Prevalence of hallucinations and their pathological associations in the general population
Introduction
Descriptions of hallucinatory phenomena have figured prominently in written documents since the beginning of recorded history. The word ‘hallucinatory’ has its roots in the Latin hallucinari or allucinari, which means to wander in mind. Lavater introduced ‘hallucination’ in the English language in 1572 to refer to ‘ghostes and spirites walking the nyght.’ The word was first used in its current sense by Jean Etienne Esquirol in 1837. In the Middle Ages, hallucinations were thought to be manifestations of demons or angels. A religious person who experienced such phenomena was seen as a saint, whereas a commoner was believed to be possessed by the devil. In certain cultures today, hallucinations are still perceived as the work of Satan or as a result of magic (Wahass and Kent, 1997).
Normally, hallucinations are perceptions that occur in the absence of corresponding sensory stimuli. From the subjective point of view of the individual who experiences these phenomena, they are indistinguishable from normal perceptions. Something is perceived yet, objectively, there is nothing to perceive. In this sense, hallucinations are different from illusions, which are distortions or misperceptions of a perceivable object. However, people having hallucinations are confronted by other people dismissing their perceptions. Therefore, the estimation of hallucinations in the general population is based on people having experienced perceptions not confirmed by others.
In the general population, using the data from the NIMH epidemiological catchment area survey, Tien (1991) found an incidence of visual hallucinations of 2% among men and 1.3% among women. In a comparative study of hallucinations in the general population and among schizophrenics, Lindal et al. (1994) observed that the former mainly reported visual hallucinations involving persons, whereas the latter were more likely to report other types of hallucinations. However, schizophrenia is relatively infrequent in the general population. In the United States, the Epidemiological Catchment Area study (Regier et al., 1988) found a lifetime prevalence of schizophrenia of 1.5%. This prevalence was 0.7% in the National Comorbidity Survey (Kendler et al., 1996). An Israeli survey found a prevalence of 0.7% in individuals aged 35–45 years (Levav et al., 1993). Therefore, It appears that the prevalence of reported hallucinations has rarely been assessed in the general population. Furthermore, the association between hallucinations and their causes, namely organic pathologies and psychoactive substances, has never been explored in subjects in the general population.
The purpose of this study is to provide additional data on the prevalence of hallucinations in the general population of three European countries and to study their association with organic diseases, mental disorders and psychoactive substance use.
Section snippets
Sample
The samples are composed of respondents from three countries: the United Kingdom, Germany and Italy. The UK study was undertaken in 1994 with a representative sample of 4972 individuals from the non-institutionalized general population aged 15 years or over. The German study was carried out in 1996 and involved 4115 like individuals. The Italian survey was conducted in 1997 and involved 3970 like individuals.
Each sample was drawn using a two-stage sampling design. At the first stage, official
Results
The overall sample consisted of 6263 (48%) men and 6794 (52%) women ranging in age from 15 to 100 years, with no differences across countries.
Based on the report of current and past medical consultations, a conservative estimate of 0.5% was calculated for the lifetime prevalence of psychotic disorders in this sample. There were no significant differences across the countries. Prevalence rates were comparable in terms of gender and age.
Discussion
The purpose of this study was to investigate hallucinatory phenomena in the general population of three European countries (Germany, Italy and the United Kingdom), taking into account all possible causes. Aside from psychotic disorders, many other conditions may trigger hallucinatory phenomena, namely, use of drugs such as cocaine and opiates, brainstem pathology, neurological diseases and other mental disorders such as mood disorders. Certain hallucinations can be considered normal phenomena.
Acknowledgements
This study was supported by grants from the Fonds de la Recherche en Santé du Québec (#971067) and the Sanofi-Synthelabo Group.
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