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4 Psychotic Hallucinations Richard P. Bentall and Filippo Varese Hallucinations, especially in the auditory modality (hearing voices), are a common symptom of mental illness and are usually associated with the diagnosis of schizophrenia . Hence various types of hallucinatory experience—for example, audible thoughts or voices heard commenting on one’s actions—were famously included in the German psychiatrist Kurt Schneider’s (1959) list of “first-rank symptoms” of the disorder. Apparently consistent with Schneider’s view, studies have consistently shown that most patients diagnosed as schizophrenic report hallucinatory experiences (Sartorius et al., 1986). For example, in a recent clinical trial conducted with patients suffering from early schizophrenia in the United Kingdom (Tarrier et al., 2004), 177 out of 255 (69 percent) of patients complained of hearing voices. It is sometimes forgotten that this association occurs not because schizophrenia causes hallucinatory voices but because, following Schneider, we define schizophrenia in this way. Many modern psychopathologists are turning their backs on the schizophrenia concept, arguing that it is too hopelessly vague to be useful clinically or scientifically, that it lumps together patients with diverse problems, and that, as a diagnosis, it does not make useful predictions about the course of illness (whether or not the patient will get better) or which kinds of treatment are most likely to be effective (see Bentall, 2003). Data on hallucinations illustrate some of these difficulties. For example, hallucinations are experienced by approximately 10 percent of patients diagnosed as suffering from bipolar disorder (Goodwin & Jamison, 1990) and also sometimes by patients suffering from major depression (Coryell, 1996; Lattuada, Serretti, Cusin, Gasperini, & Smeraldi, 1999). More surprisingly to many both inside and outside the mental health community, hallucinations are also reported by a sizable minority of individuals who have never had contact with psychiatric services. The earliest evidence that this was the case emerged from surveys conducted for the purposes of psychical research (Sidgewick, 1894; West, 1948), and similar findings were later reported in studies of selected groups, especially undergraduate students (Barrett & Etheridge, 1992; Bentall & Slade, 1985b). More recently these observations have been supported by data from more carefully conducted epidemiological investigations. 66 R. P. Bentall and F. Varese For example, in the Epidemiological Catchment Area Study, in which approximately 18,000 people drawn at random from the U.S. population were interviewed about psychiatric symptoms, the annual incidence rate for hallucinations (the numbers experiencing hallucinations during the year of study) was estimated at between 4 and 5 percent, and the lifetime prevalence rate was estimated at between 10 and 15 percent (Tien, 1991). In a study of 7,000 randomly selected Dutch citizens, 7.9 percent had experienced hallucinations (van Os, Hanssen, Bijl, & Ravelli, 2000), and in the more recent U.S. National Comorbidity Study of 8,000 U.S. citizens, 8.5 percent had experienced auditory hallucinations, 7 percent had experienced visual hallucinations, 7 percent had experienced tactile hallucinations, and 1.6 percent had experienced all three kinds (Shevlin, Dorahy, & Adamson, 2007). These figures compare with an estimated lifetime risk of being diagnosed as schizophrenic of about 0.5 percent (Jablensky , 1995; McGrath, 2005). Hence we can roughly estimate that for every schizophrenia patient who hears voices there are about ten voice hearers who do not seek psychiatric treatment. What are we to make of these findings? One response long favored by psychologists and an increasing minority of psychiatrists has been to view schizophrenia or psychosis (a collective term used to describe all serious mental disorders in which the individual seems, in some sense, to lose touch with reality) as existing on a continuum with normal functioning (Claridge, 1987; van Os et al., 2000). According to this view, the human world is not divided into those who are schizophrenic and those who are not; rather, a continuum runs from ordinary functioning, through frank eccentricity, to full-blown madness. However, given the increasing doubts about the value of categorical diagnoses such as schizophrenia, and given that patients with many diagnoses experience hallucinations, an alternative approach is to try to study and explain hallucinations in their own right. 1 The Phenomenology of Psychotic Hallucinations A starting point is to understand their phenomenology. A widely cited definition of hallucinations holds that they are percept-like experiences that occur in the absence of appropriate stimuli, which have the full force and impact of corresponding real perceptions and are not amenable to voluntary control (Slade & Bentall, 1988). Since the early nineteenth century, hallucinations have been distinguished from illusions, in which real objects are...

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