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 Bulletin
June 8, 2016
Ben Alderson-Day, Kelly Diederen, Charles Fernyhough et al.
134 citations
Resting-state brain networks may help explain hallucinations across different sensory modalities and populations. This report from the International Consortium on Hallucination Research reviews evidence linking resting-state alterations to auditory hallucinations, finding connectivity differences in left-hemisphere auditory and language regions, plus atypical interactions of the default mode network with networks for cognitive control and salience. Similar patterns appear in visual hallucinations, suggesting both domain-general and modality-specific network changes. However, high methodological heterogeneity across studies limits direct comparisons. The authors offer recommendations for future research on resting-state connectivity and hallucinations.
Schizophrenia Bulletin
August 5, 2020
Pantelis Leptourgos, Martin Fortier-Davy, Robin Carhart-Harris et al.
88 citations
A multidisciplinary working group reviewed evidence on the similarities and differences between hallucinations induced by psychedelics and those occurring in schizophrenia-spectrum disorders, examining data from pharmacology, brain imaging, phenomenology, and anthropology. The authors highlight both shared features and distinct characteristics across these scales, and attempt to integrate findings using computational approaches. They conclude with recommendations for future research, emphasizing the need for further study to clarify the relationship between these types of hallucinations.
Schizophrenia Bulletin
August 8, 2018
T. M. Luhrmann, Ben Alderson-Day, Vaughan Bell et al.
74 citations
Trauma can contribute to voice-hearing but is not necessary for it. This article uses ethnographic and other data to show multiple pathways to voice-hearing in both clinical and nonclinical populations, excluding known causes like drugs or epilepsy. Trauma sometimes plays a major role, sometimes a minor role, and sometimes no role at all. Distinct phenomenological patterns in voice-hearing may reflect different salience of trauma for those who hear voices.
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.
BJPsych Open
July 25, 2022
Deborah Wearne, Jeremiah Ayalde, Guy Curtis et al.
10 citations
Visual hallucinations in people with PTSD can be indistinguishable from those in schizophrenia. A study comparing three groups who hear voices—schizophrenia without trauma history (19 participants), PTSD with dissociation (17 participants), and comorbid schizophrenia and PTSD (20 participants)—found remarkable similarity in visual experiences, including rates of complex visual hallucinations, across all groups. No significant differences emerged in the severity or components of distress surrounding these experiences. Dissociation predicted visual hallucination severity only for the comorbid group, not for PTSD or schizophrenia alone. Multimodal hallucinations were frequent in both schizophrenia and PTSD. The authors suggest a model for visual hallucinations in PTSD following two separate neurobiological pathways based on distinct trauma responses.
Schizophrenia Bulletin
April 17, 2025
Nathan H. Heller, Frederick S. Barrett, Tobias Buchborn et al.
3 citations
Visual hallucinations in Lewy body diseases (Parkinson's disease and dementia with Lewy bodies) and those induced by serotonergic psychedelics (psilocybin, mescaline) share overlapping phenomenology and neural mechanisms, despite different underlying causes. Both conditions produce visual aberrations from minor distortions to complex hallucinations, including illusory motion and entity encounters. Neuroimaging shows a common pattern of overactive associative cortex and underactive sensory cortex. Serotonin 2A receptor modulation is involved in both: psychedelics act through 5-HT2A and 5-HT1A receptors, while in Lewy body diseases, 5-HT2A receptor upregulation correlates with increased hallucinations, and blocking it with pimavanserin reduces them. Shared cortical signatures include reduced visual evoked responses and shifts toward visual excitation.
Psychiatry Research
January 1, 2023
Flavie Waters
1 citation
Hallucinations are among the least understood human experiences, recognized across cultures and in both mental illness and those not mentally unwell. Early research on hallucinogens like LSD was criticized and withdrawn, but its revival offers new opportunities to examine the mechanism of hallucinating. Studying psychedelic compounds in controlled settings with mentally healthy individuals may reveal temporal shifts in perceptual awareness, decode what influences contents, affect, meaning, and appraisals of hallucinations, and guide novel psychotherapy and drug therapy.
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.