Hallucination
Hallucination | |
---|---|
My eyes at the moment of the apparitions by August Natterer, a German artist who created many drawings of his hallucinations | |
Specialty | Psychiatry |
Causes | Hypnagogia, Peduncular hallucinosis, Delirium tremens, Parkinson's disease, Lewy body dementia, Charles Bonnet syndrome, Hallucinogen, Sensory deprivation, Anomalous experiences, Non-celiac gluten sensitivity[1] |
Treatment | Cognitive behavioral therapy[2] and metacognitive training[3] |
Medication | Antipsychotic, AAP |
A hallucination is a
Hallucinations can occur in any
A mild form of hallucination is known as a disturbance, and can occur in most of the senses above. These may be things like seeing movement in peripheral vision, or hearing faint noises or voices. Auditory hallucinations are very common in schizophrenia. They may be benevolent (telling the subject good things about themselves) or malicious, cursing the subject. 55% of auditory hallucinations are malicious in content,[8] for example, people talking about the subject, not speaking to them directly. Like auditory hallucinations, the source of the visual counterpart can also be behind the subject. This can produce a feeling of being looked or stared at, usually with malicious intent.[citation needed] Frequently, auditory hallucinations and their visual counterpart are experienced by the subject together.[9]
The word "hallucination" itself was introduced into the English language by the 17th-century physician Sir Thomas Browne in 1646 from the derivation of the Latin word alucinari meaning to wander in the mind. For Browne, hallucination means a sort of vision that is "depraved and receive[s] its objects erroneously".[11]
Classification
Hallucinations may be manifested in a variety of forms.[12] Various forms of hallucinations affect different senses, sometimes occurring simultaneously, creating multiple sensory hallucinations for those experiencing them.[6]
Auditory
Auditory hallucinations (also known as paracusia)[13] are the perception of sound without outside stimulus. Auditory hallucinations can be divided into elementary and complex, along with verbal and nonverbal. These hallucinations are the most common type of hallucination, with auditory verbal hallucinations being more common than nonverbal.[14][15] Elementary hallucinations are the perception of sounds such as hissing, whistling, an extended tone, and more.[16] In many cases, tinnitus is an elementary auditory hallucination.[15] However, some people who experience certain types of tinnitus, especially pulsatile tinnitus, are actually hearing the blood rushing through vessels near the ear. Because the auditory stimulus is present in this situation, it does not qualify it as a hallucination.[citation needed]
Complex hallucinations are those of voices, music,[15] or other sounds that may or may not be clear, may or may not be familiar, and may be friendly, aggressive, or among other possibilities. A hallucination of a single individual person of one or more talking voices is particularly associated with psychotic disorders such as schizophrenia, and hold special significance in diagnosing these conditions.[citation needed]
In schizophrenia, voices are normally perceived coming from outside the person, but in dissociative disorders they are perceived as originating from within the person, commenting in their head instead of behind their back. Differential diagnosis between schizophrenia and
Musical hallucinations are also relatively common in terms of complex auditory hallucinations and may be the result of a wide range of causes ranging from hearing-loss (such as in
The Hearing Voices Movement is a support and advocacy group for people who hallucinate voices, but do not otherwise show signs of mental illness or impairment.[22]
High caffeine consumption has been linked to an increase in likelihood of one experiencing auditory hallucinations.[23] A study conducted by the La Trobe University School of Psychological Sciences revealed that as few as five cups of coffee a day (approximately 500 mg of caffeine) could trigger the phenomenon.[24]
Visual
A visual hallucination is "the perception of an external visual stimulus where none exists".[25] A separate but related phenomenon is a visual illusion, which is a distortion of a real external stimulus. Visual hallucinations are classified as simple or complex:
- Simple visual hallucinations (SVH) are also referred to as non-formed visual hallucinations and elementary visual hallucinations. These terms refer to lights, colors, geometric shapes, and indiscrete objects. These can be further subdivided into phosphenes which are SVH without structure, and photopsias which are SVH with geometric structures.
- Complex visual hallucinations (CVH) are also referred to as formed visual hallucinations. CVHs are clear, lifelike images or scenes such as people, animals, objects, places, etc.
For example, one may report hallucinating a giraffe. A simple visual hallucination is an amorphous figure that may have a similar shape or color to a giraffe (looks like a giraffe), while a complex visual hallucination is a discrete, lifelike image that is, unmistakably, a giraffe.
Command
Command hallucinations are hallucinations in the form of commands; they appear to be from an external source, or can appear coming from the subject's head.[26] The contents of the hallucinations can range from the innocuous to commands to cause harm to the self or others.[26] Command hallucinations are often associated with schizophrenia. People experiencing command hallucinations may or may not comply with the hallucinated commands, depending on the circumstances. Compliance is more common for non-violent commands.[27]
Command hallucinations are sometimes used to defend a crime that has been committed, often homicides.[28] In essence, it is a voice that one hears and it tells the listener what to do. Sometimes the commands are quite benign directives such as "Stand up" or "Shut the door."[29] Whether it is a command for something simple or something that is a threat, it is still considered a "command hallucination." Some helpful questions that can assist one in determining if they may have this includes: "What are the voices telling you to do?", "When did your voices first start telling you to do things?", "Do you recognize the person who is telling you to harm yourself (or others)?", "Do you think you can resist doing what the voices are telling you to do?"[29]
Olfactory
Phantosmia (olfactory hallucinations), smelling an odor that is not actually there,
Tactile
Tactile hallucinations are the illusion of tactile sensory input, simulating various types of pressure to the skin or other organs. One subtype of tactile hallucination, formication, is the sensation of insects crawling underneath the skin and is frequently associated with prolonged cocaine use.[33] However, formication may also be the result of normal hormonal changes such as menopause, or disorders such as peripheral neuropathy, high fevers, Lyme disease, skin cancer, and more.[33]
Gustatory
This type of hallucination is the perception of taste without a stimulus. These hallucinations, which are typically strange or unpleasant, are relatively common among individuals who have certain types of
Sexual
Sexual hallucinations are the perception of erogenous or orgasmic stimuli. They may be unimodal or multimodal in nature and frequently involve sensation in the genital region, though it is not exclusive. [36]Frequent examples of sexual hallucinations include the sensation of being penetrated, experiencing orgasm, feeling as if one is being touched in an erogenous zone, sensing stimulation in the genitals, feeling the fondling of one's breasts or buttocks and tastes or smells related to sexual activity.[37] Visualizations of sexual content and auditory voices making sexually explicit remarks may sometimes be included in this classification. While it features components of other classifications, sexual hallucinations are distinct due to the orgasmic component and unique presentation. [38]
The regions of the brain responsible differ by the subsection of sexual hallucination. In orgasmic auras, the mesial temporal lobe, right amygdala and hippocampus are involved. [39][40]In males, genital specific sensations are related to the postcentral gyrus and arousal and ejaculation are linked to stimulation in the posterior frontal lobe.[41][42] In females, however, the hippocampus and amygdala are connected.[42][43] Limited studies have been done to understand the mechanism of action behind sexual hallucinations in epilepsy, substance use, and post-traumatic stress disorder etiologies. [38]
Somatic
Somatic hallucinations refer to an interoceptive sensory experience in the absence of stimulus. Somatic hallucinations can be broken down into further subcategories: general, algesic, kinesthetic, and cenesthopathic.[36][38]
- Cenesthopathic- Effecting the sensory modality, cenesthopathic hallucinations are a pathological alteration in the sense of bodily existence, caused by aberrant bodily sensations Most often, cenesthopathic hallucinations will refer to sensation in the visceral organs. Therefore, it is also known as visceral hallucinations.[44] [38]Manifestations are often subjective, hard to describe and unique to the sufferer. Common manifestations include pressure, burning, tickling, or tightening in various body systems. [45]While these hallucinations can be experienced by a variety of psychiatric and neurological disorder, cenesthopathic schizophrenia is recognized by the ICD as a subtype of schizophrenia marked by primarily cenesthopathic hallucinations and other body image aberrations.[46] [38]
- Kinesthetic- Kinesthetic hallucinations, effecting the sensory modality of the same name, are the sensation of movement of the limbs or other body parts without actual movement. [47][38][45][44]
- Algesic- Algesic hallucinations, effecting the algesic sensory modality, refers to a perceived perception of pain.[38][45][44]
- General- General somatic hallucination refers to somatic hallucinations not otherwise categorized by the above subsections. Common examples include when an individual feels that their body is being mutilated, i.e. twisted, torn, or disemboweled. Other reported cases are invasion by animals in the person's internal organs, such as snakes in the stomach or frogs in the rectum. The general feeling that one's flesh is decomposing is also classified under this type of this hallucination.[38]
Multimodal
A hallucination involving sensory modalities is called multimodal, analogous to unimodal hallucinations which have only one sensory modality. The multiple sensory modalities can occur at the same time (simultaneously) or with a delay (serial), be related or unrelated to each other, and be consistent with reality (congruent) or not (incongruent).[6][7] For example, a person talking in a hallucination would be congruent with reality, but a cat talking would not be.
Multimodal hallucinations are correlated to poorer mental health outcomes, and are often experienced as feeling more real.[6]
Cause
Hallucinations can be caused by a number of factors.[48]
Hypnagogic hallucination
These hallucinations occur just before falling asleep and affect a high proportion of the population: in one survey 37% of the respondents experienced them twice a week.[49] The hallucinations can last from seconds to minutes; all the while, the subject usually remains aware of the true nature of the images. These may be associated with narcolepsy. Hypnagogic hallucinations are sometimes associated with brainstem abnormalities, but this is rare.[50]
Peduncular hallucinosis
Peduncular means pertaining to the
Delirium tremens
One of the more enigmatic forms of visual hallucination is the highly variable, possibly polymodal
Parkinson's disease and Lewy body dementia
Migraine coma
This type of hallucination is usually experienced during the recovery from a comatose state. The migraine coma can last for up to two days, and a state of depression is sometimes comorbid. The hallucinations occur during states of full consciousness, and insight into the hallucinatory nature of the images is preserved. It has been noted that ataxic lesions accompany the migraine coma.[50]
Charles Bonnet syndrome
Focal epilepsy
Visual hallucinations due to focal seizures differ depending on the region of the brain where the seizure occurs. For example, visual hallucinations during occipital lobe seizures are typically visions of brightly colored, geometric shapes that may move across the visual field, multiply, or form concentric rings and generally persist from a few seconds to a few minutes. They are usually unilateral and localized to one part of the visual field on the contralateral side of the seizure focus, typically the temporal field. However, unilateral visions moving horizontally across the visual field begin on the contralateral side and move toward the ipsilateral side.[34][55]
Distortions in visual perception during a temporal lobe seizure may include size distortion (micropsia or macropsia), distorted perception of movement (where moving objects may appear to be moving very slowly or to be perfectly still), a sense that surfaces such as ceilings and even entire horizons are moving farther away in a fashion similar to the dolly zoom effect, and other illusions.[56] Even when consciousness is impaired, insight into the hallucination or illusion is typically preserved.[citation needed]
Drug-induced hallucination
Drug-induced hallucinations are caused by
Hallucinations,
Sensory deprivation hallucination
Hallucinations can be caused by sensory deprivation when it occurs for prolonged periods of time, and almost always occurs in the modality being deprived (visual for blindfolded/darkness, auditory for muffled conditions, etc.) [61]
Experimentally-induced hallucinations
Anomalous experiences, such as so-called benign hallucinations, may occur in a person in a state of good mental and physical health, even in the apparent absence of a transient trigger factor such as
The evidence for this statement has been accumulating for more than a century. Studies of benign hallucinatory experiences go back to 1886 and the early work of the Society for Psychical Research,[62][63] which suggested approximately 10% of the population had experienced at least one hallucinatory episode in the course of their life. More recent studies have validated these findings; the precise incidence found varies with the nature of the episode and the criteria of "hallucination" adopted, but the basic finding is now well-supported.[64]
Non-celiac gluten sensitivity
There is tentative evidence of a relationship with non-celiac gluten sensitivity, the so-called "gluten psychosis".[65]
Pathophysiology
Dopaminergic and serotonergic hallucinations
It has been reported that in serotonergic hallucinations, the person maintains an awareness that they are hallucinating, unlike dopaminergic hallucinations.[10]
Neuroanatomy
Hallucinations are associated with structural and functional abnormalities in primary and secondary sensory cortices. Reduced grey matter in regions of the
One proposed model of hallucinations posits that over-activity in sensory regions, which is normally attributed to internal sources via feedforward networks to the inferior frontal gyrus, is interpreted as originating externally due to abnormal connectivity or functionality of the feedforward network.[66] This is supported by cognitive studies of those with hallucinations, who have demonstrated abnormal attribution of self generated stimuli.[68]
Disruptions in thalamocortical circuitry may underlie the observed top down and bottom up dysfunction.
Abnormal assignment of salience to stimuli may be one mechanism of hallucinations. Dysfunctional dopamine signaling may lead to abnormal top down regulation of sensory processing, allowing expectations to distort sensory input.[71]
Treatments
There are few treatments for many types of hallucinations. However, for those hallucinations caused by mental disease, a psychologist or psychiatrist should be consulted, and treatment will be based on the observations of those doctors. Antipsychotic and atypical antipsychotic medication may also be utilized to treat the illness if the symptoms are severe and cause significant distress.[72] For other causes of hallucinations there is no factual evidence to support any one treatment is scientifically tested and proven. However, abstaining from hallucinogenic drugs, stimulant drugs, managing stress levels, living healthily, and getting plenty of sleep can help reduce the prevalence of hallucinations. In all cases of hallucinations, medical attention should be sought out and informed of one's specific symptoms. Meta-analyses show that cognitive behavioral therapy[73] and metacognitive training[74] can also reduce the severity of hallucinations. Furthermore, there are recovery movements all around the world that advocate for individuals with schizophrenia or voice-hearers (individuals that hear voices). The Hearing Voices Movement,[75] starting in Europe, is a great example of utilizing the knowledge and experience of voice hearers and combining it with experts in disorders such as schizophrenia, such as psychiatrists.
Epidemiology
Prevalence of hallucinations varies depending on underlying medical conditions,[76][6] which sensory modalities are affected,[7] age[77][76] and culture.[78] As of 2022,[update] auditory hallucinations are the most well studied and most common sensory modality of hallucinations, with an estimated lifetime prevalence of 9.6%.[77] Children and adolescents have been found to experience similar rates (12.7% and 12.4% respectively) which occur mostly during late childhood and adolescence. This is compared with adults and those over 60 (with rates of 5.8% and 4.8% respectively).[77][76] For those with schizophrenia, the lifetime prevalence of hallucinations is 80%[6] and the estimated prevalence of visual hallucinations is 27%, compared to 79% for auditory hallucinations.[6] A 2019 study suggested 16.2% of adults with hearing impairment experience hallucinations, with prevalence rising to 24% in the most hearing impaired group.[79]
A risk factor for multimodal hallucinations is prior experience of unimodal hallucinations.[6] In 90% cases of psychosis, a visual hallucination occurs in combination with another sensory modality, most often being auditory or somatic.[6] In schizophrenia, multimodal hallucinations are twice as common as unimodal ones.[6]
A 2015 review of 55 publications from 1962 to 2014 found 16–28.6% of those experiencing hallucinations report at least some religious content in them,[80]: 415 along with 20–60% reporting some religious content in delusions.[80]: 415 There is some evidence for delusions being a risk factor for religious hallucinations, with and 61.7% of people having experienced any delusion and 75.9% of those having experienced a religious delusion found to also experience hallucinations.[80]: 421
See also
- Hallucination (artificial intelligence)
- Phantosmia
- Pseudohallucination
- Closed-eye hallucination
- Dimethyltryptamine
- Folie à deux
- Ganzfeld effect
- Hallucinogenic fish
- Anomalous experiences
- Illusion
- Hypnagogia
- Microwave auditory effect
- Phantom eye syndrome
- Phosphene
- Prisoner's cinema
- Psychedelic experience
- Hallucinogen persisting perception disorder HPPD
- Psychotic depression
- Simulated reality
- Vision (spirituality)
- Schizophrenia
- Bicameral mentality
- Apparitional experience
- Phantom limb
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Further reading
- Johnson FH (1978). The Anatomy of Hallucinations. Chicago: Nelson-Hall. ISBN 0-88229-155-6.
- Slade PD, Bentall RP (1988). Sensory Deception: A Scientific Analysis of Hallucination. London Sydney: Croom Helm. ISBN 0-7099-3961-2.
- Aleman A, Larøi F (2008). Hallucinations: The Science of Idiosyncratic Perception. Washington, DC: American Psychological Association. ISBN 978-1-4338-0311-6.
- Sacks OW (2012). Hallucinations (1. American ed.). New York: Knopf. ISBN 978-0-307-95724-5.</ref>
External links
- Hearing Voices Network
- "Anthropology and Hallucinations; chapter from The Making of Religion". psychanalyse-paris.com. November 4, 2006. Archived from the original on May 29, 2016. Retrieved October 4, 2016.
- Hallucination: A Normal Phenomenon?
- Geometric visual hallucinations, Euclidean symmetry and the functional architecture of striate cortex