"Normal" people and the general population

Barret T.R and Etheridge J.B (1992) Verbal hallucinations in Normals I: People who hear voices Applied Cognitive Psychology, Vol. 6, pp. 379-387

Vanessa Beavan, John Read and Claire Cartwright (2006)Angels at our tables: A summary of the findings from a 3-year research project into New Zealanders’ Experiences of Hearing Voices, University of Auckland, New Zealand
Full paper here

Brugger, Peter; Regard, Marianne; Landis, Theodor; Oelz, Oswald (1999) Hallucinatory Experiences in Extreme-Altitude Climbers Neuropsychiatry, Neuropsychology, & Behavioral Neurology, Jan. 1999, 12 (1), 67–71

This study attempted a systematic investigation of incidence, type, and circumstances of anomalous perceptual experiences in a highly specialized group of healthy subjects, extreme-altitude climbers.
There is anecdotal evidence for a high incidence of anomalous perceptual experiences during mountain climbing at high altitudes.
In a structured interview, we asked eight world-class climbers, each of whom has reached altitudes above 8500 m without supplementary oxygen, about hallucinatory experiences during mountain climbing at various altitudes. A comprehensive neuropsychological, electroencephalographic, and magnetic resonance imaging evaluation was performed within a week of the interview (8).
All but one subject reported somesthetic illusions (distortions of body scheme) as well as visual and auditory pseudohallucinations (in this order of frequency of occurrence). A disproportionately large number of experiences above 6000 m as compared to below 6000 m were reported (relative to the total time spent at these different altitudes). Solo climbing and (in the case of somesthetic illusions) life-threatening danger were identified as probable triggers for anomalous perceptual experiences. No relationship between the number of reported experiences and neuropsychological impairment was found. Abnormalities in electroencephalographic (3 climbers) and magnetic resonance imaging (2 climbers) findings were likewise unrelated to the frequency of reported hallucinatory experiences.
The results confirm earlier anecdotal evidence for a considerable incidence of hallucinatory experiences during climbing at high altitudes. Apart from hypoxia, social deprivation and acute stress seem to play a role in the genesis of these experiences.

Bentall R.P., Claridge G.S. & Slade P.D (1989): The Multidimensional Nature of Schizotypal traits: A factor analytic study with normal subjects, British Journal of Clinical Psychology, Vol.?

Chedru F, Feldman F, Ameri A, Sales J, Roth M. Visual and Auditory Hallucinations in A Psychologically Normal Woman Lancet, Sept. 28 1996, 348(9031):896

Tony David, Ivan Leudar (May 2001): Head to head: Is hearing voices a sign of mental illness, The Psychologist vol 14, no 5, pp 256-259

Martin F. Davies, Murray Griffin and Sue Vice Affective reactions to auditory hallucinations in psychotic, evangelical and control groups British Journal of Clinical Psychology, 40, 361–370

Objectives. Building on recent work on the similarities and differences in delusional ideation between psychotic and religious populations (Peters, Day, 1999), the experiences of auditory hallucinations in psychotic,evangelical and control groups were examined in this study.

Method. The incidence and subjective experiences of hearing voices were assessed using questionnaire methods in psychotic out-patients, evangelical Christians and controls (non-psychotic, non-evangelical).

Results. Incidence of auditory hallucinations differed significantly across the three groups with psychotics showing the highest levels and controls the lowest levels. The experiences of the evangelical group were significantly more positive than those of the control group, which in turn were significantly more positive than those of the psychotic group. The most recent experience of hearing voices was rated more positively than the first experience by the psychotic and religious groups but not by the control group. These findings were much stronger for affective reactions to the experiences than for perceptions of the voices.

Conclusion. These results provide only partial support for the findings of Peters et al. (1999) on differences in delusional ideation and possible reasons for this are discussed. The findings for religious and psychotic individuals are discussed further in terms of interpretational and coping mechanisms.

Eaton W.W., Romanoski A., Anthony J.C., Nestadt G. (1991), Screening for psychosis in the general population with a self report interview, Journal of Nervous and Mental Disease, No. 179, pp 689 693

Feelgood, S. R. and Rantzen, A. J. Auditory and Visual Hallucinations in University Students Personality and Individual Differences, 1994, Vol. 17 (2): 293-296

One-hundred and thirty-six univeristy students were administered the Launay-Slade Hallucination Scale (LSHS). Low and high scorers then completed a visual and an auditory task that utilized non-hypnotic suggestion and ambiguous stimuli. The high LSHS group reported a significantly greater number of meaningful visual and auditory experiences in response to the ambiguous stimulation. It is argued that these phenomena are hallucinations and demonstrate the possibility of researching hallucinations in non-psychotic populations in a laboratory setting.

Garrido, Eduardo; Javierre, Casimiro; Ventura, Josep L; Segura, Ramon Hallucinatory Experiences at High Altitude Neuropsychiatry, Neuropsychology, & Behavioral Neurology, April 2000, 13 (2), 148–148

Honig, A.; Romme. M.; Ensink, B.; Escher, S.; Pennings, M.; Devries, M.W. (1998): Auditory Hallucinations: A Comparison between Patients and Nonpatients. The Journal of Nervous and Mental Disease, 186 (10), 646-651

The form and the content of chronic auditory hallucinations were compared in three cohorts, namely patients with schizophrenia, patients with a dissociative disorder, and nonpatient voice-hearers. The form of the hallucinatory experiences was not significantly different between the three groups. The subjects in the nonpatient group, unlike those in the patient groups, perceived their voices as predominantly positive: they were not alarmed or upset by their voices and felt in control of the experience. In most patients, the onset of auditory hallucinations was preceded by either a traumatic event or an event that activated the memory of earlier trauma. The significance of this study is that it presents evidence that the form of the hallucinations experienced by both patient and nonpatient groups is similar, irrespective of diagnosis. Differences between groups were predominantly related to the content, emotional quality, and locus of control of the voices. In this study the disability incurred by hearing voices is associated with (the reactivation of) previous trauma and abuse.

Johns LC, Nazroo JY, Bebbington P, Kuipers E. (2002) Occurrence of hallucinatory experiences in a community sample and ethnic variations. The British Journal of Psychiatry 180: 174-178

Hallucinations typically are associated with severe psychiatric illness but also are reported by individuals with no psychiatric history. AIMS: To examine the prevalence of hallucinations in White and ethnic minority samples using data from the Fourth National Survey of Ethnic Minorities.
Interviews of 5196 ethnic minority and 2867 White respondents were carried out. The respondents were screened for mental health problems and the Psychosis Screening Questionnaire asked about hallucinations. Those who screened positive underwent a validation interview using the Present State Examination.
Four per cent of the White sample endorsed a hallucination question. Hallucinations were 2.5-fold higher in the Caribbean sample and half as common in the South Asian sample. Of those who reported hallucinatory experiences, only 25% met the criteria for psychosis.
The results provide an estimate of the annual prevalence of hallucinations in the general population. The variation across ethnic groups suggests cultural differences in these experiences. Hallucinations are not invariably associated with psychosis.

Kotsopoulos, S., Kanigsberg, J., Cote, A., Fiedorowicz, C., Hallucinatory Experiences in Nonpsychotic Children Journal of the American Academy of Child & Adolescent Psychiatry, May 1987, 26 (3), 375–380

McCreery, C. and Claridge, G. A Study of Hallucinations in Normal Subjects Personality and Individual Differences, 1996, 21 (5): 739-747

A group of 20 subjects who reported previously experiencing at least one ‘out-of-the-body’ experience (OBE) and a group of 20 matched controls attempted to induce OBEs in the laboratory under conditions of mild sensory limitation and physical relaxation. As predicted, the OBErs were more prone than controls to report hallucinations and involuntary imagery in this situation. The reporting of anomalous perceptual experiences was also positively correlated with scores on schizotypy scales, which measure the incidence of ‘positive’ symptomatology at a sub-clinical level. The results are interpreted in terms of a model of the ‘happy schizotype’—a relatively well-adjusted person who is functional despite, and in some cases even because of, his or her anomalous perceptual experiences.

Morrison A.P.; Wells A.; Nothard S. Cognitive and emotional predictors of predisposition to hallucinations in non-patients. British Journal of Clinical Psychology, Volume 41, Number 3, September 2002 , pp. 259-270(12)

This study adapted the Launay Slade Hallucination Scale (LSHS) to measure predisposition to auditory and visual hallucinations and examine the relationship between meta-cognition and predisposition in a non-psychiatric population. It also tested the hypothesis that individuals highly predisposed to hallucination would show positive and negative meta-cognitive beliefs and report the use of different thought control strategies.
A within participants correlational design was employed. Methods. A revised LSHS was administered to 105 normal participants who were also asked to complete questionnaires assessing paranoia, meta-cognitive beliefs, thought control strategies, anxiety, depression and beliefs about unusual perceptual experiences.
Results. Two empirically distinct but correlated hallucinatory traits (auditory and visual) were measured by the modified LSHS. Consistent with predictions, it was found that positive beliefs about unusual perceptual experiences were the best predictor of predisposition to auditory and visual hallucinations and that those participants who scored higher on predisposition to hallucination used diåerent thought control strategies and had diåerent negative meta-cognitive beliefs in comparison with participants of low predisposition.
Meta-cognitive beliefs about thoughts and hallucinatory phenomena appear to be implicated in predisposition to hallucination. The theoretical and clinical implications of the findings are discussed.

Pearson, D., Burrow, A., FitzGerald, C., Green, K., Lee, G., Wise, N. (2007) Auditory Hallucinations in Normal Child Populations Personality & Individual Differences, Aug. 2001, Special Issue, 31(3), 401 -407

Posey T.B. and Losch M.E. (1984), Auditory hallucinations of hearing voices in 375 normal subjects Imagination, Cognition and Personality, vol 3, no.2, pp. 99 113

Rector and Seeman (1992): Auditory Hallucinations in Women and Men, Schizophrenia Research, vol 7, pp. 233 236

Rodrigo, A.M.L., Pineiro, M.M.P., Suarez, P.C.M., Caro, M.I., and Giraldez, S.L. Hallucinations in A Normal Population: Imagery and Personality Influences Psychology in Spain, 1997, Vol. 1. No 1, 10-16

Abstract The present study was designed to gather data related to the continuum hypothesis of hallucinations. According to this hypothesis, hallucinations can be considered to be one end of a continuum of normal conscious experience that include vivid imagery, daydreams, and thoughts. Subjects were 222 college students who anonymously completed the Hallucination Questionnaire (Barrett and Etheridge, 1994), the Betts QMI Vividness of Imagery Scale (Richardson, 1969), and Millon’s Clinical Multiaxial Inventory (MCMI-II) (Millon, 1983). The results suggest that hallucinators have more vivid imagery and higher scores on most Millon’s Inventory scales compared to non-hallucinators. Nevertheless, a normal distribution of the hallucinatory experiences was not found, which casts doubt on their dimensional nature.

Schreier, H. A. Hallucinations in Nonpsychotic Children: More Common Than We Think? Journal of the American Academy of Child & Adolescent Psychiatry, May 1999, 38 (5), 623–625

Sidgewick H.A. (1894) Report on the census of hallucinations, Proceedings of the Society of Psychical Research, No. 26, pp. 25 394

Tien A.Y. (1991) Distributions of hallucinations in the population Social Psychiatry and Psychiatric Epidemiology, No.26, pp. 287 292

John Watkins: Hearing voices – A Common Human Experience: published in 1998 by Hill of Content Publishing, Melbourne, Australia, ISBN 0-85572-288-6

J. Watkins; M. Romme; S. Escher (2003). Hearing voices: A common human experience. Nordic Journal of Psychiatry, Volume 57, Issue 2 March 2003 , pages 157 – 159

J. van Os, H. Verdoux, S. Maurice-Tison, B. Gay, F. Liraud, R. Salamon, M. Bourgeois (1999). Self-reported psychosis-like symptoms and the continuum of psychosis; Social Psychiatry and Psychiatric Epidemiology, Issue Volume 34, Number 9 / October, 1999

Background: It has been suggested that psychotic symptoms may be distributed along a continuum that extends from normality through depressive states to schizophrenia with increasing level of severity. This study examined the hypothesis that the severity of positive psychotic symptoms increases from normality, through depression/anxiety states to clinical psychosis.

Vickers, B., Garralda, E. (2000) Hallucinations in Nonpsychotic Children Journal of the American Academy of Child & Adolescent Psychiatry, Sept. 2000, 39 (9), 1073

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