Trends in Cognitive Sciences
Explaining delusions: a cognitive perspective
Introduction
Delusions are a key clinical manifestation of psychosis and have particular significance for the diagnosis of schizophrenia. Although common in several psychiatric conditions, they also occur in a diverse range of other disorders (including brain injury, intoxication and somatic illness). Delusions are significant precisely because they make sense for the believer and are held to be evidentially true, often making them resistant to change.
Although an important element of psychiatric diagnosis, delusions have yet to be adequately defined (see existing diagnostic criteria; Box 1). Despite this operational ambiguity, the concept of a ‘delusion’ as a core psychopathological feature, indicative of a substantial break with reality (where patients might claim to be under the influence of non-existent or impossible machines or persecuted by invisible malign agents, to name but two examples; see Table 1) continues to have widespread clinical acceptance.
Notwithstanding issues of definition, the last decade has witnessed a particular intensification of research on delusions, with cognitive neuroscience-based approaches providing increasingly useful and testable frameworks from which to construct a better understanding of how cognitive and neural systems are involved [1]. These in turn have informed cognitive behavioural therapy, which has been shown to be an effective therapeutic approach [2].
A number of models of delusion formation have arisen from these research efforts, although little attempt has been made to bring together approaches from disparate traditions to assess critically their assumptions and contributions to a wider understanding of the phenomena. This review evaluates these models and draws attention to ambiguities in the empirical evidence, as well as highlighting areas needing further theoretical development.
Section snippets
Evidence for cognitive dysfunction and bias in delusions
Considerable data have been gathered over the past decade that suggest the presence of cognitive biases in people with delusions or those prone to delusional thinking. As many of the broader models of delusion formation draw on the same evidence (despite differing interpretations) recent work in this area is briefly reviewed to provide a context for the later discussion of the competing theoretical approaches.
Cognitive models of delusion formation
In clinical psychiatry, and in much of the empirical evidence reviewed above, delusions are traditionally considered to be ‘pathological beliefs’, although existing cognitive approaches differ in their willingness to explain delusions within a model of impairment to normal belief formation. Accordingly, this review examines cognitive approaches to delusions under two broad headings: (i) ‘belief-positive’ models, that frame themselves within (and often contribute towards) an explicit model of
Continuum approaches to delusions
The continuum approach to psychosis draws inspiration from epidemiological approaches to look for predictors and correlates of delusional ideation and/or frank delusions within the wider population. Although not a model of delusion formation per se (and hence compatible with both belief-positive and belief-negative models) the continuum approach suggests that delusions are not qualitatively different from normal beliefs, but simply represent a more extreme end of the population spectrum or
Concluding remarks
This review highlights a striking neglected issue: current models that make no distinction between beliefs resulting in pragmatic distress and impairment, and those that are simply impossible or anomalous, are unable to distinguish between beliefs that are clinically significant, and those that may be unusual or ‘magical’, but otherwise benign. Hence, an adequate theory should also explain the ‘pragmatic pathology’ of delusions. Cognitive theories that achieve this will be able both to address
References (69)
The effect of cognitive behavioral treatment on the positive symptoms of schizophrenia spectrum disorders: a meta-analysis
Schizophr. Res.
(2005)- et al.
Cognitive functioning in delusions: A longitudinal analysis
Behav. Res. Ther.
(2006) Persecutory delusions: a review and theoretical integration
Clin. Psychol. Rev.
(2001)Paranoia, persecutory delusions and attributional biases
Psychiatry Res.
(2005)Persecutory beliefs, attributions and theory of mind: comparison of patients with paranoid delusions, Asperger's syndrome and healthy controls
Schizophr. Res.
(2004)- et al.
The relevance of irrelevance to schizophrenia
Neurosci. Biobehav. Rev.
(2005) Source monitoring impairments in schizophrenia: characterisation and associations with positive and negative symptomatology
Psychiatry Res.
(2002)Investigation of metamemory dysfunctions in first-episode schizophrenia
Schizophr. Res.
(2006)A positive emotional bias in confabulatory false beliefs about place
Brain Cogn.
(2004)Anosognosia in parietal lobe syndrome
Conscious. Cogn.
(1995)
Delusional misidentification
Psychiatr. Clin. North Am.
The anatomy of anosognosia for hemiplegia: a meta-analysis
Cortex
Hemispheric lateralization patterns and psychotic experiences in healthy subjects
Psychiatry Res.
Deluding the motor system
Conscious. Cogn.
Abnormalities in the awareness of action
Trends Cogn. Sci.
The self in action: Lessons from delusions of control
Conscious. Cogn.
Disorders of agency in schizophrenia correlate with an inability to compensate for the sensory consequences of actions
Curr. Biol.
The continuity of psychotic experiences in the general population
Clin. Psychol. Rev.
Subtle fluctuations in psychotic phenomena as functional States of abnormal dopamine reactivity in individuals at risk
Biol. Psychiatry
The cognitive neuropsychiatry of delusions: from psychopathology to neuropsychology and back again
Psychol. Med.
Delusions: Investigations into the Psychology of Delusional Reasoning
Jumping to conclusions in delusional and non-delusional schizophrenic patients
Br. J. Clin. Psychol.
Data gathering: biased in psychosis?
Schizophr. Bull.
Reasoning, emotions, and delusional conviction in psychosis
J. Abnorm. Psychol.
Need for closure and jumping-to-conclusions in delusion-prone individuals
J. Nerv. Ment. Dis.
Cognitive approaches to delusions: a critical review of theories and evidence
Br. J. Clin. Psychol.
Theory of mind, causal attribution and paranoia in Asperger syndrome
Autism
Externalizing and personalizing biases in persecutory delusions: The relationship with poor insight and theory-of-mind
Behav. Res. Ther.
Confidence in errors as a possible basis for delusions in schizophrenia
J. Nerv. Ment. Dis.
‘Theory of mind’ in schizophrenia: a review of the literature
Schizophr. Bull.
Schizophrenia and theory of mind
Psychol. Med.
No evidence for impaired ‘theory of mind’ in unaffected first-degree relatives of schizophrenia patients
Acta Psychiatr. Scand.
The cognitive neuropsychology of delusions
Monothematic delusions: Towards a two-factor account
Philos. Psychiatry Psychol.
Cited by (163)
Efficacy of Metacognitive Training in a Chilean Sample of People with Schizophrenia
2022, Revista Colombiana de PsiquiatriaRemote group therapies for cognitive health in schizophrenia-spectrum disorders: Feasible, acceptable, engaging
2022, Schizophrenia Research: CognitionPeople with schizophrenia use less information to interpret ambiguous social situations
2022, Journal of Behavior Therapy and Experimental Psychiatry