Delusions in the nonclinical population.
ABSTRACT 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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ABSTRACT: Background: Patients with schizophrenia show overconfidence in memory and social cognition errors. The present investigation examined whether this cognitive distortion also manifests in perceptual tasks. Methods: A total of 55 individuals with schizophrenia, 58 with obsessive–compulsive disorder (OCD) as well as 45 non-clinical controls were presented 24 blurry black and white pictures, half of which contained a hidden object; the other half contained (" snowy ") visual noise. Participants had to judge whether the pictures depicted an object or not and how confident they were in this judgment. Results: Participants with schizophrenia showed overconfidence in errors and an enhanced knowledge corruption index (i.e. rate of high-confident errors on all high-confident responses) relative to both control groups. In contrast, accuracy scores did not differ between clinical groups. Metacognitive parameters were correlated with self-rated levels of current paranoia. Discussion: To the best of our knowledge, this is the first study to demonstrate overconfidence in errors among individuals with psychosis using a visual perception task. Speaking to the specificity of this abnormality for schizophrenia and its pathogenetic relevance, overconfidence in errors and knowledge corruption were elevated in patients with schizophrenia relative to both control groups and were correlated with paranoia.
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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.Journal of Behavior Therapy and Experimental Psychiatry 12/2015; 48. DOI:10.1016/j.jbtep.2015.02.011 · 2.23 Impact Factor
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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.Journal of Forensic Psychiatry and Psychology 02/2015; DOI:10.1080/14789949.2015.1017594 · 0.88 Impact Factor