Delusions in the nonclinical population

Department of Psychology, PO Box 77, Institute of Psychiatry, Kings College London, Denmark Hill, London SE5 8AF, UK.
Current Psychiatry Reports (Impact Factor: 3.24). 06/2006; 8(3):191-204. DOI: 10.1007/s11920-006-0023-1
Source: PubMed


Delusions have long been considered a hallmark of psychotic disorders such as schizophrenia. However, delusions may only be most visibly present in psychotic conditions and could also occur in nonclinical groups. The aim of this review is to establish whether delusions, as traditionally considered and assessed in psychiatric conditions, are also present in individuals without a psychiatric or neurologic condition. Clear evidence is found that the rate of delusional beliefs in the general population is higher than the rate of psychotic disorders and that delusions occur in individuals without psychosis. The frequency of delusional beliefs in nonclinical populations varies according to the content of the delusion studied and the characteristics of the sample population. Approximately 1% to 3% of the nonclinical population have delusions of a level of severity comparable to clinical cases of psychosis. A further 5% to 6% of the nonclinical population have a delusion but not of such severity. Although less severe, these beliefs are associated with a range of social and emotional difficulties. A further 10% to 15% of the nonclinical population have fairly regular delusional ideation. There is convincing evidence that delusional ideation, delusions, and clinically severe delusions are related experiences. Information about clinical delusions can therefore be obtained by studying delusional ideation in nonclinical populations.

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    • "A hubris account of paranoia Delusions are traditionally associated with schizophrenia but are in fact a transdiagnostic, symptom, which are present in many psychiatric disorders. Benign subclinical paranoid beliefs are encountered in 15-20% of the population (Freeman, 2006; Stip & Letourneau, 2009; van Os & Kapur, 2009). "
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    ABSTRACT: Overconfidence in errors is a well-replicated cognitive bias in psychosis. However, prior studies have sometimes failed to find differences between patients and controls for more difficult tasks. We pursued the hypothesis that overconfidence in errors is exaggerated in participants with a liability to psychosis relative to controls only when they feel competent in the respective topic and/or deem the question easy. Whereas subjective competence likely enhances confidence in those with low psychosis liability as well, we still expected to find more 'residual' caution in the latter group. We adopted a psychometric high-risk approach to circumvent the confounding influence of treatment. A total of 2321 individuals from the general population were administered a task modeled after the "Who wants to be a millionaire" quiz. Participants were requested to endorse one out of four response options, graded for confidence, and were asked to provide ratings regarding subjective competence for the knowledge domain as well as the subjective difficulty of each item. In line with our assumption, overconfidence in errors was increased overall in participants scoring high on the Paranoia Checklist core paranoia subscale (2 SD above the mean). This pattern of results was particularly prominent for items for which participants considered themselves competent and which they rated as easy. Results need to be replicated in a clinical sample. In support of our hypothesis, subjective competence and task difficulty moderate overconfidence in errors in psychosis. Trainings that teach patients the fallibility of human cognition may help reduce delusional ideation. Copyright © 2015. Published by Elsevier Ltd.
    Full-text · Article · Dec 2015 · Journal of Behavior Therapy and Experimental Psychiatry
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    • "Interestingly, there is converging evidence that such unfounded beliefs in the healthy lie on a continuum with delusions in individuals suffering from psychosis (Freeman, 2006; Linscott and van Os, 2013; Zavos et al., 2014), and alterations in the self-related processes have been demonstrated for both unfounded beliefs in the healthy (Fenigstein and Vanable, 1992) and delusions in psychotic individuals (Smári et al., 1994). This suggests that the tendency toward unfounded beliefs represents a continuously distributed phenotype that in its extreme form can lead to significant distress and social isolation. "
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    ABSTRACT: Unfounded convictions involving beliefs in the paranormal, grandiosity ideas or suspicious thoughts are endorsed at varying degrees among the general population. Here, we investigated the neurobiopsychological basis of the observed inter-individual variability in the propensity toward unfounded beliefs. One hundred two healthy individuals were genotyped for four polymorphisms in the COMT gene (rs6269, rs4633, rs4818, and rs4680, also known as val (158) met) that define common functional haplotypes with substantial impact on synaptic dopamine degradation, completed a questionnaire measuring unfounded beliefs, and took part in a behavioral experiment assessing perceptual inference. We found that greater dopamine availability was associated with a stronger propensity toward unfounded beliefs, and that this effect was statistically mediated by an enhanced influence of expectations on perceptual inference. Our results indicate that genetic differences in dopaminergic neurotransmission account for inter-individual differences in perceptual inference linked to the formation and maintenance of unfounded beliefs. Thus, dopamine might be critically involved in the processes underlying one's interpretation of the relationship between the self and the world.
    Full-text · Article · Sep 2015 · Frontiers in Human Neuroscience
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    • "132). Echoing this, Freeman (2006) suggested that delusions are commonly found in the general (non-clinical) population , among individuals without psychosis. Approximately 1–3% of the non-clinical population were estimated to have delusions of a level of severity comparable to clinical cases of psychosis, with a further 5–6% having delusions of lesser severity that were nonetheless associated with a range of social and emotional difficulties. "
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    ABSTRACT: Evidence suggests that consideration of personality disorder (PD) severity, incorporating both externalising and internalising features of PD, might help to clarify the PD – violence relationship; moreover, that separate developmental pathways might link externalising and internalising personality pathology with criminal violence. This study of 96 forensic patients with confirmed PD and a history of violent offending addressed the question of whether delusional ideation, measured by the Peters Delusions Inventory, might play a significant role in the link between severe PD and criminal violence. Severe PD, defined by summing scores across DSM-IV PD criteria, was significantly associated with delusional thinking, with violence, and with high levels of both externalising and internalising personality features. Delusional thinking was associated with violence via internalising but not externalising PD features, suggesting that the link between severe PD and violence may be partly mediated by delusional thinking.
    Full-text · Article · Feb 2015 · Journal of Forensic Psychiatry and Psychology
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