https://doi.org/10.1124/pr.118.017160
- Griffiths, R. R., Richards, W. A., McCann, U., & Jesse, R. (2006). Psilocybin can occasion mystical-type experiences having substantial and sustained personal meaning and spiritual significance. Psychopharmacology, 187(3), 268–283. https://doi.org/10.1007/s00213-006-0457-5
- Grof, S. (2008). LSD psychotherapy: The healing potential of psychedelic medicine. MAPS. https://maps.org/product/lsd-psychotherapy/
- Johnson, M. W., Richards, W. A., & Griffiths, R. R. (2008). Human hallucinogen research: Guidelines for safety. Journal of Psychopharmacology, 22(6), 603–620. https://doi.org/10.1177/0269881108093587
- MacLean, K. A., Leoutsakos, J. M., Johnson, M. W., & Griffiths, R. R. (2016). Factor analysis of the Challenging Experience Questionnaire (CEQ): A comprehensive measure of challenging experiences with psilocybin mushrooms. Journal of Psychopharmacology, 30(7), 664–678. https://doi.org/10.1177/0269881116642980