[2] However, individuals without any psychiatric disease whatsoever may hear voices,[3] including those under the influence of mind-altering substances, such as cannabis, cocaine, amphetamines, and PCP.
These hallucinations can be caused by: lesions on the brain stem (often resulting from a stroke), sleep disorders such as narcolepsy, tumors, encephalitis, or abscesses.
[8] In the past, the cause of auditory hallucinations was attributed to cognitive suppression by way of executive function failure of the frontoparietal sulcus.
[9] It is assumed through research that the neural pathways involved in normal speech perception and production, which are lateralized to the left temporal lobe, also underlie auditory hallucinations.
[16] In schizophrenia, people show a consistent increase in activity of the thalamic and striatal subcortical nuclei, hypothalamus, and paralimbic regions; confirmed by PET and fMRI scans.
[21] Auditory verbal hallucinations attributed to an external source, rather than internal, are considered the defining factor for the diagnosis of schizophrenia.
[citation needed] The voices heard are generally destructive and emotive, adding to the state of artificial reality and disorientation seen in psychotic patients.
The glutamate hypothesis, proposed as a possible cause for schizophrenia, may also have implications in auditory hallucinations, which are suspected to be triggered by altered glutamatergic transmission.
A study conducted by the La Trobe University School of Psychological Sciences revealed that as few as five cups of coffee a day could trigger the phenomenon.
[28] Intoxication of psychoactive drugs such as PCP, amphetamines, cocaine, marijuana and other substances can produce hallucinations in general, especially in high doses.
Extreme altitude Mountain climbers, especially lone ones, can experience auditory hallucinations due to a combination of hypoxia, social isolation and stress.
[31] Cognitive behavioral therapy has been shown to help decrease the frequency and distressfulness of auditory hallucinations, particularly when other psychotic symptoms were presenting.
It has been seen in patients with schizophrenia and auditory hallucinations that therapy might help confer insight into recognising and choosing to not obey the voices that they hear.
Transcranial magnetic stimulation when used to treat auditory hallucinations in patients with schizophrenia is done at a low frequency of 1 Hertz to the left temporoparietal cortex.
"[39][40] The oracles of ancient Greece were known to experience auditory hallucinations while breathing in certain psychoactive vapors (such as the smoke from bay leaves), while the more pervasive delusions and symptomatology were often viewed as possession by demonic forces as punishment for misdeeds.
Soon, this gave way to brain-specific treatments with the most famous examples including lobotomy, shock therapy, and branding the skull with a hot iron.
[42] They formed a major component of Bill Pohlad's Love & Mercy (2014), a biographical film which depicts Wilson's hallucinations as a source of musical inspiration,[43] constructing songs that were partly designed to converse with them.
Patients have described an interest in psychic phenomena progressing to increasingly unusual preoccupations and then to bizarre beliefs "in which I believed wholeheartedly".
In many cases, the delusional beliefs could be seen as fairly rational explanations for abnormal experiences: "I increasingly heard voices (which I'd always call 'loud thoughts')...
A 2015 published study, "Hearing Voices in Different Cultures: A Social Kindling Hypothesis" compared the experiences of three groups of 20 participants who met the criteria for schizophrenia (n = 60) from three places, including San Mateo, California (USA), Accra, Ghana (Africa), and Chennai, India (South Asia).
In a qualitative study of 57 self-identified Māori participants subcategorized within one or more of the following groups including: "tangata Māori (people seeking wellness/service users), Kaumatua/Kuia (elders), Kai mahi (cultural support workers), Managers of mental health services, clinicians (psychiatrists, nurses, and psychologists) and students (undergraduate and postgraduate psychology students)", researchers interviewed participants and asked them about "[1] their understanding of experiences that could be considered to be psychotic or labelled schizophrenic, [2] what questions they would ask someone who came seeking help and [3] they we asked about their understanding of the terms schizophrenia and psychosis".
[51] The researchers further articulate that these findings may be due to culturally specific meaning created about the experience of schizophrenia, psychosis, and hearing voices as well as "positive expectations around recovery".
[48] According to a literature review, "The prevalence of voice-hearers in the general population: A literature review", which compared 17 studies on auditory hallucinations in participants from nine countries, found that "differences in the prevalence of [voice-hearing in the adult general population] can be attributed to true variations based on gender, ethnicity and environmental context".
The external origins vary in the patients' description: some hear the voice in front of their ears, some attribute the ambient surrounding noise, like running water or wind, as the source.
[55] According to a phenomenological study conducted by Tony Nayani and Anthony David in 1996, about half of the patients (46%) with audible thoughts claimed that the hallucination has somehow taken the place of their conscience in making decisions and judgement.
[57] Historically, experiencing hallucinations as external has been understood to indicate a more severe psychopathology, but the empirical support for such a conclusion is lacking.
[63] There is on-going research that supports the prevalence of auditory hallucinations, with a lack of other conventional psychotic symptoms (such as delusions, or paranoia), particularly in pre-pubertal children.
Differentiating actual auditory hallucinations from "sounds" or a normal internal dialogue is important since the latter phenomena are not indicative of mental illness.
Such methods allowed researchers to find a correlation between a decreased gray matter of the left temporal lobe and difficulties in processing external sound stimuli in hallucinating patients.
It is suspected that deficits in the left temporal lobe attribute that lead to spontaneous neural activity cause speech misrepresentations that account for auditory hallucinations.