The experience of felt presence in a general population sample.

Felt presence is a widely occurring experience, but remains under-recognised in clinical and research practice. To contribute to a wider recognition of the phenomenon, we aimed to assess the presentation of felt presence in a large population sample (n = 10 447) and explore its relation to key risk factors for psychosis. In our sample 1.6% reported experiencing felt presence in the past month. Felt presence was associated with visual and tactile hallucinations and delusion-like thinking; it was also associated with past occurrence of adverse events, loneliness and poor sleep. The occurrence of felt presence may function as a marker for general hallucination proneness.

Musical hallucinations, secondary delusions, and lack of insight: results from a cohort study.

Introduction: Although musical hallucinations do not tend to be accompanied by delusions, occasionally patients persistently accuse others of being responsible for causing the music they perceive, sometimes with severe social consequences such as frequently calling the police or moving house. In this study we seek to broaden our understanding of this rare type of musical hallucination that comes with secondary delusions and lack of insight, and to explore associations, underlying mechanisms, and treatment possibilities. Methods: The present study is part of a cohort study on musical hallucinations carried out in the Netherlands from 2010 through 2023. Participants underwent testing with the aid of the MuHa Questionnaire, Launay-Slade Hallucinations Scale (LSHS), Schizotypal Personality Questionnaire (SPQ), Hamilton Depression Rating Scale (HDRS), and Mini Mental State Examination (MMSE). Additionally, they underwent a brain MRI, electroencephalogram, and audiological testing. Results: Five patients out of a group of N = 81 (6%) lacked insight and presented with secondary delusions regarding the perceived music. They were all female, of advanced age, and hearing-impaired, and were diagnosed with cognitive impairment. In three patients (60%), risperidone was started. This had a positive effect on the hallucinations and secondary delusions. Conclusion: The pathophysiological process underlying musical hallucinations is multifactorial in nature. We consider cognitive impairment the most likely contributing factor of the secondary delusions and lack of insight encountered in our patients, and antipsychotics the most beneficial treatment. On the basis of these small numbers, no definite conclusions can be drawn, so further research is needed to elucidate the underlying mechanisms and to develop evidence-based treatment methods for people experiencing this rare and debilitating combination of symptoms. Since the black box warning of risperidone cautions against the use of this drug in elderly persons with dementia, a proper comparison with the efficacy and safety of other antipsychotics for this group is paramount.

Social Deafferentation and the Relation Between Loneliness and Hallucinations.

BACKGROUND AND HYPOTHESIS: The social deafferentation hypothesis (SDA) has been proposed as an explanatory mechanism of hallucinations, based on the theory that social withdrawal triggers the initial phase of schizophrenia. The current study tests the SDA by assessing how loneliness is associated with different types of hallucinations. Under the SDA, increased loneliness is hypothesized to affect the occurrence of hallucinations that carry social meaning, but not of nonsocial hallucinations. STUDY DESIGN: As part of an online survey, 2038 adolescents and young adults from the general population (median age 21 years; 75% female) filled out the Questionnaire for Psychotic Experiences, and the shortened De Jong Gierveld Loneliness Scale. Binomial logistic regression was used to investigate the effects of loneliness severity on past month prevalence of hallucinations, and on the presence of social versus nonsocial hallucinations. STUDY RESULTS: Loneliness increased the prevalence of hallucinations across modalities in the past month. Moreover, stronger degree of loneliness increased the likelihood of hearing voices or laughter, and of hallucinating being touched. Conversely, loneliness decreased the likelihood of experiencing the nonsocial hallucination of a tingling feeling. As expected, loneliness did not increase the prevalence of experiencing nonsocial hallucinations. Surprisingly, neither was loneliness associated with experiencing felt presence. CONCLUSIONS: Our results are novel in showing that loneliness specifically increases the likelihood of hearing human sounds such as voices or laughter, or feeling a human touch. Hallucinations without social meaning were not more likely to be experienced with increasing loneliness. This forms a confirmation of the SDA.

Recreational Drug Use and Distress From Hallucinations in the General Dutch Population.

BACKGROUND AND HYPOTHESIS: Distress associated with auditory (AH) and visual (VH) hallucinations in the general population was found to be predictive of later need for mental healthcare. It is, therefore, important to understand factors relating to the distress individuals experience from their hallucinations. Hallucinations can easily occur under substance-induced states, but recreational drug use is also known as a self-medication strategy. The current study, therefore, investigated whether recreational drug use by individuals from the general population is associated with the degree of distress experienced from AH and/or VH. STUDY DESIGN: Drug use and distress severity associated with AH (N = 3.041) and/or VH (N = 2.218) were assessed by means of an online survey in the general Dutch population (>14 years of age). STUDY RESULTS: Multiple linear regression revealed that while past month consumption of alcohol was associated with less AH- and VH-related distress, past month cannabis use was associated with more AH- and VH-related distress. Furthermore, past month use of nitrous oxide was associated with more severe VH-related distress. CONCLUSION: Recreational use of alcohol, cannabis, and nitrous oxide may play important differential roles in the degree of distress associated with AH and VH in individuals from the general population. The consumption of these substances could form a potential risk factor for the development of distressing hallucinations or function as a signal marker for their occurrence. Due to the cross-sectional design of the current study, the causal relation between recreational drug use and distressing hallucinations remains to be elucidated.

Hallucinations in Hearing Impairment: How Informed Are Clinicians?

BACKGROUND AND HYPOTHESIS: Patients with hearing impairment (HI) may experience hearing sounds without external sources, ranging from random meaningless noises (tinnitus) to music and other auditory hallucinations (AHs) with meaningful qualities. To ensure appropriate assessment and management, clinicians need to be aware of these phenomena. However, sensory impairment studies have shown that such clinical awareness is low. STUDY DESIGN: An online survey was conducted investigating awareness of AHs among clinicians and their opinions about these hallucinations. STUDY RESULTS: In total, 125 clinicians (68.8% audiologists; 18.4% Ear-Nose-Throat [ENT] specialists) across 10 countries participated in the survey. The majority (96.8%) was at least slightly aware of AHs in HI. About 69.6% of participants reported encountering patients with AHs less than once every 6 months in their clinic. Awareness was significantly associated with clinicians' belief that patients feel anxious about their hallucinations (ß = .018, t(118) = 2.47, P < .01), their belief that clinicians should be more aware of these hallucinations (ß =.018, t(118) = 2.60, P < .01), and with confidence of clinicians in their skills to assess them (ß = .017, t(118) = 2.63, P < .01). Clinicians felt underequipped to treat AHs (Median = 31; U = 1838; PFDRadj < .01). CONCLUSIONS: Awareness of AHs among the surveyed clinicians was high. Yet, the low frequency of encounters with hallucinating patients and their belief in music as the most commonly perceived sound suggest unreported cases. Clinicians in this study expressed a lack of confidence regarding the assessment and treatment of AHs and welcome more information.

Occurrence and phenomenology of hallucinations in the general population: A large online survey.

Although epidemiological studies report that hallucinations occur in 6-15% of the general population, little is known about their phenomenology. To overcome this paucity, this study investigates the phenomenological characteristics of hallucinations in the general population, by using a nationally promoted online survey to assess hallucination phenomenology in four sensory modalities, through a self-report version of the Questionnaire for Psychotic Experiences (QPE), in 10,448 participants (aged 14-88 years). The phenomenology of hallucinations was assessed if hallucinations reportedly occurred in the past month. In the past month, auditory hallucinations were reported most frequently (29.5%), followed by visual (21.5%), tactile (19.9%), and olfactory hallucinations (17.3%); hallucinations in two or more modalities were reported by 47.6%. Substantial numbers of participants rated their hallucinations as severe, due to negative content (16.0-31.6%), previous bothersome experiences (14.8-20.2%), ensuing distress (10.5-16.8%), and/or ensuing disfunctioning (12.7-17.3%). Decreased insight was found in 10.2-11.4%. Hypnagogia was reported by 9.0-10.6%, and bereavement hallucinations by 2.8%. Despite a low prevalence of delusions (7.0%), these phenomena were significantly associated with recent hallucinations, observed in up to 13.4% of the participants with hallucinations during the past week (p < 0.001). Our results indicate a wide variety of the phenomenology of hallucinations in the general population and support the existence of a phenomenological continuum.

Fragmented sleep relates to hallucinations across perceptual modalities in the general population.

Although previous studies reported a link between sleep problems and the occurrence of hallucinations, more detailed information is needed to translate this association into clinical practice. This study investigates sleep quality and its relation to prevalence, type, content, and phenomenology of hallucinations, using an online survey in a large population sample (n = 10,299). Based on community-based cluster analysis, four groups could be distinguished that differed in terms of sleep quality. Our results confirm previous studies in showing that poor sleep is associated with the occurrence of hallucinations, and extend previous results on a number of aspects. First, we show that particularly fragmented sleep relates to the occurrence of hallucinations. Second, we show that this is the case for hallucinations across the auditory, visual, olfactory, and tactile domains. Third, our results show that fragmented sleep not only relates to the occurrence, but also to the content, frequency, duration, and associated distress of hallucinations. Finally, compared to poor sleep, good sleep quality is associated with hallucinations that are less negative and disruptive. We conclude that sleep hygiene measures could have a large positive impact on individuals whose fragmented sleep underlies the occurrence of bothersome hallucinations.

Spontaneous brain activity underlying auditory hallucinations in the hearing-impaired.

Auditory hallucinations, the perception of a sound without a corresponding source, are common in people with hearing impairment. Two forms can be distinguished: simple (i.e., tinnitus) and complex hallucinations (speech and music). Little is known about the precise mechanisms underlying these types of hallucinations. Here we tested the assumption that spontaneous activity in the auditory pathways, following deafferentation, underlies these hallucinations and is related to their phenomenology. By extracting (fractional) Amplitude of Low Frequency Fluctuation [(f)ALFF] scores from resting state fMRI of 18 hearing impaired patients with complex hallucinations (voices or music), 18 hearing impaired patients with simple hallucinations (tinnitus or murmuring), and 20 controls with normal hearing, we investigated differences in spontaneous brain activity between these groups. Spontaneous activity in the anterior and posterior cingulate cortex of hearing-impaired groups was significantly higher than in the controls. The group with complex hallucinations showed elevated activity in the bilateral temporal cortex including Wernicke's area, while spontaneous activity of the group with simple hallucinations was mainly located in the cerebellum. These results suggest a decrease in error monitoring in both hearing-impaired groups. Spontaneous activity of language-related areas only in complex hallucinations suggests that the manifestation of the spontaneous activity represents the phenomenology of the hallucination. The link between cerebellar activity and simple hallucinations, such as tinnitus, is new and may have consequences for treatment.

Hallucinations and other psychotic experiences across diagnoses: A comparison of phenomenological features.

Although psychotic experiences are prevalent across many psychiatric, neurological, and medical disorders, investigation of these symptoms has largely been restricted to diagnostic categories. This study aims to examine phenomenological similarities and differences across a range of diagnoses. We assessed frequency, severity and phenomenology of psychotic experiences in 350 outpatients including; participants with schizophrenia spectrum disorders, hearing impairment, Parkinson's disease, Lewy Body Dementia, Alzheimer's disease, visual impairment, posttraumatic stress disorder, borderline personality disorder, and participants with recent major surgery. Psychotic phenomena were explored between these groups using the Questionnaire for Psychotic Experiences (QPE). Participants with major psychiatric disorders reported a combination of several psychotic experiences, and more severe experiences compared to all other disorders. Participants with recent major surgery or visual impairment experienced isolated visual hallucinations. Participants with hearing impairment reported isolated auditory hallucinations, whereas the neurodegenerative disorders reported visual hallucinations, occasionally in combination with hallucinations in another modality or delusions. The phenomenology between neurodegenerative disorders, and within major psychiatric disorders showed many similarities. Our findings indicate that the phenomenology of psychotic experiences is not diagnosis specific, but may rather point to the existence of various subtypes across diagnoses. These subtypes could have a different underlying etiology requiring specific treatment.

Atopy Increases Risk of Psychotic Experiences: A Large Population-Based Study.

Introduction: Building upon the comorbidity between atopy and schizophrenia, we conducted a large cross-sectional, observational population-based study to examine if such associations also exist between atopic disorders (eczema, allergic rhinitis, and asthma) and nonclinical psychotic experiences. Methods: We examined psychotic experiences in a Dutch population sample through an online survey (≥14 years of age). Participants filled out the Questionnaire for Psychotic Experiences, together with questions screening for atopic disorders (eczema, allergic rhinitis, and asthma). Prevalence rates were calculated; binary logistic regression was used to determine odds ratios (ORs) (age, gender, and years of education as covariates). Results: We included 6,479 participants. Individuals diagnosed with one or more atopic disorders had an increased risk of psychotic experiences as compared with controls (OR = 1.26). Analysis of individual symptoms revealed an OR of 1.27 for hallucinations, whereas delusions only showed a trend. With each additional atopic disorder, the risk of psychotic experiences increased. This was also observed for hallucinations alone but not for delusions alone. Atopy was associated with hallucinations across all modalities (OR ranging from 1.19 to 1.40). These results did not appear to be driven specifically by any one of the atopic disorders. Conclusion: In the largest population sample of adolescents and adults to date, we found that atopic disorders (asthma, eczema, and allergic rhinitis) increase the risk of psychotic experiences, in a dose-response fashion. These results provide further support for the role of immunological components in the predisposition for psychosis and can serve as a base for further research.

The Questionnaire for Psychotic Experiences: An Examination of the Validity and Reliability.

Psychotic experiences are prevalent across a wide variety of psychiatric, neurological, and medical conditions. Yet current assessments are often designed for one disorder, or are limited in their examination of phenomenological features; this has hindered transdiagnostic research. This article describes an examination of the validity and reliability of the English version of a new assessment, the Questionnaire for Psychotic Experiences (QPE). This study aimed to use the QPE to examine hallucinations and delusions across a number of different conditions, and to ensure that the QPE had acceptable psychometric properties. An International Consortium on Hallucination Research working group, along with consumer groups, developed the 50-item QPE to assess the presence, severity, and phenomenology of hallucinations and delusions. Participants in the study who reported psychotic experiences included those with schizophrenia, schizoaffective disorder, bipolar affective disorder, and major depressive disorder, and those without a need for care (ie, nonclinical participants). There were 173 participants in total. Convergent and discriminant validity were assessed. Reliability was examined in terms of stability, equivalence, and internal consistency. The data confirmed that the QPE had good psychometric properties and could be put forward as an accepted measure of the transdiagnostic evaluation of psychotic experiences. Further validation is recommended with neurological and medical populations. Given its validity and reliability, comprehensive evaluation of psychotic phenomena, and relatively quick administration time, we propose that the QPE is a valuable instrument for both clinical and research settings.

Understanding hallucinations in probable Alzheimer's disease: Very low prevalence rates in a tertiary memory clinic.

INTRODUCTION: Averaging at 13.4%, current literature reports widely varying prevalence rates of hallucinations in patients with probable Alzheimer's disease (AD), and is still inconclusive on contributive factors to hallucinations in AD. METHODS: This study assessed prevalence, associated factors and clinical characteristics of hallucinations in 1227 patients with probable AD, derived from a tertiary memory clinic specialized in early diagnosis of dementia. Hallucinations were assessed with the Neuropsychiatric Inventory. RESULTS: Hallucination prevalence was very low, with only 4.5% (n = 55/1227) affected patients. Hallucinations were mostly visual (n = 40/55) or auditory (n = 12/55). Comorbid delusions were present in over one-third of cases (n = 23/55).Hallucinations were associated with increased dementia severity, neuropsychiatric symptoms, and a lifetime history of hallucination-evoking disease (such as depression and sensory impairment), but not with age or gender. DISCUSSION: In the largest sample thus far, we report a low prevalence of hallucinations in probable AD patients, comparable to rates in non-demented elderly. Our results suggest that hallucinations are uncommon in early stage AD. Clinicians that encounter hallucinations in patients with early AD should be sensitive to hallucination-evoking comorbidity.

EEG-based neurophysiological indicators of hallucinations in Alzheimer's disease: Comparison with dementia with Lewy bodies.

We studied neurophysiological indicators of hallucinations in Alzheimer's disease patients with hallucinations (ADhall+), and compared them with nonhallucinating AD (ADhall-) and dementia with Lewy bodies (DLBhall+) patients. Thirty-six matched ADhall+ and 108 ADhall- and 29 DLBhall+ patients were selected from the Amsterdam Dementia Cohort. Electroencephalography (EEG) spectral and functional connectivity (FC) analyses (phase lag index) were performed. Quantitative and visual EEG measures were combined in a random forest algorithm to determine which EEG-based variable(s) play a role in hallucinations. ADhall+ patients showed lower peak frequency (7.26 vs. 7.94 Hz, p < 0.01), α2-and ß-power, and α2-FC but higher δ-power compared to ADhall-. ADhall+ showed lower δ-power, higher ß-power, and α1-FC than DLBhall+ but did not differ in peak frequency (7.26 vs. 6.95 Hz), θ- or α-power. ADhall+ patients could be differentiated from ADhall- and DLBhall+ with a weighted accuracy of 71% with α1-power and 100% with ß-FC, the 2 most differentiating features. In sum, EEG slowing and decrease in α1-and ß-band activity form potential neurophysiological indicators of underlying cholinergic deficiency in ADhall+ and DLBhall+.

Increased risk of psychosis in patients with hearing impairment: Review and meta-analyses.

Several studies suggest hearing impairment as a risk factor for psychosis. Hearing impairment is highly prevalent and potentially reversible, as it can be easily diagnosed and sometimes improved. Insight in the association between hearing impairment and psychosis can therefore contribute to prevention of psychosis. This paper provides meta-analyses of all epidemiologic evidence on the association between hearing impairment and psychosis and summarizes mechanisms that potentially underlie this relationship. Meta-analyses showed an increased risk of hearing impairment on all psychosis outcomes, such as hallucinations (OR 1.40(95%CI 1.18-1.65; n=227,005)), delusions (OR 1.55(95%CI 1.36-1.78; n=250,470)), psychotic symptoms (OR 2.23(95%CI 1.83-2.72; n=229,647) and delirium (OR 2.67(95%CI 2.05-3.48; n=12,432). Early exposure to hearing impairment elevated the risk of later development of schizophrenia (OR 3.15(95%CI 1.25-7.95; n=50,490)). Potential mechanisms underlying this association include loneliness, diminished theory of mind, disturbances of source monitoring and top-down processing and deafferentiation. Early assessment and treatment of hearing impairment in patients with (high risk of) psychosis may be essential in psychosis treatment and prevention.