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    Hallucinations and delusions

    幻觉与妄想

    Concept
    Also called
    hallucination, delusion, hearing voices, psychotic experiences, psychotic-like experiences, hypnagogic hallucinations

    What are hallucinations and delusions?

    A hallucination is a perception, in any sense, without the matching external stimulus; a delusion is a belief that is clearly untrue or not shared by others, held with conviction and barely shaken by contrary evidence.[1] Both are symptoms, not diagnoses, and occur in many mental and physical conditions.[1][2]

    Can happen without a mental disorder

    Causes to check

    Schematic, not a self-test. Bars drawn to scale.

    Select a box for details.
    Schematic, not a self-test. At the top, the two symptoms and the continuum ICD-11 describes; in the middle, experiences that can occur without a mental disorder, with bars drawn to scale from surveys in 18 countries, beside causes to check; at the bottom, when to get help. Select a part for details. Select a part for details
    Schematic, not a self-test. At the top, the two symptoms and the continuum ICD-11 describes; in the middle, experiences that can occur without a mental disorder, with bars drawn to scale from surveys in 18 countries, beside causes to check; at the bottom, when to get help. Select a part for details. Save as image (PNG)

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    Key points

    • They are not unique to schizophrenia: bipolar disorder, severe depression, dementia, Parkinson’s disease, alcohol, drugs, some medicines, high fever, infection and delirium can all cause them.[1][2]
    • ICD-11 places experiences of losing or distorting reality on a continuum across the population; only when frequent and intense enough to depart from cultural norms might they mean a psychotic disorder.[1]
    • Across 18 countries, 5.8% of 31,261 adults had ever had a hallucinatory or delusional experience (hallucinatory 5.2%, delusional 1.3%); nearly a third of them had just one.[3]
    • Brief hallucinations while falling asleep or waking can be temporary.[2] Some 30–60% of bereaved people sense, hear or see the person who died, and most find it comforting.[4]

    An example

    After three short nights finishing a paper, Lin lies down at dawn and, as she drifts off, clearly hears someone call her name. No one is there. Once she catches up on sleep, it never recurs. Hallucinations with severe sleep loss or at the edges of sleep can be temporary; repeated ones while awake call for a doctor.[2]

    Misreadings and limits

    Hearing what others cannot does not mean schizophrenia; people in the general population report it too.[1][3] Nor should it be shrugged off: this page is not for self-diagnosis. New hallucinations need prompt medical advice, especially with fever or confusion. Fast-worsening symptoms, or voices telling you to harm yourself or others, need emergency care now.[2]

    If you need help now

    If you’re struggling to cope or having thoughts of harming yourself:

    If you’re in immediate danger, call your local emergency number.

    Psyfield is not a crisis service. Numbers checked October 2026.

    Sources

    1. 1 World Health Organization (2025). MB26.0 Delusion; MB27.2 Hallucinations; 7B02.1 Sleep-related hallucinations; Schizophrenia or other primary psychotic disorders. ICD-11 for mortality and morbidity statistics (2025-01 release). View source
    2. 2 NHS (2025). Hallucinations and hearing voices. NHS website (last reviewed 28 July 2025). View source
    3. 3 McGrath, J. J., Saha, S., Al-Hamzawi, A., Alonso, J., Bromet, E. J., Bruffaerts, R., Caldas-de-Almeida, J. M., Chiu, W. T., de Jonge, P., Fayyad, J., Florescu, S., Gureje, O., Haro, J. M., Hu, C., Kovess-Masfety, V., Lepine, J. P., Lim, C. C. W., Medina Mora, M. E., Navarro-Mateu, F., … Kessler, R. C. (2015). Psychotic experiences in the general population: A cross-national analysis based on 31,261 respondents from 18 countries. JAMA Psychiatry, 72(7), 697–705. doi:10.1001/jamapsychiatry.2015.0575
    4. 4 Sabucedo, P., Evans, C., & Hayes, J. (2023). Perceiving those who are gone: Cultural research on post-bereavement perception or hallucination of the deceased. Transcultural Psychiatry, 60(6), 879–890. doi:10.1177/1363461520962887

    Last checked against sources: October 28, 2026