Frontiers in Psychiatry
July 10, 2018
Flavie Waters, Vivian Chiu, Amanda Atkinson et al.
163 citations
Going without sleep for long periods reliably produces perceptual distortions, hallucinations, and other psychotic symptoms that worsen over time. A systematic review of historical studies covering 760 participants who were kept awake for 24 hours to 11 nights found that visual distortions and illusions were the most common effects, appearing in 90% of studies, followed by somatosensory changes (52%) and auditory hallucinations (33%). Symptoms emerged rapidly: perceptual distortions, anxiety, irritability, depersonalization, and temporal disorientation began within 24-48 hours; complex hallucinations and disordered thinking after 48-90 hours; and delusions after 72 hours, at which point the condition resembled acute psychosis or toxic delirium. A period of normal sleep resolved symptoms in most but not all cases.
Schizophrenia
April 23, 2022
Mascha M.J. Linszen, Janna De Boer, Maya Schutte et al.
55 citations
Hallucinations occur in 6-15% of the general population, but their detailed characteristics are poorly understood. In a large online survey of 10,448 participants aged 14-88, auditory hallucinations were most common in the past month (29.5%), followed by visual (21.5%), tactile (19.9%), and olfactory (17.3%); nearly half (47.6%) experienced hallucinations in two or more senses. Many participants rated their hallucinations as severe due to negative content (16.0-31.6%), distress (10.5-16.8%), or dysfunction (12.7-17.3%). Decreased insight occurred in 10.2-11.4%, hypnagogia in 9.0-10.6%, and bereavement hallucinations in 2.8%. Delusions were rare (7.0%) but significantly associated with recent hallucinations. The findings indicate a wide variety of hallucination phenomenology in the general population and support a phenomenological continuum.
Frontiers in Neuroscience
August 11, 2021
Pieter J. Vis, Anneke E. Goudriaan, Bastiaan C. Ter Meulen et al.
40 citations
Hallucinogen-persisting perception disorder (HPPD) involves perceptual symptoms and flashbacks after psychedelic use, but its phenomenology is poorly understood. A systematic review of 66 case reports and series covering 97 people identified 64 unique symptoms. Of these, 76% were characteristic of Alice in Wonderland syndrome, over 50% were non-visual, and 38% were not clearly linked to prior intoxication, contrasting with DSM-5 criteria. Fewer than half of patients had a protracted course over a year, and a third achieved remission. Co-occurring depression with or without anxiety was associated with longer symptom persistence and more negative treatment outcomes. HPPD involves changes in the content of consciousness and an attentional shift from external to internal phenomena, rather than the altered states seen in acute intoxication. The authors recommend expanding diagnostic criteria.
Philosophical Transactions of the Royal Society B Biological Sciences
December 13, 2020
Flavie Waters, Joseph M Barnby, Jan Dirk Blom
26 citations
Hallucinations, mental imagery, and dreams share a common feature: they are perceptions that occur without matching external stimulation. Historically, medical and psychological sciences have studied these experiences separately, but this review examines their similarities and differences in phenomenology and brain function to unite them within a single framework. Using Edmund Parish's historical work alongside current cognitive, clinical, and computational research, the authors consider how different perspectives can be reconciled to generate new hypotheses for future investigation.
Harv Rev Psychiatry
September 9, 2025
Arjen Neven, Jan Dirk Blom
3 citations
Hallucinogen persisting perception disorder (HPPD) involves lingering or recurring perceptual phenomena after substance use, which can be mild or severely burdensome. A systematic review of 31 medication studies covering 87 participants found that clonidine, clonazepam, and levetiracetam produced substantial symptom reduction in three observational studies. Among those receiving benzodiazepines, antiepileptics, antidepressants, or alpha agonists, 28% achieved full recovery and 61% partial recovery within a year. Benzodiazepines were ineffective when HPPD was triggered by lysergic acid diethylamide, and risperidone aggravated symptoms. The authors suggest these medications can treat HPPD effectively but call for randomized controlled trials and epidemiological studies.
Frontiers in Psychology
March 7, 2024
Fatih Incekara, Jan Dirk Blom
2 citations
Based on a phenomenological analysis of Carl Jung's self-reports in a seven-volume journal and other writings, several types of anomalous perceptual experiences are identified: hypnagogic-hypnopompic experiences, hyperphantasia, hallucinations, personifications, and sensed presence. These experiences were not indicative of a psychotic disorder but stemmed from extremely vivid mental imagery, or hyperphantasia, a condition not conceptualized during Jung's time. Jung may have foreshadowed research on reality equivalence, where inner mental reality substitutes for external perception. Future research should investigate hyperphantasia's role in psychotic experiences, but Jung himself managed to contextualize and find meaning in his experiences, sharing them with others.
Sleep medicine clinics
March 1, 2024
Flavie Waters, Ivan Ling, Somayyeh Azimi et al.
Sleep-related hallucinations are now classified separately from terrifying hypnagogic hallucinations. Hypnagogic and hypnopompic hallucinations occurring without other symptoms and within normal sleep are likely non-pathological. In contrast, complex nocturnal visual hallucinations may indicate psychopathology arising from different combinations of causes. This newer concept requires further research to determine whether it shares mechanisms with hypnagogic and hypnopompic hallucinations.
Frontiers in Psychiatry
January 1, 2022
Marc L Molendijk, Ouarda Bouachmir, Harriët Montagne et al.
The incubus phenomenon—a terrifying sleep-related experience of feeling a person or entity pressing on one's chest during sleep paralysis—was studied in 749 people (606 university students and 143 patients with schizophrenia spectrum disorders). Lifetime prevalence was 0.12 for students and 0.09 for patients, rates that did not differ statistically. These figures are substantially lower than the 0.41 reported in an earlier meta-analysis, which the authors suggest may reflect overgeneralization in prior studies. The phenomenon was more common among people with non-Western European backgrounds, possibly because it remains part of cultural and religious heritage in many non-Western countries. Among students, risk factors included psychotropic medication use and lifetime anxiety, eating, or sleeping disorders. No associations with age or gender were found.
Transcultural Psychiatry
December 1, 2015
Jan Dirk Blom, Igmar T Poulina, Trevor L Van Gellecum et al.
Brua, an Afro-Caribbean religion and healing tradition from the southern former Netherlands Antilles, shapes how individuals experience and express disorders that Western psychiatry considers mental illness. A systematic review of 35 texts—including three peer-reviewed papers and eight theses—found Brua to be a holistic patchwork of creolized beliefs and practices seen as both cause and remedy for ailments. Tension between Brua and Western psychiatric practice is significant, but adherence does not seem to cause much patient delay in help-seeking. However, belief in Brua as a source of complaints and patients' use of practices including hallucinogens may affect diagnosis and treatment of mental disorders.
Harvard Review of Psychiatry
Jan Dirk Blom, Rosemarij J B Van Veen, Emma H C Van Rooijen et al.
Sexual hallucinations—often distressing genital, orgasmic, or other sensory experiences—are more common in women than men (sex ratio 1.4:1) and most prevalent in schizophrenia spectrum disorders, with rates from 1.4% in recently admitted patients to 44% in chronically hospitalized patients. Other causes include epilepsy, sleep paralysis (incubus phenomenon), narcolepsy, and sedative use. In anesthesia, some reported sexual sensations are not hallucinations but real medicolegal events. No evidence-based treatment protocols exist; guidelines focus on the underlying condition. More research is needed on substance abuse, PTSD, and borderline personality disorder, and clinician awareness should improve.