Biomedical subjects

E R Peters

Publications and source records attributed to E R Peters.

18 recordsLinked to original sources

PubMed2005

Disease, deficit or denial? Models of poor insight in psychosis.

OBJECTIVE: To examine the evidence for the three kinds of aetiological model that dominate the current literature on poor insight in psychosis: clinical models, the neuropsychological model, and the psychological denial model. METHOD: Studies pertaining to one or more of these aetiological models were identified, reviewed and critically evaluated. RESULTS: There is little support for clinical models, partly because they lack testable hypotheses. Several studies reveal a positive relationship between insight and executive function, which may be related to frontal lobe dysfunction. However, the extent to which this relationship is specific and independent of general cognitive impairment remains unclear. There is tentative evidence to support the psychological denial model. Recent data combining the latter two approaches suggest that multiple factors contribute to poor insight. CONCLUSION: Integration of different aetiological models is necessary for a fuller understanding of insight in psychosis. Future research should assess multiple aetiological mechanisms in single investigations.

Attitude to Health↗

PubMed2003

A quantitative genetic analysis of schizotypal personality traits.

BACKGROUND: Previous twin studies investigating the heritability of schizotypy have often had limited power and have failed to measure the disorganization/social anxiety component. METHOD: Seven hundred and thirty-three female twin pairs, drawn from the Institute of Psychiatry Volunteer Twin Register, completed the Oxford-Liverpool Inventory of Feelings and Experiences and the Peters et al. Delusions Inventory. Structural equation modelling was carried out on scores for MZ and DZ twin pairs. RESULTS: The best fitting models for all scales comprised additive genetic and unique environmental effects. Heritability was estimated at approximately 50% for most scales, although it was lower at 37% for the PDI scale. Multivariate structural equation model fitting revealed a best-fitting model in which additive genetic and unique environmental influences act through a single common pathway for Cognitive Disorganization, Unusual Experiences and the PDI, and through a separate common pathway for Cognitive Disorganization and Introvertive Anhedonia. CONCLUSIONS: The various components of schizotypy are moderately heritable. Multivariate model fitting indicates that at least two latent factor structures are required to account for the covariation between the various components of schizotypy. The positive and negative components of schizotypy are relatively genetically independent, although each in turn may be related to Cognitive Disorganization.

Adolescent↗

PubMed2001

The incidence of schizotypy among cannabis and alcohol users.

Schizotypy research has revealed associations between positive schizotypal symptomatology and substance use but has not related substance use to important schizotypal traits such as anhedonia. Users and nonusers of cannabis and alcohol completed the Oxford-Liverpool Inventory of Feelings and Experiences, the Peters Delusion Inventory, and the Hospital Anxiety and Depression Scale. Cannabis users scored significantly higher on Unusual Experiences, a scale measuring positive schizotypal symptomatology. Both cannabis and alcohol usage were associated with significantly lower scores on Introvertive Anhedonia, which represents negative symptomatology. Delusional ideation and delusional conviction were significantly higher in cannabis users, but for delusional conviction this was only true for users who also drank alcohol. Neither anxiety or depression scores were higher in cannabis users, but delusional ideation correlated with both anxiety and depression, thus providing mixed support for the idea of the "happy schizotype." Overall, these results suggest that cannabis and alcohol usage is related to different dimensions of psychosis-proneness that broadly parallel the relationship between substance use and positive and negative schizophrenic symptoms, thus supporting the continuity view of psychosis and the multidimensionality of psychosis-proneness.

Adolescent↗

PubMed1999

Ethnicity, class and schizotypy.

BACKGROUND: This study investigated whether, similarly to schizophrenia, there is an increased rate of schizotypy among African-Caribbeans in the general population compared with white people in the UK. Since social adversity has been associated with schizophrenia in a number of studies, social class as well as ethnicity was explored. In addition, any differences between the groups in neurotic pathology were investigated. METHODS: Four groups of 12 participants (African-Caribbean, working-class; African-Caribbean, middle-class; white, middle-class; white, working-class) were interviewed using The Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE), The Peters et al. Delusions Inventory (PDI), The Delusions-Symptoms-State-Inventory (DSSI) and The Hospital Anxiety and Depression Scale (HADS). RESULTS: As predicted, African-Caribbean participants scored higher than the white participants on the PDI. There was a significant interaction between ethnicity and class, with African-Caribbean, working-class participants scoring higher than the other three groups on the PDI as well as on the DSSI. There was an unexpected effect of class, with the middle-classes scoring higher than the working-classes on the O-LIFE category of 'impulsive non-conformity'. CONCLUSIONS: These findings suggest that it is delusional ideation specifically, rather than general schizotypy, that is higher in the African-Caribbean population. However, whether this is a reflection of their social reality or their psychosis proneness is unclear. Furthermore, the results suggest that class is a significant factor in the expression of delusional ideation in African-Caribbeans.

Adult↗

PubMed1999

Measurement of delusional ideation in the normal population: introducing the PDI (Peters et al. Delusions Inventory).

The Peters et al. Delusions Inventory (PDI) was designed to measure delusional ideation in the normal population, using the Present State Examination as a template. The multidimensionality of delusions was incorporated by assessing measures of distress, preoccupation, and conviction. Individual items were endorsed by one in four adults on average. No sex differences were found, and an inverse relationship with age was obtained. Good internal consistency was found, and its concurrent validity was confirmed by the percentages of common variance with three scales measuring schizotypy, magical ideation, and delusions. PDI scores up to 1 year later remained consistent, establishing its test-retest reliability. Psychotic inpatients had significantly higher scores, establishing its criterion validity. The ranges of scores between the normal and deluded groups overlapped considerably, consistent with the continuity view of psychosis. The two samples were differentiated by their ratings on the distress, preoccupation, and conviction scales, confirming the necessity for a multidimensional analysis of delusional thinking. Possible avenues of research using this scale and its clinical utility are highlighted.

Adult↗

PubMed1998

Reasoning biases in delusion-prone individuals.

OBJECTIVES: The objective was to test whether individuals high in delusional ideation exhibit a reasoning bias on tasks involving hypothesis testing and probability judgments. On the basis of previous findings (e.g. Garety, Hemsley & Wessely, 1991), it was predicted that individuals high in delusional ideation would exhibit a 'jump-to-conclusions' style of reasoning and would be less sensitive to the effects of random variation, in comparison to individuals low in delusional ideation. DESIGN: A non-randomized matched groups design was employed enabling the performance of the delusion prone individuals to be compared to that of a control group. METHOD: Forty individuals, selected from the normal population, were divided into groups high and low in delusional ideation, according to their scores on the Peters et al. Delusions Inventory (Peters, Day & Garety, 1996), and were compared on two tasks involving probability judgment and two tasks involving hypothesis testing. RESULTS: Although no significant differences were found on tasks involving hypothesis testing and the aggregation of probabilistic information, it was found that individuals high in delusional ideation had a 'jump-to-conclusions' style of data gathering and were less sensitive to the effects of random variation, in comparison to individuals low in delusional ideation. CONCLUSIONS: In conclusion, although individuals high in delusional ideation were not found to have a general reasoning bias, some evidence of a more specific bias was found. It is thought that these aberrations may play some role in delusion formation in schizophrenia and paranoia.

Adult↗

PubMed1994

'Cognitive inhibition' and positive symptomatology in schizotypy.

The negative priming paradigm (Tipper, 1985) was used to investigate the relationship between 'cognitive inhibition' and symptoms of reality distortion in schizotypy, after previous findings that the negative priming effect is reduced in both acute schizophrenics and high schizotypes (Beech, Powell, McWilliam & Claridge, 1989; Beech, Baylis, Smithson & Claridge, 1989). Following Frith's (1979) model, which suggests that the positive symptoms of schizophrenia are due to a failure of the inhibitory processes which normally limit the contents of consciousness, it was predicted that negative priming would be inversely correlated with levels of positive symptomatology, as measured by the CSTQ (Bentall, Claridge & Slade, 1989). The results supported the hypothesis, which confirms the usefulness of a symptom-oriented approach as well as providing some validation for the concept of schizotypy. It was concluded that high schizotypes, similarly to acute schizophrenics, show a reduction in 'cognitive inhibition', as was predicted by Frith's (1979) model.

Adult↗

PubMed1973