Dimensional, non-taxonic latent structure of psychotic symptoms in a student sample

The developmental course of adolescent paranoia: a longitudinal analysis of the interacting role of mistrust and general psychopathology

Paranoia is the erroneous idea that people are targeting you for harm, and the cognitive model suggests that symptoms increase with emotional and relational distress. A factor potentially associated with paranoia is mistrust, a milder form of suspiciousness. This study investigated the longitudinal course of non-clinical paranoia in a sample of 739 students (age range 10-12 at baseline assessment, 12-14 at second assessment) using data from the Social Mistrust Scale (SMS) and the paranoia subscale of the Specific Psychotic Experiences Questionnaire (SPEQ). Prevalence of mistrustful and high paranoia children was 14.6 and 15% respectively. Independently, baseline internalizing symptoms (b = 0.241, p < 0.001) and mistrust (b = 0.240, p < 0.001) longitudinally predict paranoia after controlling for confounders. The interaction of mistrust and internalizing symptoms at T1 increases the possibility of the onset of paranoia at T2. Therefore, the effect of mistrust on paranoia is more marked when internalizing symptoms are higher. Our results confirm the role of mistrust as a factor involved in the developmental trajectory of paranoia in adolescence, enhanced by the presence of internalizing symptoms. The implications of these results are both theoretical and clinical, as they add developmental information to the cognitive model of paranoia and suggests the assessment and clinical management of mistrust and internalizing symptoms in youth may be useful with the aim of reducing the risk of psychotic experiences.

Latent structure of psychotic-like experiences in adolescents: Evidence from a multi-method taxometric study of a school-based sample in Ghana

Psychotic-like experiences (PLEs) are subclinical psychotic symptoms that occur outside the context of sleep or are unrelated to drug use. PLEs of varying severity are reportedly very common in adolescence. However, there are concerns about whether the structure of PLEs among adolescents is latently dimensional or categorical ("taxonic"). The current study investigates the latent structure of PLEs in 1,886 adolescents recruited from senior high schools in Ghana. Four multivariate taxometric procedures (MAMBAC, MAXEIG, l-Mode and MAXSLOPE) were applied to analyze the data. Across the taxometric procedures, there was evidence that a dimensional structure underpins positive PLEs, negative PLEs and a combination of positive and negative PLEs. The findings suggest that PLEs are distributed in the adolescent population at differing degrees/severity and that evidence of discontinuity between milder and more severe PLEs is non-existent. The findings highlight the importance of incorporating a dimensional assessment of PLEs into the existing categorical approach so that differences between people can been seen as quantitative variations along the PLEs continuum.

Dimensions over categories: a meta-analysis of taxometric research

Taxometric procedures have been used extensively to investigate whether individual differences in personality and psychopathology are latently dimensional or categorical ('taxonic'). We report the first meta-analysis of taxometric research, examining 317 findings drawn from 183 articles that employed an index of the comparative fit of observed data to dimensional and taxonic data simulations. Findings supporting dimensional models outnumbered those supporting taxonic models five to one. There were systematic differences among 17 construct domains in support for the two models, but psychopathology was no more likely to generate taxonic findings than normal variation (i.e. individual differences in personality, response styles, gender, and sexuality). No content domain showed aggregate support for the taxonic model. Six variables - alcohol use disorder, intermittent explosive disorder, problem gambling, autism, suicide risk, and pedophilia - emerged as the most plausible taxon candidates based on a preponderance of independently replicated findings. We also compared the 317 meta-analyzed findings to 185 additional taxometric findings from 96 articles that did not employ the comparative fit index. Studies that used the index were 4.88 times more likely to generate dimensional findings than those that did not after controlling for construct domain, implying that many taxonic findings obtained before the popularization of simulation-based techniques are spurious. The meta-analytic findings support the conclusion that the great majority of psychological differences between people are latently continuous, and that psychopathology is no exception.

A systematic review of genome-wide research on psychotic experiences and negative symptom traits: new revelations and implications for psychiatry

We present a systematic review of genome-wide research on psychotic experience and negative symptom (PENS) traits in the community. We integrate these new findings, most of which have emerged over the last four years, with more established behaviour genetic and epidemiological research. The review includes the first genome-wide association studies of PENS, including a recent meta-analysis, and the first SNP heritability estimates. Sample sizes of <10 000 participants mean that no genome-wide significant variants have yet been replicated. Importantly, however, in the most recent and well-powered studies, polygenic risk score prediction and linkage disequilibrium (LD) score regression analyses show that all types of PENS share genetic influences with diagnosed schizophrenia and that negative symptom traits also share genetic influences with major depression. These genetic findings corroborate other evidence in supporting a link between PENS in the community and psychiatric conditions. Beyond the systematic review, we highlight recent work on gene-environment correlation, which appears to be a relevant process for psychotic experiences. Genes that influence risk factors such as tobacco use and stressful life events are likely to be harbouring 'hits' that also influence PENS. We argue for the acceptance of PENS within the mainstream, as heritable traits in the same vein as other sub-clinical psychopathology and personality styles such as neuroticism. While acknowledging some mixed findings, new evidence shows genetic overlap between PENS and psychiatric conditions. In sum, normal variations in adolescent and adult thinking styles, such as feeling paranoid, are heritable and show genetic associations with schizophrenia and major depression.

The Latent Taxonicity of Schizotypy in Biological Siblings of Probands With Schizophrenia

If schizotypy is a taxonic liability for schizophrenia with a general population prevalence of ~10%, it should also be taxonic among biological siblings of probands with schizophrenia. Moreover, assuming this is so, siblings' schizotypy class membership should be predicted by probands' familial load for psychotic disorder and clinical severity, consistent with a multifactorial polygenic threshold model of schizophrenia. We tested these hypotheses in the Genetic Risk and Outcome of Psychosis (GROUP) Study where siblings of probands (n = 792) and unaffected controls (n = 559) provided self-report ratings on the Community Assessment of Psychic Experiences (CAPE). Maximum covariance analyses of control group ratings led to the identification of CAPE items sensitive to nonredundant positive and negative schizotypy classes in the control group (prevalence = 7.9% and 11.1%, respectively). When the same taxonic solution was applied to siblings' CAPE rating, taxometric analyses yielded evidence for larger positive and negative schizotypy classes among siblings (prevalence = 14.1% and 21.8%, respectively). Whereas probands' familial loads for bipolar disorder or drug use disorders did not predict siblings' membership in the schizotypy classes, probands' familial load for psychotic disorder did. Siblings were more likely to be members of the positive schizotypy class where their probands were more severely affected. The pattern of findings is consistent with Meehl's argument that schizotypy reflects liability for schizophrenia.

Genome-wide analysis of adolescent psychotic-like experiences shows genetic overlap with psychiatric disorders

This study aimed to test for overlap in genetic influences between psychotic-like experience traits shown by adolescents in the community, and clinically-recognized psychiatric disorders in adulthood, specifically schizophrenia, bipolar disorder, and major depression. The full spectra of psychotic-like experience domains, both in terms of their severity and type (positive, cognitive, and negative), were assessed using self- and parent-ratings in three European community samples aged 15-19 years (Final N incl. siblings = 6,297-10,098). A mega-genome-wide association study (mega-GWAS) for each psychotic-like experience domain was performed. Single nucleotide polymorphism (SNP)-heritability of each psychotic-like experience domain was estimated using genomic-relatedness-based restricted maximum-likelihood (GREML) and linkage disequilibrium- (LD-) score regression. Genetic overlap between specific psychotic-like experience domains and schizophrenia, bipolar disorder, and major depression was assessed using polygenic risk score (PRS) and LD-score regression. GREML returned SNP-heritability estimates of 3-9% for psychotic-like experience trait domains, with higher estimates for less skewed traits (Anhedonia, Cognitive Disorganization) than for more skewed traits (Paranoia and Hallucinations, Parent-rated Negative Symptoms). Mega-GWAS analysis identified one genome-wide significant association for Anhedonia within IDO2 but which did not replicate in an independent sample. PRS analysis revealed that the schizophrenia PRS significantly predicted all adolescent psychotic-like experience trait domains (Paranoia and Hallucinations only in non-zero scorers). The major depression PRS significantly predicted Anhedonia and Parent-rated Negative Symptoms in adolescence. Psychotic-like experiences during adolescence in the community show additive genetic effects and partly share genetic influences with clinically-recognized psychiatric disorders, specifically schizophrenia and major depression.

Psychotic-like experiences in help-seeking adolescents: Dimensional exploration and association with different forms of bullying victimization - A developmental social psychiatry perspective

BACKGROUND

Psychotic-like experiences (PLEs) are common in the general population and increase the risk of psychotic disorders. Adolescents are a high-risk group of this condition. Stressful events, such as bullying, have a role in the onset of PLEs. This study has several aims: (1) to assess PLEs in adolescents seeking help from a Child and Adolescent Mental Health Service, (2) to assess the association of PLEs with specific bullying victimization and (3) to assess difference in PLEs and victimizations by sex and age.

METHODS

Participants were help-seeking (HS) adolescents initially screened for PLEs. They completed an assessment including characteristics of PLEs and bullying victimization. We paid particular attention to different kinds of PLEs and victimization.

RESULTS

In total, 50 PLE-positive adolescents screened from 324 HS adolescents (15.4%) constituted the sample. Paranoia and verbal bullying were the PLEs and form of victimization most represented, respectively. Verbal bullying was strongly associated with paranoia (odds ratio (OR): 4.40, confidence interval (CI): 2.8-5.9, p < .001). Results remained significant after controlling for confounder (socio-demographic, anxiety, depression and for the latter analysis also other forms of victimization). Furthermore, social manipulation showed a strong association of paranoia and physical bullying with grandiosity. Verbal bullying was also associated with psychotic negative symptoms, but controlling for emotional symptoms and other victimization led to a reduction in the effect. Men were more involved in physical victimization and experienced grandiosity; on the contrary, late adolescents were most involved in social victimization and negative psychotic symptoms Conclusion: PLEs are relevant in HS adolescents. Bullying victimization interacts with the onset of these phenomena. In particular, verbal bullying predicted paranoia onset significantly.

The Psychosis Continuum: Testing a Bifactor Model of Psychosis in a General Population Sample

Although the factor structure of psychosis continues to be debated by taxonomists, recent studies have supported a bifactor model consisting of a general psychosis factor and 5 uncorrelated symptom-specific factors. While this model has received support in clinical samples, it has not been tested at the general population level. Analysis was conducted on Wave 2 of the National Epidemiologic Survey on Alcohol and Related Conditions (N = 34 653). Twenty-two psychotic symptoms were used as observed indicators of psychosis. These items were chosen based on their conceptual similarity to the items used in a similar study based on clinical samples. Confirmatory factor analysis and confirmatory bifactor modeling were used to test a variety of competing models. The best fitting model consisted of a general psychosis factor that was uncorrelated with 5 specific factors: positive, negative, disorganization, mania, and depression. These findings suggest that the bifactor model can be extended to general population samples, supporting the continuity between clinical and subclinical psychotic experiences. Theoretical and practical implications are discussed.

Dimensional psychotic experiences in adolescence: Evidence from a taxometric study of a community-based sample

Psychotic experiences of varying severity levels are common in adolescence. It is not known whether beyond a certain severity in the general population, psychotic experiences represent a categorically distinct phenomena to milder psychotic experiences. We employed taxometric analytic procedures to determine whether psychotic experiences in adolescence are taxonic (i.e. categorical) or dimensional. Six different psychotic experiences were assessed in a community sample of approximately 5000 adolescents. Three taxometric procedures were conducted. Across all procedures, there was no evidence of a taxon (i.e. a separate latent population) underlying psychotic experiences in adolescence. Rather, a dimensional structure was supported. The results support the notion that psychotic experiences are continuously distributed throughout the general population, and there is no clear discontinuity between milder and more severe psychotic experiences. Thus, these findings support the use of dimensional approaches to understanding psychotic experiences in etiological studies. In clinical practice, categorical cut-offs are needed: the present findings show that a 'natural' break point is not present for identifying severe psychotic experiences, and it is likely therefore that other criteria (such as general functioning) might better aid decision-making with regards to identifying individuals with severe psychotic experiences in need of care during adolescence.

Psychometric Properties of "Community Assessment of Psychic Experiences": Review and Meta-analyses

The Community Assessment of Psychic Experiences (CAPE) has been used extensively as a measurement for psychosis proneness in clinical and research settings. However, no prior review and meta-analysis have comprehensively examined psychometric properties (reliability and validity) of CAPE scores across different studies. To study CAPE's internal reliability--ie, how well scale items correlate with one another--111 studies were reviewed. Of these, 18 reported unique internal reliability coefficients using data at hand, which were aggregated in a meta-analysis. Furthermore, to confirm the number and nature of factors tapped by CAPE, 17 factor analytic studies were reviewed and subjected to meta-analysis in cases of discrepancy. Results suggested that CAPE scores were psychometrically reliable--ie, scores obtained could be attributed to true score variance. Our review of factor analytic studies supported a 3-factor model for CAPE consisting of "Positive", "Negative", and "Depressive" subscales; and a tripartite structure for the Negative dimension consisting of "Social withdrawal", "Affective flattening", and "Avolition" subdimensions. Meta-analysis of factor analytic studies of the Positive dimension revealed a tridimensional structure consisting of "Bizarre experiences", "Delusional ideations", and "Perceptual anomalies". Information on reliability and validity of CAPE scores is important for ensuring accurate measurement of the psychosis proneness phenotype, which in turn facilitates early detection and intervention for psychotic disorders. Apart from enhancing the understanding of psychometric properties of CAPE scores, our review revealed questionable reporting practices possibly reflecting insufficient understanding regarding the significance of psychometric properties. We recommend increased focus on psychometrics in psychology programmes and clinical journals.

The taxonicity of schizotypy: does the same taxonic class structure emerge from analyses of different attributes of schizotypy and from fundamentally different statistical methods?

Findings on the population distribution of schizotypy consistently point toward an underlying class structure. However, past research is methodologically homogeneous, chiefly involving analysis of attribute-specific indicators and coherent cut kinetic methods such as maximum covariance (MAXCOV) analysis. Two questions are examined. Are different or overlapping classes identified from different attributes of the schizophrenia phenotype? Do fundamentally different approaches to analysis yield consistent results? Participants (n=1074) completed the Schizotypal Personality Questionnaire (SPQ). Following item screening, MAXCOV analyses were conducted iteratively on attribute-specific item sets (cognitive-perceptual, interpersonal, and disorganized) and a general item set. Latent variable modeling (factor analysis, latent class analysis, and factor-mixture modeling) was used to examine the consistency of the MAXCOV results using items retained in the general set following MAXCOV analysis. Attribute-specific and general item sets gave taxonic MAXCOV curves and base rates of 8.4-10.4% and 3.6%, respectively. Classes were not independent. No latent variable model emerged as uniquely superior but five models distinguished a small high-scoring class populated by members of the MAXCOV general class. Different attributes distinguished overlapping yet nonredundant taxa, and a general schizotypy taxon identified with MAXCOV was also identified in latent variable modeling.

A model of psychosis and its relationship with impairment

PURPOSE

Some studies suggest that positive symptoms of psychosis-clinical and sub-clinical alike-reflect a single, continuously distributed dimension in the population. It is unknown, however, whether such a spectrum of positive psychotic experiences is non-linearly related to outcomes such as daily functioning. This work aims to characterize the relationship between positive psychosis and impairment.

METHODS

Data from the Office of National Statistics National Psychiatric Morbidity Surveys of Great Britain were used to establish measurement models of psychosis and impairment. Competing linear and nonlinear models of the relationship between the two latent variables were evaluated using mixture structural equation models.

RESULTS

Positive psychosis is best modeled by a continuous, normal distribution. Increases in positive psychosis correlate with roughly linear increases in impairment.

CONCLUSIONS

Positive psychotic symptoms occur throughout the population without a discrete, pathological threshold. Functional deficits are linearly associated with the psychosis at all points along the continuum, and a significant portion of the population experiences subclinical psychosis.

Categories versus dimensions in personality and psychopathology: a quantitative review of taxometric research

Taxometric research methods were developed by Paul Meehl and colleagues to distinguish between categorical and dimensional models of latent variables. We have conducted a comprehensive review of published taxometric research that included 177 articles, 311 distinct findings and a combined sample of 533 377 participants. Multilevel logistic regression analyses have examined the methodological and substantive variables associated with taxonic (categorical) findings. Although 38.9% of findings were taxonic, these findings were much less frequent in more recent and methodologically stronger studies, and in those reporting comparative fit indices based on simulated comparison data. When these and other possible confounds were statistically controlled, the true prevalence of taxonic findings was estimated at 14%. The domains of normal personality, mood disorders, anxiety disorders, eating disorders, externalizing disorders, and personality disorders (PDs) other than schizotypal yielded little persuasive evidence of taxa. Promising but still not definitive evidence of psychological taxa was confined to the domains of schizotypy, substance use disorders and autism. This review indicates that most latent variables of interest to psychiatrists and personality and clinical psychologists are dimensional, and that many influential taxonic findings of early taxometric research are likely to be spurious.

How much stress is needed to increase vulnerability to psychosis? A community assessment of psychic experiences (CAPE) evaluation 10 months after an earthquake in L'Aquila (Italy)

Since severe stress can induce mental disorder symptoms that interact with vulnerability factors, the Community Assessment of Psychic Experiences (CAPE) was evaluated in a population of 419 young adults who survived an earthquake; results were compared to a database of 1,057 'non-exposed' subjects. Unexpectedly, earthquake survivors showed lower CAPE scores for 'small' to 'medium' effect size. Post-trauma positive changes or re-appraisal for successful adaptation may explain these findings.

A questionnaire on treatment satisfaction and disease specific knowledge among patients with acute coronary syndrome. I: Are treatment satisfaction and disease specific knowledge continuous latent traits?

OBJECTIVE

To assess psychometric properties of a questionnaire covering treatment satisfaction and disease-specific knowledge among patients discharged after treatment for acute coronary syndrome.

METHODS

Comparative scaling of the questionnaire using latent class analysis (LCA) and exploratory factor analysis (EFA) in a consecutive sample of 2015 patients.

RESULTS

LCA revealed four qualitatively differing patterns of patients' knowledge and five distinct patterns of treatment satisfaction. EFA for patients' knowledge identified four uncorrelated "dimensions". Patient satisfaction was scored in a two-factor solution despite proven heterogeneity of persons.

CONCLUSIONS

LCA was helpful to identify classes of patients that cannot be scaled according to a latent trait model.

PRACTICE IMPLICATIONS

Specific patterns of insufficient disease-specific knowledge and satisfaction requiring specific interventions became visible.

Antibodies to infectious agents and the positive symptom dimension of subclinical psychosis: The TRAILS study

Infections have been suggested to play a role in the etiology of schizophrenia, but the evidence for this has been inconsistent. Schizophrenia patients have an increased risk of infections as a result of hospitalizations or life style factors. Therefore a study on early subclinical manifestations of psychosis in relation to virus infections is warranted. We examined whether serum antibodies against human Herpes viruses and Toxoplasma gondii were associated with subclinical symptoms of psychosis in adolescents. Data were collected as part of the TRacking Adolescents' Individual Lives Survey (TRAILS) cohort, a large prospective cohort of Dutch adolescents. A total of 1176 participants with an available Community Assessment of Psychic Experiences (CAPE) and an available blood sample were included in this analysis. Solid-enzyme immunoassay methods were used to measure the presence of immunoglobulin G (IgG) antibodies in serum to the Herpes virus family and to T. gondii. There was no significant association between serologic evidence of infection with human Herpes viruses or T. gondii and the risk of subclinical positive experience of psychosis. Subjects with a positive serological reaction to Epstein-Barr Virus (EBV) had higher scores on the positive dimension of psychosis measured by CAPE (b=0.03, P=0.02). This significant association was observed in males, but not in females. The current study suggests that there is no significant association between serological evidence of infection to human Herpes viruses and positive subclinical experience of psychosis, whereas there was an association between EBV infection and subclinical psychotic symptoms in boys.

Associations between psychotic-like symptoms and inattention/hyperactivity symptoms

OBJECTIVE

Our aim was to study the association between psychotic-like symptoms and inattention/hyperactivity symptoms in a general adolescent population.

SUBJECTS AND METHODS

The sample is based on a population-based prospective mother-child birth cohort, the Northern Finland Birth Cohort 1986. In the 15-16-year follow-up survey, the adolescents completed the Youth Self-Report questionnaire as well as the PROD-Screen questionnaire that addressed prodromal symptoms of psychosis. Meanwhile, their parents assessed inattention and hyperactive symptoms of their offspring by completing the Strengths and Weaknesses of ADHD Symptoms and Normal Behaviors questionnaire (N = 5,318). The cross-sectional associations between psychotic-like symptoms and inattention/hyperactivity symptoms were studied with logistic regression models.

RESULTS

The association between negative psychotic-like symptoms and inattention symptoms, especially the dreamy type of inattention symptoms (e.g., difficulties in organizing tasks, losing things, being forgetful), was statistically significant for both genders. Psychotic-like symptoms, however, were not associated with hyperactivity symptoms.

CONCLUSIONS

The present findings demonstrate that an association between psychotic-like symptoms and attentional dysfunction, which has been found in clinical samples, is also present in a general adolescent population.