Auditory Hallucinations in Deaf Individuals: Exploring Causes and Characteristics
Similar to visual hallucinations in visually impaired patients, auditory hallucinations are often suggested to occur in adults with hearing impairment. However, research on this association is limited. This article delves into the prevalence, characteristics, and potential causes of auditory hallucinations in deaf individuals, drawing on recent studies and expert insights.
Prevalence of Auditory Hallucinations in Hearing-Impaired Individuals
Hallucination presence was determined in 1007 subjects aged 18-92, who were referred for audiometric testing to the Department of ENT-Audiology, University Medical Center Utrecht, the Netherlands. Out of 829 participants with hearing impairment, 16.2% (n = 134) had experienced auditory hallucinations in the past 4 weeks; significantly more than the non-impaired group [5.8%; n = 10/173; p < 0.001, odds ratio 3.2 (95% confidence interval 1.6-6.2)]. Prevalence of auditory hallucinations significantly increased with categorized severity of impairment, with rates up to 24% in the most profoundly impaired group (p < 0.001). The corrected odds of hallucination presence increased 1.02 times for each dB of impairment in the best ear. These findings reveal that auditory hallucinations are common among patients with hearing impairment, and increase with impairment severity.
One study involving individuals who had experience of hallucinations revealed that 16.2% of participants with impaired hearing hallucinated in the last 4 weeks.
The Nature of Hallucinations in Deaf Individuals
A new UCL study, published in the July 2007 issue of Cognitive Neuropsychiatry, systematically explores the perceptual characteristics of voice hallucinations in deaf people with schizophrenia for the first time. Earlier research had suggested that born-profoundly deaf people might experience true auditory hallucinations. However, the collection and interpretation of data had relied on non-native signers or hearing researchers using sign language interpreters. This study breaks new ground by using more ecologically valid methodology to confirm that true auditory hallucinations were confined to deaf individuals who are some point in their lives had experienced hearing.
Dr Atkinson, who is herself a deaf British Sign Language (BSL) user, aimed to elucidate the variety of voice hallucination perceived by deaf people: "Particular attention was paid to deconstructing concepts that might be misconstrued as truly auditory to those unfamiliar with the subtleties of BSL and deaf conceptualisations of sound-based phenomena. Deaf people frequently use signs such as 'heard', 'shout', 'voices' and 'talk' without necessarily bestowing the auditory qualities assumed in English. Concepts such as 'loud' may be understood as being highly intrusive and difficult to ignore rather than as high auditory volume.
All the participants had a primary medical diagnosis of schizophrenia, had permanent deafness (either congenital or acquired) and clear recollection of their voice hallucinations over the past two years. Hearing loss among the participants ranged from mild to profound. Dr Atkinson's team then collated the results into five factors according to their perceptions. Participants born profoundly deaf reported non-auditory, clear and easy to understand voices. They were all confident that they did not hear any sounds, but knew the gender and identity of the voice. They reported seeing an image of the voice signing or lips moving in their mind.
By contrast, only participants who had early experience of hearing speech described their experiences in auditory terms. Others with partial awareness of sound were uncertain whether they were really hearing sound when the voices were present. Individuals with severe language deprivation and incomplete acquisition of either speech or sign, were remarkable in that they did not experience either auditory characteristics or perception of subvisual imagery of voice articulation, suggesting that language acquisition within a critical period may be necessary for voice-hallucinations that are organised in terms of how spoken or signed utterances are articulated.
Dr Atkinson concluded: "The results support the notion that the perceptual characteristics of voice-hallucinations map closely onto an individual's real life communication preferences and experience of language and sound. The methodology demonstrates that the diversity of voice hallucination experience reflects the variety of experience with language and hearing loss among deaf individuals.
The Link Between Hearing Loss and Psychosis
Psychosis can be a debilitating symptom of various mental illnesses, causing hallucinations and delusions that interfere with a person’s day-to-day living and quality of life. Studies have shown that hearing impairment increases the risk of psychosis. For example, hearing loss at an early age has been associated with an increased risk of developing schizophrenia at a later age.
So, how are hallucinations and delusions shaped by the experience of deafness? Dr Blazer, who recently published a review titled “The Silent Risk for Psychiatric Disorders in Late Life,” says, “When we have problems hearing, we are more apt to misinterpret our environment. The social environment may then appear more threatening and less understandable." However, he emphasizes that while this mechanism certainly leads to delusions, it doesn’t specifically lead to hallucinations.
Hallucinations relate to an inability to distinguish between conscious sensory experiences and memory-based sensory perceptions. Delusions, on the other hand, occur when a person holds onto inaccurate or false beliefs despite being shown evidence to contradict those beliefs. In Dr Blazer’s review, the focus was on psychosis risk among the elderly. The prevalence of hearing loss increases as people age. The World Health Organization estimates that 5% of the world’s population has some form of hearing loss. In the United States, 75% of people aged ≥70 years have hearing impairment. With an aging American population, Dr Blazer considers hearing loss a silent epidemic linked with delusions among the elderly.
Researchers typically characterize hallucinations and delusions according to content. Studies reveal that the content of auditory hallucinations among hearing-impaired persons varies greatly. Hallucinations and delusions are also typically defined by topographical characteristics.
When asked about the topography of hallucinations and delusions among deaf adults diagnosed with psychosis, Dr Blazer says, “After all these years, we actually don’t have an answer to this.” So far, studies provide limited information on a few topographical components such as frequency and loudness. For example, one study showed that auditory hallucinations increased as the severity of hearing loss increased. More than 16% of participants with hearing loss experienced hallucinations in the previous month.
Misinterpretations and the Need for Improved Understanding
An improved understanding of the content and topography of hallucinations among individuals who are deaf is particularly important since clinicians have made some misinterpretations with regard to deaf people’s experiences of hallucinations. For instance, individuals who have been completely deaf since birth have been reported as having “heard” voice hallucinations. However, recent studies have shown that the confusion emerges from the complexity of understanding the unique experience of a deaf person.
People who have been completely deaf since birth cannot experience true auditory hallucinations. Rather, they experience visual or physical hallucinations such as moving lips, sign language movements, body motions, and facial expressions that they interpret as an expression of the voice. The loss in translation happens when deaf people need to borrow sound-related terminology or hand gestures to communicate with interpreters or psychiatrists who can hear.
Misinterpretations in our understanding of psychotic experiences among those with impaired hearing illustrate a need for improved care for this group. Early diagnosis and treatment of hearing loss is also important to help prevent psychosis.
According to Dr Blazer, “The mental health worker who is working with a patient with hearing loss should determine if more could be done to improve the patient’s hearing. Dr Blazer points out that new scientific papers have filled some of the knowledge gaps in the association between psychosis and hearing impairment. However, more data about this phenomenon and its confounding factors are needed.
“First, it would be good to know whether improving hearing, such as with a good hearing aid or a cochlear implant, would decrease the risk of psychoses [for those who develop hearing loss in later life and for those who struggle with sign language and attempt to communicate verbally],” he says. More robust data on the topography and content of hallucinations and delusions can reveal how psychosis is shaped by experiences that are unique to those with a hearing impairment.
Table 1: Prevalence of Auditory Hallucinations Based on Hearing Impairment Severity
| Severity of Hearing Impairment | Prevalence of Auditory Hallucinations |
|---|---|
| Non-impaired | 5.8% |
| Hearing Impairment | 16.2% |
| Profoundly Impaired | Up to 24% |