The psychometric properties of the Peters et al. delusions inventory (PDI) in Taiwan: reliability, validity, and utility

Evaluation of reliability and validity of the Persian version of Peters et al. delusions inventory (PDI-40) in iranian non-clinical and clinical samples

BACKGROUND

Some individuals may manifest psychotic symptoms that do not fulfill the requisite clinical criteria for a formal diagnosis of psychosis. The assessment of susceptibility to delusions, encompassing both clinical and non-clinical cohorts, frequently makes use of the Peters et al. Delusions Inventory (PDI-40). This study aimed to evaluate the reliability and validity of the Persian version of Peters et al. Delusions Inventory (PDI-40) in Iranian non-clinical and clinical samples.

METHODS

The present study employed a cross-sectional, correlational design in 2020. A total of 1402 Iranian participants were recruited for the study, which consisted of three distinct stages. The first stage involved an Exploratory Factor Analysis (EFA) conducted on a non-clinical sample of 512 participants. The second stage comprising different non-clinical sample 764 participants to perform a Confirmatory Factor Analysis (CFA). In the third stage, a clinical sample of 126 psychotic patients was compared to a non-clinical sample. All participants completed the PDI-40, the Community Assessment of Psychotic Experiences (CAPE-42), and the Depression, Anxiety, and Stress Scale (DASS-21). The internal structure of PDI-40 was examined through the analysis of its factor structure using LISREL 8.8.

RESULTS

The EFA analysis unveiled nine components within Persian version of PDI-40. The CFA analysis demonstrated an excellent fit of the nine-factor structure of Persian PDI-40 to the data. The total score exhibited high internal reliability, as indicated by Cronbach's alpha coefficient of 0.92. Moreover, Persian PDI-40 exhibited satisfactory evidence of convergent validity, as significant correlations were observed between dimensions of PDI-40 and subscales of CAPE-42 and DASS-21. Lastly, findings indicated that psychotic participants scored higher than non-clinical participants in all components of the PDI-40(p < 0.05).

CONCLUSION

Persian version of the PDI-40 demonstrates strong reliability and validity for assessing delusion proneness in both non-clinical and clinical samples in Iran. The observed distinctions between psychotic and non-clinical participants underscore its potential as a valuable tool for discerning delusion proneness in diverse contexts.

Emotion regulation and delusion-proneness relate to empathetic tendencies in a transdiagnostic sample

Empathetic tendencies (i.e., perspective taking and empathic concern) are a key factor in interpersonal relationships, which may be impacted by emotion regulation (i.e., reappraisal and suppression) and mental health symptoms, such as psychotic-like experiences. However, it is unclear if certain psychotic-like experiences, such as delusion-proneness, are still associated with reduced empathetic tendencies after accounting for emotion regulation style and dimensions of psychopathology that are often comorbid. In the current study, linear models tested these associations in a transdiagnostic community sample (N = 128), using the Interpersonal Reactivity Index (IRI), Emotion Regulation Questionnaire, and the Peter's Delusion Inventory. Results indicated that perspective taking was positively associated with reappraisal and negatively associated with delusion-proneness, after controlling for age, sex, race, intelligence, and symptoms of anxiety and depression. A significant change in R 2 supported the addition of delusion-proneness in this model. Specificity analyses demonstrated perspective taking was also negatively associated with suppression, but this relationship did not remain after accounting for the effects of reappraisal and delusion-proneness. Additional specificity analyses found no association between empathic concern and reappraisal or delusion-proneness but replicated previous findings that empathic concern was negatively associated with suppression. Taken together, delusion-proneness accounts for unique variance in perspective taking, which can inform future experimental research and may have important implications for psychosocial interventions.

Impairment in acquisition of conditioned fear in schizophrenia

Individuals with schizophrenia show impairments in associative learning. One well-studied, quantifiable form of associative learning is Pavlovian fear conditioning. However, to date, studies of fear conditioning in schizophrenia have been inconclusive, possibly because they lacked sufficient power. To address this issue, we pooled data from four independent fear conditioning studies that included a total of 77 individuals with schizophrenia and 74 control subjects. Skin conductance responses (SCRs) to stimuli that were paired (the CS + ) or not paired (CS-) with an aversive, unconditioned stimulus were measured, and the success of acquisition of differential conditioning (the magnitude of CS + vs. CS- SCRs) and responses to CS + and CS- separately were assessed. We found that acquisition of differential conditioned fear responses was significantly lower in individuals with schizophrenia than in healthy controls (Cohen's d = 0.53). This effect was primarily related to a significantly higher response to the CS- stimulus in the schizophrenia compared to the control group. Moreover, the magnitude of this response to the CS- in the schizophrenia group was correlated with the severity of delusional ideation (p = 0.006). Other symptoms or antipsychotic dose were not associated with fear conditioning measures. In conclusion, individuals with schizophrenia who endorse delusional beliefs may be over-responsive to neutral stimuli during fear conditioning. This finding is consistent with prior models of abnormal associative learning in psychosis.

Invariance of factor structure of the 21-item Peters et al. Delusions Inventory (PDI-21) over time and across samples

The present study aimed to explore the latent structure of the 21-item Peters et al. Delusions Inventory (PDI-21) and to test the invariance of its factor structure over time and across samples. The PDI-21 was administered in two samples; one consisting of 1655 undergraduate students investigated in three waves, each separated by six months; and another consisting of 196 outpatients with schizophrenia. Exploratory factor analysis was performed to explore the internal structure of the PDI-21 based on number of beliefs and the grand total scores separately. The number of factors was determined by optimal implementation of parallel analysis. Confirmatory factor analysis, cross-time and cross-sample invariance analyses were carried out with Mplus. Both exploratory factor analysis and the optimal implementation of parallel analysis (based on the number of beliefs and the total score of the PDI-21) suggested a one-factor solution. However, the confirmatory factor analysis revealed a single-dimension structure based on number of beliefs only, which exhibited goodness of fit and stability across time and samples. Our study demonstrated a single-dimension structure of the PDI-21, which can be widely used in screening the number of delusional ideations both in clinical and non-clinical populations.

Jumping to conclusions style along the continuum of delusions: delusion-prone individuals are not hastier in decision making than healthy individuals

Literature comparing 'jumping to conclusions' (JTC) between patients and healthy controls has demonstrated the importance of the reasoning bias in the development of delusions. When groups that vary along the entire delusional continuum are included, the relationship between JTC and delusionality is less clear. This study compared JTC and delusional dimensions between 28 patients with delusions, 35 delusion-prone individuals and 32 non-delusion-prone individuals. Delusion proneness was defined by an established threshold based on the Peters et al. Delusions Inventory. Two versions of the beads task (85:15 and 60:40) were used to measure JTC. As hypothesized, patients manifested hastier data gathering than the two non-clinical groups on both beads tasks. However, delusion-prone individuals did not manifest a hastier decision making style than non-delusion prone individuals. Instead, non-delusion-prone participants showed more JTC bias than delusion-prone individuals on the easier beads task. There was no evidence for a dose-response relationship between JTC and delusional dimensions, with correlations between JTC and PDI scores found in the non-delusion-prone group only. The present finding confirms the link between an extreme JTC bias and the presence of clinical delusions, and argues against a linear relationship between JTC and delusionality along the symptomatic continuum.

Relationships of perceived public stigma of mental illness and psychosis-like experiences in a non-clinical population sample

PURPOSE

Studies on the association between psychopathology, perceived public stigma, and labeling in mental illness have focused primarily on severe but rare mental disorders, especially schizophrenia, or other clinically defined psychotic disorders. Although evidence is mounting that psychosis-like experiences show high prevalence in the general population and lead to an increased risk of psychotic disorders, little is known about how psychosis-like experiences independently affect perceived public stigma in the non-clinical population. The aim of the present study was to examine the relationship between psychosis-like experiences and perceived public stigma in a non-clinical sample.

METHODS

For this cross-sectional study, we recruited 524 individuals (239 male, 285 female) who had no lifetime history of psychiatric disorder. Participants completed questionnaires that asked for sociodemographic and clinical information, a measure of perceived public stigma (Perceived Psychiatric Stigma Scale [PPSS]), and two measures of psychosis-like experiences (Peters et al. Delusions Inventory [PDI]; Cardiff Anomalous Perceptions Scale [CAPS]).

RESULTS

Of the sociodemographic characteristics analyzed in this study-gender, age, education level, marital status, and religion-only age simultaneously influenced PPSS, PDI, and CAPS scores. As hypothesized, perceived public stigma was positively correlated with measures of psychosis-like experiences, even after controlling for age. Furthermore, the perceived stigma was more strongly associated with delusion proneness than with anomalous perceptual experiences.

CONCLUSION

The association between psychopathology and perceived public stigma appears to extend beyond clinically defined psychosis to more common psychosis-like experiences in a sample drawn from the general Han Chinese population.

The neurobiology of schizotypy: fronto-striatal prediction error signal correlates with delusion-like beliefs in healthy people

Healthy people sometimes report experiences and beliefs that are strikingly similar to the symptoms of psychosis in their bizarreness and the apparent lack of evidence supporting them. An important question is whether this represents merely a superficial resemblance or whether there is a genuine and deep similarity indicating, as some have suggested, a continuum between odd but healthy beliefs and the symptoms of psychotic illness. We sought to shed light on this question by determining whether the neural marker for prediction error - previously shown to be altered in early psychosis--is comparably altered in healthy individuals reporting schizotypal experiences and beliefs. We showed that non-clinical schizotypal experiences were significantly correlated with aberrant frontal and striatal prediction error signal. This correlation related to the distress associated with the beliefs. Given our previous observations that patients with first episode psychosis show altered neural responses to prediction error and that this alteration, in turn, relates to the severity of their delusional ideation, our results provide novel evidence in support of the view that schizotypy relates to psychosis at more than just a superficial descriptive level. However, the picture is a complex one in which the experiences, though associated with altered striatal responding, may provoke distress but may nonetheless be explained away, while an additional alteration in frontal cortical responding may allow the beliefs to become more delusion-like: intrusive and distressing.