Correlates of delusion-like experiences in a non-psychotic community sample

Robotically-induced auditory-verbal hallucinations: combining self-monitoring and strong perceptual priors

BACKGROUND

Inducing hallucinations under controlled experimental conditions in non-hallucinating individuals represents a novel research avenue oriented toward understanding complex hallucinatory phenomena, avoiding confounds observed in patients. Auditory-verbal hallucinations (AVH) are one of the most common and distressing psychotic symptoms, whose etiology remains largely unknown. Two prominent accounts portray AVH either as a deficit in auditory-verbal self-monitoring, or as a result of overly strong perceptual priors.

METHODS

In order to test both theoretical models and evaluate their potential integration, we developed a robotic procedure able to induce self-monitoring perturbations (consisting of sensorimotor conflicts between poking movements and corresponding tactile feedback) and a perceptual prior associated with otherness sensations (i.e. feeling the presence of a non-existing another person).

RESULTS

Here, in two independent studies, we show that this robotic procedure led to AVH-like phenomena in healthy individuals, quantified as an increase in false alarm rate in a voice detection task. Robotically-induced AVH-like sensations were further associated with delusional ideation and to both AVH accounts. Specifically, a condition with stronger sensorimotor conflicts induced more AVH-like sensations (self-monitoring), while, in the otherness-related experimental condition, there were more AVH-like sensations when participants were detecting other-voice stimuli, compared to detecting self-voice stimuli (strong-priors).

CONCLUSIONS

By demonstrating an experimental procedure able to induce AVH-like sensations in non-hallucinating individuals, we shed new light on AVH phenomenology, thereby integrating self-monitoring and strong-priors accounts.

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.

Psychotic-like experiences in general population: Psychiatric comorbidity and impact on quality of life across lifespan

BACKGROUND AND HYPOTHESIS

In this study, we aimed to determine the prevalence of Psychotics-Like Experiences according to age group and their association with psychiatric disorders through these different age-group, as well as their impact on quality of life.

STUDY DESIGN

Using data from the second wave of the NESARC, a large general population study, we considered 6 mutually exclusive groups according to the age at the interview: 20-29 years; 30-39 years; 40-49 years; 50-59 years; 60-69 years; 70+ years. We determined the frequency of PLEs defined as positive, negative, depressive, mania and disorganization symptoms with reference to the PANSS, and the association between the presence of PLEs in the previous year and the presence of lifetime psychiatric disorders and quality of life across different age groups.

STUDY RESULTS

The prevalence of PLEs decreased across age from a 34.7 % in the 20-29 years age group, to 19.7 % in the 70+ years age group. Across all age groups, individuals who reported PLEs in the previous year had higher risk of having any psychiatric disorder, (i.e any mood disorder, any anxiety disorder any substance abuse and any personality disorder) compared to individuals not reporting PLEs. All dimensions of quality of life on the SF12 scale were negatively associated with the presence of a PLE regardless of age group.

CONCLUSION

We found that the frequency of PLEs decreased with age and that the presence of PLE is associated with psychiatric disorders and with impaired quality of life in all age groups.

Mapping psychotic-like experiences: Results from an online survey

Suggestions have been made that psychotic-like experiences (PLEs), such as hallucinatory and delusional experiences, exist on a continuum from healthy individuals to patients with a diagnosis of schizophrenia. We used the screening questions of the Questionnaire for Psychotic Experiences (QPE), an interview that captures the presence and phenomenology of various psychotic experiences separately, to assess PLEs in Norway. Based on data from an online survey in a sample of more than 1,400 participants, we demonstrated that the QPE screening questions show satisfactory psychometric properties. Participants with mental disorders reported more frequent lifetime and current hallucinatory experiences than participants without mental disorders. Childhood experiences were rather low and ranged from 0.7% to 5.2%. We further replicated findings that young age, illegal drug use, lower level of education, and having parents with a mental disorder are associated with higher endorsement rates of PLEs. Finally, a binomial regression revealed that the mere presence of PLEs does not discriminate between individuals with and without a mental disorder. Taken together, the findings of the present study support existing models that both hallucinations and delusions exist on a structural and phenomenological continuum. Moreover, we demonstrated that the QPE screening questions can be used by themselves as a complementary tool to the full QPE interview.

Form and content of attenuated psychotic symptoms in psychometrically assessed positive and negative schizotypy

AIM

Greater attention is being paid to early detection and identification of individuals who are at high risk of developing psychosis. One area of interest is the particular content types of psychotic-like experiences (PLEs), which can be thought of as attenuated, non-clinical positive symptoms (eg, feeling perplexed by reality). Previous research has examined content of PLEs in clinical high-risk samples. The current study aimed to build upon these findings by analysing content in a psychometrically determined high-risk sample.

METHODS

One hundred fifty-three undergraduates with scores greater than 1.96 SDs above the mean on a measure of schizotypy symptoms participated in a semi-structured interview for the assessment of prodromal syndromes. Each interview was transcribed verbatim and content of PLEs was rated according to the Content of Attenuated Positive Symptoms scale.

RESULTS

Frequencies of content items in the psychometric high-risk sample were similar to those found in a clinical high-risk sample. Multiple regression analyses revealed that certain content items were more predictive of decreased global functioning and increased positive symptom severity.

CONCLUSIONS

Content items that were associated with worse outcomes may be cause for greater concern if endorsed by individuals presenting for treatment. Future research should examine content of PLEs in a longitudinal design to determine whether particular items could predict subsequent conversion to a schizophrenia-spectrum disorder.

Increased amygdala-visual cortex connectivity in youth with persecutory ideation

BACKGROUND

Subclinical delusional ideas, including persecutory beliefs, in otherwise healthy individuals are heritable symptoms associated with increased risk for psychotic illness, possibly representing an expression of one end of a continuum of psychosis severity. The identification of variation in brain function associated with these symptoms may provide insights about the neurobiology of delusions in clinical psychosis.

METHODS

A resting-state functional magnetic resonance imaging scan was collected from 131 young adults with a wide range of severity of subclinical delusional beliefs, including persecutory ideas. Because of evidence for a key role of the amygdala in fear and paranoia, resting-state functional connectivity of the amygdala was measured.

RESULTS

Connectivity between the amygdala and early visual cortical areas, including striate cortex (V1), was found to be significantly greater in participants with high (n = 43) v. low (n = 44) numbers of delusional beliefs, particularly in those who showed persistence of those beliefs. Similarly, across the full sample, the number of and distress associated with delusional beliefs were positively correlated with the strength of amygdala-visual cortex connectivity. Moreover, further analyses revealed that these effects were driven by those who endorsed persecutory beliefs.

CONCLUSIONS

These findings are consistent with the hypothesis that aberrant assignments of threat to sensory stimuli may lead to the downstream development of delusional ideas. Taken together with prior findings of disrupted sensory-limbic coupling in psychosis, these results suggest that altered amygdala-visual cortex connectivity could represent a marker of psychosis-related pathophysiology across a continuum of symptom severity.

Prevalence and correlates of psychotic-like experiences in the general population

BACKGROUND

To what extent Psychotic Like Experiences (PLEs) are associated with nonpsychotic psychiatric disorders and whether the number of PLEs is associated with higher rates of psychiatric disorders remains unclear.

METHODS

The sample was composed of 34,653 civilian participants, aged 18 years and older from wave 2 National Epidemiologic Survey on Alcohol and Related Conditions (NESARC). This was a representative sample of the non-institutionalized U.S.

POPULATION

Twenty-two PLEs were assessed. Lifetime prevalence of psychiatric disorders (any mood, anxiety, substance use and personality disorders, PTSD, ADHD, and suicide attempts) according to the number of PLEs were calculated.

RESULTS

Almost a third (26.69%) of respondents reported experiencing at least one type of PLEs. There was a gradual association between the number of PLEs and the presence of a nonpsychotic psychiatric disorder (ranging from 5.68%in participants with no PLEs up to 99.53% in those with five or more PLEs). This association with PLE was significant for each of the 25 psychiatric disorders examined regardless of the number of PLEs. Lifetime prevalence of PLEs were significantly higher among the younger respondents, women, non-married, unemployed, high educational level and those with low family income.

CONCLUSION

There is a gradual increase in the magnitude of the association of the numbers of PLEs for each of the 25 nonpsychotic psychiatric disorders examined. Having at least one PLE is strongly associated with the presence of a psychiatric disorder.

Family history of psychosis and outcome of people with schizophrenia in rural China: 14-year follow-up study

OBJECTIVE

This study examined the differences in 14-year outcomes of persons with schizophrenia with and without family history of psychosis in a rural community in China.

METHODS

All participants with schizophrenia (n=510) aged 15 years and older were identified in a 1994 epidemiological investigation of 123,572 people and followed up in 2004 and 2008 in Xinjin County, Chengdu, China.

RESULTS

Individuals with positive family history of schizophrenia had significantly younger age of first onset than those with negative family history of schizophrenia in 1994 and 2004. Compared with individuals with negative family history of schizophrenia, those with positive family history of schizophrenia had significantly higher rate of homelessness and lower rate of death due to other reasons in 10-year (2004) and 14-year follow-up (2008). There were no significantly differences of mean scores on PANSS, SDSS and GAF in 2008 between positive and negative family history groups.

CONCLUSIONS

The positive family history of schizophrenia is strongly related to younger age of onset, and may predict a poorer long-term outcome (e.g., higher rate of homelessness) in persons with schizophrenia in the rural community. The findings have implications for further studies on specific family-related mechanisms on clinical treatment and rehabilitation, as well as for planning and delivering of community-based mental health services.

Face Processing Measures of Social Cognition: A Dimensional Approach to Developmental Psychopathology

BACKGROUND

Social cognition impairments in neurodevelopmental disorders impact functioning. Face processing is the most extensively studied aspect of social cognition, commonly indexing this construct in neuropsychiatric disorders compared with typically developing youths. Applying social cognition measures as a Research Domain Criteria concept in the clinical arena requires establishing cutoffs for intervention and identifying vulnerability for psychopathology across disorders. This can be accomplished by comparing extreme performers across multiple clinical symptom features.

METHODS

The Philadelphia Neurodevelopmental Cohort (N = 9498), a community sample of youths (8-21 years old), was assessed with a structured interview (Kiddie Schedule for Affective Disorders and Schizophrenia). The Penn Computerized Neurocognitive Battery was administered measuring accuracy and response time on Executive, Episodic Memory, Complex Cognition, and Social Cognition domains. We parsed participants by performance on social cognition into tertiles and examined their neurocognitive and clinical profiles.

RESULTS

The top social cognition group outperformed the bottom group in face memory and complex reasoning. Concerning symptoms, the top performing group did not differ from the middle group, but the bottom performing group had higher externalizing and psychosis symptoms. There were sex differences in social cognition and symptom profiles but no sex × performance or sex × diagnosis × domain interactions.

CONCLUSIONS

Social cognition is supported by strong face memory and complex reasoning skills. Poor performance portends more severe externalizing and psychosis symptoms. That average performance is sufficient for normative symptomatology suggests that interventions aimed at ameliorating social cognition deficits, as measured here, could be effective in normalizing level of symptoms.

Attachment in psychosis: A latent profile analysis of attachment styles and association with symptoms in a large psychosis cohort

Attachment has been identified as one of various possible mechanisms involved in understanding models of psychosis, but measures that reliably and validly assess attachment styles in psychosis are limited. The aim of this study was to identify attachment patterns in psychosis and examine demographic and clinical correlates across attachment groups. Latent profile analysis on attachment data from 588 participants who met criteria for non-affective psychosis was used to classify people into attachment classes. Four latent classes of attachment were identified: secure, insecure-anxious, insecure-avoidant and disorganised. Secure attachment was the most common attachment style, suggesting that a significant number of clients with psychosis are inherently resilient. Disorganised attachment was associated with a higher proportion of sexual and physical abuse and more severe positive symptoms compared to other attachment classes. This is not only the largest study to examine attachment styles, their demographic and clinical profile, and the clinical profile of disorganised attachment more specifically, in psychosis, but also the first study to use a validated self-report measure of attachment in psychosis to identify four classes of attachment style. Findings advance developmental models of attachment and psychosis; participants with disorganised attachment report more frequent trauma history and more severe psychotic symptoms.

Sun Exposure and Psychotic Experiences

OBJECTIVE

Sun exposure is considered the single most important source of vitamin D. Vitamin D deficiency has been suggested to play a role in the etiology of psychotic disorders. The aim of the present study was to evaluate the association between sun exposure and psychotic experiences (PEs) in a general population sample of Swedish women.

METHODS

The study population included participants from The Swedish Women's Lifestyle and Health cohort study. The 20-item community assessment of psychic experiences (CAPEs) was administered between ages 30 and 50 to establish PEs. Sun exposure as measured by (1) sunbathing holidays and (2) history of sunburn was measured between ages 10 and 39. The association between sun exposure and PEs was evaluated by quantile regression models.

RESULTS

34,297 women were included in the analysis. Women who reported no sunbathing holidays and 2 or more weeks of sunbathing holidays scored higher on the CAPE scale than women exposed to 1 week of sunbathing holidays across the entire distribution, when adjusting for age and education. Similarly, compared with women who reported a history of one sunburn, the women with none or two or more sunburns showed higher scores on the CAPE scale.

CONCLUSION

The results of the present study suggest that, in a population-based cohort of middle aged women, both low and high sun exposure is associated with increased level of positive PEs.

Paternal and maternal ages have contrasting associations with self-reported schizophrenia liability

BACKGROUND

Older paternal age predicts schizophrenia diagnosis in offspring. If this relationship reflects a pathogenic process, paternal age should predict the expression of subclinical schizophrenia liability (schizotypy). We hypothesized that paternal and maternal ages predict positive, negative, and disorganized features of schizotypy, that family history of psychosis moderates the relationship of paternal age with schizotypy, and that stress sensitivity mediates the relationship of maternal age with schizotypy.

METHOD

Two studies are reported, each of undergraduates (n=500 and n=211) who completed the Schizotypal Personality Questionnaire. The second was designed to replicate and extend the first and included assessment of stress sensitivity.

RESULTS

In Study 1, older paternal age and younger maternal age predicted greater positive schizotypy (β=.13 and β=-.19, respectively). Parental ages did not predict negative or disorganized features and family history did not moderate the paternal age association. In Study 2, the same pattern of associations between parental ages and schizotypy components was observed. Additionally, stress sensitivity partially mediated the association of maternal age with positive schizotypy whereas it did not contribute to the paternal age association.

CONCLUSION

The association between older paternal age and schizophrenia extends to self-reported positive features of schizophrenia liability, consistent with the notion that this relationship arises from a pathogenic process, such as de novo mutations. Importantly, younger maternal age was an equally potent predictor of positive schizotypy, with its association partially mediated by stress sensitivity.

A New Perspective on Delusional States - Evidence for Claustrum Involvement

Delusions are a hallmark positive symptom of schizophrenia, although they are also associated with a wide variety of other psychiatric and neurological disorders. The heterogeneity of clinical presentation and underlying disease, along with a lack of experimental animal models, make delusions exceptionally difficult to study in isolation, either in schizophrenia or other diseases. To date, no detailed studies have focused specifically on the neural mechanisms of delusion, although some studies have reported characteristic activation of specific brain areas or networks associated with them. Here, we present a novel hypothesis and extant supporting evidence implicating the claustrum, a relatively poorly understood forebrain nucleus, as a potential common center for delusional states.

Attachment in schizophrenia--implications for research, prevention, and treatment

Attachment is a promising area for elucidating psychosocial mechanisms important for development, prevention, and treatment of schizophrenia. This report gives a short summary of studies of attachment in psychosis. It was found that dismissing and disorganized forms of attachment were over-represented in psychosis. Evidence pointed to associations between a dismissing attachment pattern and positive psychotic symptoms, negative symptoms, and poor engagement with services. Furthermore, insecure attachment was found to predict impaired recovery from negative symptoms. Possible major risk processes in development linking dismissing attachment to symptom development were externalizing and deactivation of affects and poor mentalization. For a disorganized form of attachment, possible risk mechanisms were heightened stress-sensitivity and dissociation. Based on this initial evidence, further research in attachment in psychosis focusing on these risk mechanisms seems warranted. In addition, the evidence supported a focus on attachment-related risk processes to enhance the prevention and treatment of psychosis.

The psychosis spectrum in a young U.S. community sample: findings from the Philadelphia Neurodevelopmental Cohort

Little is known about the occurrence and predictors of the psychosis spectrum in large non-clinical community samples of U.S. youths. We aimed to bridge this gap through assessment of psychosis spectrum symptoms in the Philadelphia Neurodevelopmental Cohort, a collaborative investigation of clinical and neurobehavioral phenotypes in a prospectively accrued cohort of youths, funded by the National Institute of Mental Health. Youths (age 11-21; N=7,054) and collateral informants (caregiver/legal guardian) were recruited through the Children's Hospital of Philadelphia and administered structured screens of psychosis spectrum symptoms, other major psychopathology domains, and substance use. Youths were also administered a computerized neurocognitive battery assessing five neurobehavioral domains. Predictors of psychosis spectrum status in physically healthy participants (N=4,848) were examined using logistic regression. Among medically healthy youths, 3.7% reported threshold psychotic symptoms (delusions and/or hallucinations). An additional 12.3% reported significant sub-psychotic positive symptoms, with odd/unusual thoughts and auditory perceptions, followed by reality confusion, being the most discriminating and widely endorsed attenuated symptoms. A minority of youths (2.3%) endorsed subclinical negative/disorganized symptoms in the absence of positive symptoms. Caregivers reported lower symptom levels than their children. Male gender, younger age, and non-European American ethnicity were significant predictors of spectrum status. Youths with spectrum symptoms had reduced accuracy across neurocognitive domains, reduced global functioning, and increased odds of depression, anxiety, behavioral disorders, substance use and suicidal ideation. These findings have public health relevance for prevention and early intervention.

Service use for mental health problems in people with delusional-like experiences: a nationwide population based survey

Objective

Previous population-based studies have found that delusional-like experiences (DLEs) are prevalent in the community, and are associated with a wide range of mental health disorders. The aim of the study was to investigate mental health service use by people with DLEs.

Methods

Subjects were drawn from the Australian National Survey of Mental Health and Wellbeing 2007 of 8 841community residents aged between 16 and 85 years. The Composite International Diagnostic Interview (CIDI) was used to identify DLEs. Service utilization was assessed using a module that elicited information about hospital admissions, consultations with various health professionals, and prescription medication use. This study focussed on service use for mental health problems. We used logistic regression to examine the association, adjusting for potential confounding factors.

Results

Of 8 773 included participants, 8.4% (n = 776) positively endorsed one or more DLEs. With respect to consultations for mental health needs, individuals who endorsed DLEs were more likely to consult health professionals compared with those who did not endorse DLEs. Individuals with DLEs were also more likely to use prescription medicine. When we repeated the main analysis in a subgroup excluding any CIDI diagnosis of mental health disorders the results remained largely unchanged.

Conclusions

DLEs are common in the general population, and individuals with DLEs have an increased rate of accessing services for their mental health needs. Individuals endorsing both DLEs and increased help-seeking may identify a group of vulnerable people who have increased risk of developing psychotic illnesses later in life. This needs closer scrutiny in longitudinal prospective studies.

Delusion proneness in nonclinical individuals and cognitive insight: the contributions of rumination and reflection

Although previous research demonstrates that clinical individuals with delusions score low on one of the facets of cognitive insight, self-reflection, and high on the other facet, self-certainty, analogous studies of delusion proneness in nonclinical individuals have found that delusion proneness in nonclinical individuals associates with higher levels of both self-certainty and self-reflection. The present study sought to reconcile these inconsistent results by examining the contributions of different facets of self-reflection, rumination and reflection, to delusion proneness. One hundred fifty-two individuals completed three questionnaires: the Beck Cognitive Insight Scale (BCIS), the Peters et al. Delusions Inventory (PDI), and the Rumination-Reflection Questionnaire (RRQ). The results showed that the individuals scoring higher on delusion proneness demonstrated higher levels of both self-certainty and self-reflection on the BCIS as well as higher levels of rumination and reflection on the RRQ. As predicted, the strength of the relationship between BCIS self-reflection and delusion proneness was diminished when rumination was controlled for. These findings suggest that the previously observed positive relation between BCIS self-reflection and nonclinical delusion proneness might be driven, in part, by the ruminative aspect of self-reflection.

The association between adult attachment style and delusional-like experiences in a community sample of women

Community-based surveys have found that many otherwise well individuals endorse delusional-like experiences (DLEs). There is extensive literature that describes the demographic and psychosocial correlates of DLE; however, we know little about the association between DLE and attachment style. The association between DLEs (assessed by the Peters Delusional Inventory [PDI]) and interpersonal relationship style (as assessed by the Adult Attachment Questionnaire and the Dyadic Adjustment Scale) was examined in 3360 women. When adjusted for the presence of depressive and anxiety symptoms, high scores on the PDI (lowest versus highest quartiles) were associated with a) difficulties in adult attachment style particularly in the discomfort with closeness and preoccupation with relationships subscales and b) conflictual dyadic adjustment (adjusted odds ratios and 95% confidence intervals, 2.43 and 1.94-3.04, 2.50 and 1.99-3.14, and 2.90 and 1.38-6.06, respectively). The association between adult attachment style and DLE provides new clues into the causal pathway underpinning these common experiences.

Classes of psychotic experiences in Kenyan children and adolescents

Psychotic-like experiences (PLEs) have been observed worldwide in both adults and children outside the context of a clinical disorder. In the current study, we investigate the prevalence and patterns of PLEs among children and adolescents in Kenya. Among 1,971 students from primary and secondary schools around Nairobi (aged 8-19), 22.1 % reported a lifetime history of a psychotic experience, and 16.3 % reported this unrelated to sleep or drugs. Psychotic experiences were more common in males compared to females. LCA resulted in a three-class model comprised of a normative class (83.3 %), a predominately hallucinatory class (Type 1 psychosis: 9.6 %), and a pan-psychotic class (Type 2 psychosis: 7.2 %). These results indicate that PLEs are prevalent in children and adolescents, and the distributions of symptom clusters are similar to that found in adulthood. The relationship of specific PLEs to the future development of psychotic disorder, functional impairment or distress will require further study.

The heritability of delusional-like experiences

OBJECTIVE

Delusional-like experiences (DLE) are common in the general community and are associated with a family history of mental illness. The aim of this study was to estimate the heritability of DLE.

METHOD

The Peter's Delusional Inventory (PDI) was administered to a population-based cohort of mothers (n = 2861, aged 35-67 years) and their adult offspring (n = 3079, aged 18-23 years). Heritability of DLE was estimated from the sum scores of the 21 item PDI under the assumption that the covariance between mother-offspring scores is attributable to shared additive genetic factors.

RESULTS

The means (medians and standard deviations) for the total PDI scores for the mothers and their offspring were 3.6 (3.0, 3.0) and 5.0 (4.0, 3.5), respectively. The Pearson correlation coefficient between mother and offspring PDI scores was 0.17 (P < 0.001). The heritability was estimated to be 0.35 (standard error 0.04).

CONCLUSION

Heritable factors contribute to over a third of the variance of PDI scores in this population. In light of the association between a family history of a wide range of mental disorders and DLE, these experiences may represent a useful quantitative endophenotype for genetic studies of common mental disorders in population settings.

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

PURPOSE

The Peters et al. Delusions Inventory (PDI) is a commonly used instrument to measure delusion proneness in the general population and includes dimensions that measure distress, preoccupation, and conviction of unusual beliefs. This self-report scale has already been translated into several languages. However, there has not been a validated Taiwanese version previously reported. The aims of the present study were to translate and test the cross-cultural reliability and validity of the PDI in Taiwanese as well as to establish its sensitivity, specificity, and discriminative validity.

METHODS

We administered the questionnaire to a consecutive sample of 253 participants with (n = 154; clinical group including schizophrenia and affective psychosis) or without psychotic disorders (n = 99; non-clinical group). In addition to the Taiwanese version of the PDI (PDI-T), the Taiwanese version of the Brief Psychiatric Symptom Rating Scale (BSRS) was used to measure the severity of psychopathology. We tested the psychometric properties of the PDI-T, including its construct validity, internal consistency, test-retest reliability, concurrent, and discriminative validity.

RESULTS

Overall, the PDI-T showed good construct validity, internal consistency, and stability over time, and it was significantly correlated with the BSRS subscales of psychotic symptoms. The convergent and discriminative validity was satisfactory. The area under the receiver operating characteristic curve of the PDI-T was 0.752. This research found that the most appropriate PDI-T yes/no cut-off scores for determining the absence and presence of delusion proneness were 5 and 13.

CONCLUSIONS

The PDI is a reliable and valid instrument for measuring the dimensionality of delusion proneness and appears to complement subclinical psychosis assessment scales for both epidemiological and clinical research in Taiwan.

Anxiety and depressive disorders are associated with delusional-like experiences: a replication study based on a National Survey of Mental Health and Wellbeing

OBJECTIVES

There is growing evidence that delusional-like experiences (DLE) are associated with common mental disorders. In particular, a National Mental Health Survey conducted in Australia during 2007 reported an association between DLE and both anxiety disorder and major depressive disorder (MDD). However, the previous study did not examine this association with respect to subtypes of anxiety disorder nor with severity of MDD. The aim of this study was to examine the associations between DLE and both anxiety disorder and MDD in more detail based on an independent population sample.

DESIGN

Cross-sectional study.

SETTING

Subjects were drawn from the Australian Survey of Mental Health and Wellbeing 1997 using a stratified multistage area sampling of persons living in private dwellings in all States and Territories of Australia.

PARTICIPANTS

Approximately 13 600 private dwellings were initially selected with one person aged 18 years or older from each dwelling invited to participate. In total, 10 641 individuals participated in the survey.

PRIMARY AND SECONDARY OUTCOME MEASURES

The Composite International Diagnostic Interview was used to identify individuals with DLE and Diagnostic and Statistical Manual of Mental Disorder, Fourth Edition (DSM IV) lifetime diagnoses of anxiety disorders and MDD. The influence of various anxiety disorders and MDD on DLE was assessed with logistic regression.

RESULTS

Having a lifetime diagnosis of either any anxiety disorder or MDD was significantly associated with the endorsement of DLE. The association was found for each of the main anxiety disorders when examined separately. There was a dose-response relationship between increasing severity of MDD and higher odds of DLE endorsement.

CONCLUSIONS

DLE are associated with a wide range of anxiety disorders and are more prevalent in those with MDD. Understanding the relationship between DLE, anxiety disorders and depression may provide insights into shared pathways that underpin both psychotic disorders and common mental disorders.

The association between delusional-like experiences, and tobacco, alcohol or cannabis use: a nationwide population-based survey

BACKGROUND

Previous population-based studies have found that delusional-like experiences (DLE) are prevalent in the community, and are associated with a wide range of mental health disorders including substance use. The aim of the study was to explore the association between DLE and three commonly used substances--tobacco, alcohol and cannabis.

METHODS

Subjects were drawn from the Australian National Survey of Mental Health and Wellbeing 2007. The Composite International Diagnostic Interview was used to identify DLE, common psychiatric disorders, and substance use. We examined the relationship between the variables of interest using logistic regression, adjusting for potential confounding factors.

RESULTS

Of 8,773 participants, 8.4% (n=776) subjects endorsed one or more DLE. With respect to tobacco use, compared to nonusers, DLE were more common in those who (a) had daily use, (b) commenced usage aged 15 years or less, and (c) those who smoked heavily (23 or more cigarettes per day). Participants with cannabis use disorders were more likely to endorse DLE; this association was most prominent in those with an onset of 16 years or younger. In contrast, the pattern of association between DLE versus alcohol use or dependence was less consistent, however those with early onset alcohol use disorders were more likely to endorse DLE probe items.

CONCLUSIONS

While cannabis use disorders have been previously linked with DLE, our findings linking alcohol and tobacco use and DLE suggest that the influence of these substances on psychosis-related outcomes warrants closer scrutiny in longitudinal prospective studies.

The association between family history of mental disorder and delusional-like experiences: a general population study

Recent studies have indicated that isolated delusional-like experiences (DLE) are common in the general population. Furthermore, there is preliminary evidence to suggest that these experiences are more common in those with a family history of mental disorders. We had the opportunity to explore the association between family history of a wide range of mental disorders and DLE in an Australian general population survey. The Australian National Survey of Mental Health and Wellbeing 2007 examined 8,841 adult community residents. The Composite International Diagnostic Interview was used to generate various DSM-IV lifetime diagnoses and to assess DLE. The participants were asked to report mental disorders in their first-degree relatives. The influence of family history of mental disorders on DLE endorsement was assessed with logistic regression, with adjustments for age, sex, and the presence of comorbid psychiatric diagnoses in the respondents. A family history of anxiety, depression, schizophrenia, bipolar disorder, or alcohol or illicit drug abuse/dependence was each significantly associated with endorsement of DLE, and these associations remained significant when we adjusted for the presence of mental illness in the respondents. When we examined a more restrictive definition of DLE, only a family history of depression and schizophrenia remained significantly associated with DLE. DLE are associated with a family history of a wide range of mental disorders. These findings suggest that familial factors associated with DLE may be shared with a wide range of common mental disorders.

The association between physical health and delusional-like experiences: a general population study

OBJECTIVE

Delusional-like experiences (DLE) are prevalent in the community. Recent community based studies have found that DLE are more common in those with depression and anxiety disorders, and in those with subclinical symptoms of depression and anxiety. Chronic physical disorders are associated with comorbid depression and anxiety; however, there is a lack of evidence about the association of DLE with common physical conditions. The aim of this study was to explore associations between the common physical disorders and DLE using a large population sample.

METHODS

Subjects were drawn from the Australian National Survey of Mental Health and Wellbeing 2007, a national household survey of 8841 residents aged between 16 and 85 years. The presence of DLE, selected common physical disorders and symptoms were assessed using a modified World Mental Health Composite International Diagnostic Interview (CIDI) schedule. We examined the relationship between DLE, and physical health-related variables using logistic regression, with adjustments for potential confounding factors.

RESULTS

Of the 8771, 776 (8.4%) subjects positively endorsed one or more DLE. Of the six physical disorders examined, only diabetes and arthritis were significantly associated with the endorsement of DLE. Of the seven broad physical symptoms explored, only hearing problems were consistently associated with DLE.

CONCLUSION

Delusional-like experiences are common in the Australian community, and are associated with selected chronic physical disorders and with impaired hearing. The direction of causality between these variables warrants closer research scrutiny.

The association between general psychological distress and delusional-like experiences: a large population-based study

BACKGROUND

Delusional-like experiences (DLE) are prevalent in the community, and are associated with the both clinical and subclinical depression and anxiety. The aim of this study was to explore the association between general psychological distress and DLE adjusting for the presence of psychiatric disorders in a large population-based sample.

METHODS

Subjects were drawn from the Australian National Survey of Mental Health and Wellbeing 2007 (n=8841). DLE were assessed using a modified World Mental Health Composite International Diagnostic Interview (CIDI) schedule, and psychological distress was measured using the Kessler-10 (K10) short questionnaire. We examined the relationship between DLE and quartiles of K10 scores using logistic regression, adjusting for depression and anxiety disorders, and other potential confounding factors. The analyses were also repeated in the subgroup of the sample who were free of lifetime clinical diagnoses.

RESULTS

Of the participants, 776 (8.4%) endorsed one or more DLE. Individuals with moderate and severe psychological distress were two to three times more likely to endorse DLE. The association remained significant after adjusting for potential confounding factors, and in the subgroup of the population who remained after excluding those who met criteria for lifetime diagnosis for any mental disorder.

CONCLUSION

While DLE have traditionally been associated with psychotic disorders, our results suggest that they are associated with non-specific psychological distress in otherwise-well individuals.

Psychotic-like experiences in major depression and anxiety disorders: a population-based survey in young adults

OBJECTIVE

Population-based surveys have confirmed that psychotic-like experiences are prevalent in the community. However, it is unclear if these experiences are associated with common mental disorders. The aim of this study was to examine the prevalence of psychotic-like experiences in those with affective and anxiety disorders.

METHODS

Subjects were drawn from the Mater-University of Queensland Study of Pregnancy. Delusion-like experiences were assessed with the Peters Delusional Inventory (PDI). The Composite International Diagnostic Interview (CIDI) was used to identify individuals with Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) lifetime diagnoses of major depression, anxiety disorder, substance use/dependence, and psychotic disorders. The influence of affective and anxiety disorders on PDI and CIDI psychosis-related items' scores were assessed with logistic regression, with adjustments for age, sex, and the presence of the other comorbid psychiatric diagnoses.

RESULTS

Having either a lifetime diagnosis of major depressive disorder or an anxiety disorder was associated with significantly higher PDI total scores (highest vs lowest quartile adjusted odds ratios [ORs] and 95% confidence intervals [CIs] = 4.43, 3.09-6.36; 3.08, 2.26-4.20, respectively). The odds of endorsing any CIDI hallucination or delusion item was increased in those with a major depressive or anxiety disorder. The presence of current anxiety disorder symptoms was significantly associated with PDI score (OR = 5.81, 95% CI = 3.68-9.16).

CONCLUSION

While psychotic-like experiences are usually associated with psychotic disorders, individuals with depression and anxiety are also more likely to report these symptoms compared with well individuals. Psychotic-like experiences are associated with a range of common mental disorders.

Correlation between attenuated psychotic experiences and depressive symptoms among Japanese students

AIMS

To examine the emergence of attenuated psychotic experiences, self-disturbance or affective symptoms among younger subjects in the general population and to investigate the intergroup differences on each symptom between adolescents and post-adolescents.

METHODS

A total of 781 participants, 496 university students (mean age: 19.3 +/- 1.1 years) and 285 high school students (mean age: 16.0 +/- 0.3 years), were administered self-reported questionnaires. Psychotic prodromal symptoms were evaluated using the PRIME Screen-Revised (PS-R), a 12-item self-reported questionnaire. To measure the cognitive, emotional and physical symptoms associated with depression, the Zung Self-rating Depression Scale (ZSDS), a 20-item self-reported questionnaire, was administered.

RESULTS

There were no intergroup differences on the factor score of the PS-R, except the self-demarcation factor (post-adolescents > adolescents), whereas there were significant differences in the factor score of the ZSDS, except for the anxiety factor. Among the post-adolescents, the factors of the PS-R showed a moderate correlation to the cognitive factor on the ZSDS; among the adolescents, the PS-R factors showed a greater correlation to the anxiety factor on the ZSDS than other factors. There were no differences in the distribution of each item of the PS-R between the two groups.

CONCLUSIONS

The disturbance of self results in difficulty to precisely objectify, especially among adolescents, which would induce more primitive reactions such as agitation, irritability or anxiety; probably, the self disturbance would become an explicit symptom from an implicit experience with advancing age of the subject. Although these data are only preliminary, they could explain the pathway of progression prior to the onset of psychosis, from disturbance within the self to exaggerated self-absorption.

Dietary intake of fish, omega-3, omega-6 polyunsaturated fatty acids and vitamin D and the prevalence of psychotic-like symptoms in a cohort of 33,000 women from the general population

BACKGROUND

Low intake of fish, polyunsaturated fatty acids (PUFA) and vitamin D deficiency has been suggested to play a role in the development of schizophrenia. Our aim was to evaluate the association between the intake of different fish species, PUFA and vitamin D and the prevalence of psychotic-like symptoms in a population-based study among Swedish women.

METHODS

Dietary intake was estimated using a food frequency questionnaire among 33,623 women aged 30-49 years at enrollment (1991/92). Information on psychotic-like symptoms was derived from a follow-up questionnaire in the years 2002/03. Participants were classified into three predefined levels: low, middle and high frequency of symptoms. The association between diet and psychotic-like symptoms was summarized in terms of relative risks (RR) and corresponding 95% confidence intervals and was evaluated by energy-adjusted multinomial logistic regression.

RESULTS

18,411 women were classified as having a low level of psychotic-like symptoms, 14 395 as middle and 817 as having a high level. The risk of high level symptoms was 53% (95% CI, 30-69%) lower among women who ate fish 3-4 times per week compared to women who never ate fish. The risk was also lower for women with a high intake of omega-3 and omega-6 PUFA compared to women with a lower intake of these fatty acids. The effect was most pronounced for omega-6 PUFAs. The RR comparing the highest to the lowest quartile of omega-6 PUFAs intake was 0.78 (95% CI, 0.64-0.97). The associations were J-shaped with the strongest reduced risk for an intermediate intake of fish or PUFA. For fatty fish (herring/mackerel, salmon-type fish), the strongest inverse association was found for an intermediate intake (RR: 0.81, 95% CI, 0.66-0.98), whereas a high intake of fatty fish was associated with an increased risk of psychotic-like symptoms (RR: 1.90, 95% CI, 1.34-2.70). Women in the highest compared with the lowest quartile of vitamin D consumption experienced a 37% (95% CI, 22-50%) lower risk of psychotic-like symptoms.

CONCLUSION

Our findings raise a possibility that adult women with a high intake of fish, omega-3 or omega-6 PUFA and vitamin D have a lower rate of psychotic-like symptoms.

The prevalence and correlates of hallucinations in Australian adolescents: results from a national survey

There is an emerging interest in children and adolescents who have hallucinations and other psychotic-like experiences to enable identification of those potentially at risk for schizophrenia in adulthood. This study examines the prevalence, demographic and clinical correlates of hallucinations in the adolescent subgroup of the Australian National Survey of Mental Health and Well-Being. Participants were a nationally representative sample of 1261 adolescents aged 13-17 years. Adolescents completed self-report questionnaires with two questions relating to hallucinations and questions pertaining to depressive symptoms and cannabis use. Parents completed the Child Behavior Checklist (CBCL) and the Diagnostic Interview Schedule for Children (DISC-IV). Hallucinations were reported by 8.4% of adolescents. Those living in blended or sole parent families were more likely to report hallucinations than those living with both biological parents (OR 3.27; 95% CI 1.93, 5.54; OR 2.60; 95% CI 1.63, 4.13 respectively). Hallucinations were more prevalent in adolescents who scored in the highest decile of the CBCL or had elevated depression symptoms (OR 3.30; 95% CI 2.10, 5.20; OR 5.02; 95% CI 3.38, 7.45 respectively). Hallucinations were associated with depressive disorder (OR 2.70; 95% CI 1.16, 6.28) and were more prevalent in those adolescents who had smoked cannabis more than twice in the month prior to the survey (OR 3.27; 95% CI 1.76, 6.08). Hallucinations occur relatively frequently in adolescents and are associated with a range of demographic and clinical correlates. Further research may assist in understanding the variable trajectory of children and adolescents who hallucinate.