An empirical analysis of latent structures underlying schizophrenic symptoms: a four-syndrome model

Cortical volume abnormalities in schizophrenia: Correlations with symptoms and cognitive impairment

BACKGROUND

Schizophrenic symptoms are known to segregate into reality distortion, negative and disorganization syndromes, but the correlates of these syndromes with regional brain structural change are not well established. Cognitive impairment is a further clinical feature of schizophrenia, whose brain structural correlates are the subject of conflicting findings.

METHODS

165 patients with schizophrenia were rated for symptoms using the PANSS, and cognitive impairment was indexed by estimated premorbid-current IQ discrepancy. Cortical volume was measured using surface-based morphometry in the patients and in 50 healthy controls. Correlations between clinical and cognitive measures and cortical volume were examined using whole-brain FreeSurfer tools.

RESULTS

No clusters of volume reduction were seen associated with reality distortion or disorganization. Negative symptom scores showed a significant inverse correlation with volume in a small cluster in the left medial orbitofrontal gyrus. Larger estimated premorbid-current IQ discrepancies were associated with clusters of reduced cortical volume in the left precentral gyrus and the left temporal lobe. The cluster of association with negative symptoms disappeared when estimated premorbid-current IQ discrepancy was controlled for.

CONCLUSIONS

This study does not provide support for an association between brain structural abnormality and reality distortion or disorganization syndromes in schizophrenia. The cluster of volume reduction found in the left medial orbitofrontal cortex correlated with negative symptoms may have reflected the association between this class of symptoms and cognitive impairment. The study adds to existing findings of an association between cognitive impairment and brain structural changes in the disorder.

Autobiographical memory and the self on the psychosis continuum: investigating their relationship with positive- and negative-like symptoms

Autobiographical memory is severely impaired in schizophrenia, but previous work has largely treated both as unitary concepts. Here, we examined how various dimensions of autobiographical memory relate to different aspects of psychosis. Participants were recruited from the general population (Study 1, N = 264) and a university subject pool (Study 2, N = 305). We examined different measures of autobiographical memory and self (i.e., involuntary memory, autobiographical recollection, self-knowledge and self-awareness), at the trait level in Study 1 and both trait and state levels in Study 2, as a function of positive-and negative-like symptoms of psychosis. Across both studies, positive and negative dimensions of psychosis were found to be related to an increase in involuntary memories (i.e., the spontaneous recall of personal memories), and to lower self-concept clarity and insight. Positive and negative dimensions of psychosis correlated differently with autobiographical recollection characteristics, measured at both trait (Studies 1 and 2) and state levels (Study 2). Positive-like symptoms (in particular hallucination-proneness) showed a stronger and more consistent pattern of correlations than negative-like symptoms. These findings call for a dimensional approach to the relationship between autobiographical memory and psychosis symptoms in clinical and non-clinical individuals, to better understand the breakdown of autobiographical memory in the psychopathology of psychosis.

Symptom dimensions and subgroups in childhood-onset schizophrenia

OBJECTIVE

This study investigated symptom dimensions and subgroups in the National Institute of Mental Health (NIMH) childhood-onset schizophrenia (COS) cohort and their similarities to adult-onset schizophrenia (AOS) literature.

METHOD

Scores from the Scales for the Assessment of Positive and Negative Symptoms (SAPS & SANS) from 125 COS patients were assessed for fit with previously established symptom dimensions from AOS literature using confirmatory factor analysis (CFA). K-means cluster analysis of each individual's scores on the best fitting set of dimensions was used to form patient clusters, which were then compared using demographic and clinical data.

RESULTS

CFA showed the SAPS & SANS data was well suited to a 2-dimension solution, including positive and negative dimensions, out of five well established models. Cluster analysis identified three patient groups characterized by different dimension scores: (1) low scores on both dimensions, (2) high negative, low positive scores, and (3) high scores on both dimensions. These groups had different Full scale IQ, Children's Global Assessment Scale (CGAS) scores, ages of onset, and prevalence of some co-morbid behavior disorders (all p<3.57E-03).

CONCLUSION

Our analysis found distinct symptom-based subgroups within the NIMH COS cohort using an established AOS symptom structure. These findings confirm the heterogeneity of COS and were generally consistent with AOS literature.

Dimensionality vs taxonicity of schizotypy: some new data and challenges ahead

Heterogeneity in the expression of schizotypy may arise from underlying dimensional processes or a taxonic population structure. In a 2-phase study, we tested the taxonicity of self-reported schizotypy within a general psychiatric sample (n = 109) and examined taxon validity by testing its association with clinical schizotaxia in follow-up subsamples. Taxometric analyses indicated a taxonic structure (schizotypy prevalence = 38.8%) provided the best description of the underlying population distribution. After a year, schizotypal (n = 14) and nonschizotypal (n = 14) subsamples returned for diagnosis of clinical schizotaxia by assessment of executive functioning, attention, memory, and negative symptoms. Seven patients met diagnostic criteria, all members of the schizotypy class. Schizotypy was associated with impaired attention and memory, more negative symptoms, poorer global functioning, and more extensive psychiatric histories. We reconcile inconsistencies in the literature by discussing threats to the validity of this and similar research on Meehl's taxonomic model of schizotypy, including conceptual limitations of the lexical hypothesis and conventions of factor analysis. Scrutiny of Meehl's model should involve disambiguation and better measurement of the schizotaxia-schizotypy phenotype.

Relationship between anticipatory, consummatory anhedonia and disorganization in schizotypy

BACKGROUND

The disorganized and negative dimensions of schizotypy are characterized by cognitive disorganization and anhedonia, respectively. The aim of the study was to investigate the relationships between these two dimensions of schizotypy by taking into account ambivalence and the distinction between consummatory and anticipatory anhedonia.

METHODS

Dimensional analysis and categorical analysis were performed on two different samples (N = 400 and 399) of university students. Self-reported scales were used to measure cognitive disorganization, anticipatory and consummatory anhedonia, and ambivalence. Dimensional analysis using confirmatory factorial analysis examined various models of disorganized and negative schizotypy and categorical analysis compared the scores on anticipatory, consummatory anhedonia and ambivalence scales between various groups of subjects presenting either disorganized schizotypy or negative schizotypy or free of schizotypy.

RESULTS

The disorganized dimension of schizotypy was characterized by schizotypal ambivalence and anticipatory anhedonia, while the negative dimension of schizotypy was characterized by anticipatory and consummatory anhedonia.

CONCLUSION

The results suggested firstly that ambivalence was not specific of disorganized schizotypy and secondly that anticipatory anhedonia was not specific of negative schizotypy.

Multilevel ordinal factor analysis of the positive and negative syndrome scale (PANSS)

Clinical assessments of the presence and severity of psychopathology are often collected by health care professionals in mental health services or clinical researchers trained to use semi-structured interviews. Clustering by interviewer or rater needs to be considered when performing psychometric analyses such as factor analysis or item response modelling as non-independence of observations arises in these situations. We apply more suitable multilevel methods to analyse ordinally scored Positive and Negative Syndrome Scale (PANSS) items. Our aim is to highlight the differences in results that occur when the data are analysed using a hierarchically sensitive approach rather than using a traditional (aggregated) analysis. Our sample (n = 507) consisted of patients diagnosed with schizophrenia who participated in a multi-centre randomized control clinical trial, the DIALOG study. Analyses reported and compared include an exploratory factor analysis as well as several recently published multifactor models re-estimated within a confirmatory analysis framework. Our results show that the fit of the model and the parsimony of the exploratory factor analysis (EFA) models indicated by the number of factors necessary to explain the inter-correlation among PANSS items improved significantly when data clustering is taken into account through multilevel analysis. Our modeling results support the pentagonal PANSS model first proposed by White et al. (1997). Copyright © 2014 John Wiley & Sons, Ltd.

The contribution of epidemiology to defining the most appropriate approach to genetic research on schizophrenia

Psychosis is thought to have a strong genetic component, but many efforts to discover the underlying putative schizophrenia genes have yielded disappointing results. In fact, no strong associations emerged in the first genome-wide association studies in psychiatry and weakly observed associations were not related to the candidate genes identified in previous studies. These partially successful findings may be explained by the fact that genetic research in psychiatry suffers from confounding issues related to phenotype definition, the considerable degree of phenotypic variability and diagnostic uncertainty, absence of specific neuropathological features and environmental influences. To make progress it is first necessary to deconstruct psychosis based on symptomatology, and then to correlate particular phenotypes with genetic variants. Moreover, it is time to conduct studies that define persistent aspects of the schizophrenic profile that are more likely to represent an underlying biological pathogenesis, as opposed to fluctuating symptoms that are possibly environmentally mediated. In fact, progress in understanding the etiology of schizophrenia will depend upon the availability of good measures of genetic liability as well as relevant environmental exposures during critical periods of an individual's life. If environmental and/or genetic factors are not precisely measured, it is impossible to study their independent effects or interactions.

Combining dimensional and categorical representation of psychosis: the way forward for DSM-V and ICD-11?

BACKGROUND

There is good evidence that psychotic symptoms segregate into symptom dimensions. However, it is still unclear how these dimensions are associated with risk indicators and other clinical variables, and whether they have advantages over categorical diagnosis in clinical practice. We investigated symptom dimensions in a first-onset psychosis sample and examined their associations with risk indicators and clinical variables. We then examined the relationship of categorical diagnoses to the same variables.

METHOD

We recruited 536 patients as part of a population-based, incidence study of psychosis. Psychopathology was assessed using the Schedules for Clinical Assessment in Neuropsychiatry (SCAN). A principal axis factor analysis was performed on symptom scores. The relationship of dimension scores with risk indicators and with clinical variables was then examined employing regression analyses. Finally, regression models were compared to assess the contribution of dimensions versus diagnosis in explaining these variables.

RESULTS

Factor analysis gave rise to a five-factor solution of manic, reality distortion, negative, depressive and disorganization symptom dimensions. The scores of identified dimensions were differentially associated with specific variables. The manic dimension had the highest number of significant associations; strong correlations were observed with shorter duration of untreated psychosis, acute mode of onset and compulsory admission. Adding dimensional scores to diagnostic categories significantly increased the amount of variability explained in predicting these variables; the reverse was also true but to a lesser extent.

CONCLUSIONS

Categorical and dimensional representations of psychosis are complementary. Using both appears to be a promising strategy in conceptualising psychotic illnesses.

Plasma homovanillic acid differences in clinical subgroups of first episode schizophrenic patients

This study evaluates the relationship between plasma homovanillic acid (pHVA) levels, which have been used to study the role of central dopamine in schizophrenia, and the positive/negative syndrome in first episode schizophrenic patients before and after antipsychotic treatment. Forty neuroleptic-naive first episode schizophrenic patients were monitored at baseline and on days 7, 14 and 28. Clinical status was evaluated with the Scale for the Assessment of Positive Symptoms (SAPS), the Scale for the Assessment of Negative Symptoms (SANS), and the Brief Psychotic Rating Scale. Plasma HVA levels were also measured. Patients were divided into predominantly positive or negative syndrome groups by subtracting SAPS from SANS scores, at baseline. A healthy control group was also enrolled. Schizophrenic patients as a group had significantly higher pHVA levels than controls at baseline (20.50+/-11.85 vs. 13.04+/-7.22 ng/ml). Moreover, 12 predominantly negative syndrome patients had similar mean baseline pHVA levels (21.30+/-12.36 ng/ml) to those of 28 predominantly positive syndrome patients (19.40+/-11.33 ng/ml). During follow-up, there was a different evolution of pHVA levels in the predominantly positive syndrome group than in the predominantly negative syndrome group, with a significantly greater global reduction of pHVA levels in the former. Although both groups showed clinical improvement following 4 weeks of treatment with risperidone, pHVA levels at endpoint were lower (13.29+/-5.91 ng/ml) than at baseline in patients in the predominantly positive syndrome group, while among those in the predominantly negative syndrome group there was no difference in pHVA levels before and after treatment (21.02+/-13.06 ng/ml). The different pHVA level profiles observed in predominantly positive and negative syndrome first episode patients after 4 weeks of treatment with risperidone suggest that each syndrome may have a different underlying neurobiology.

Does reactivity to stress cosegregate with subclinical psychosis? A general population twin study

OBJECTIVE

This study assessed the relationship between stress reactivity (trait 1) and psychosis (trait 2) across genetically related persons (cross-twin, cross-trait design) to examine whether stress reactivity is an uncontaminated and unconfounded familial marker of psychosis risk.

METHOD

Reactivity to stress and subclinical psychotic experiences were assessed in 289 female, general population twin-pairs. Cross-trait, within-twin associations investigating the association between stress reactivity and subclinical psychotic experiences in each person, were calculated. In addition, cross-trait, cross-twin associations were calculated to assess whether stress reactivity in one twin was moderated by subclinical psychotic experiences in the co-twin.

RESULTS

Cross-trait, within-twin analyses showed significant associations between stress reactivity and subclinical psychotic experiences in each person. In addition, the cross-trait cross-twin analyses showed that stress reactivity in twin 1 was significantly moderated by subclinical experiences in the co-twin.

CONCLUSION

The results suggest that the psychosis phenotype cosegregates with increased emotional reactivity to stress in daily life.

The relationship between dysphoria and proneness to hallucination and delusions among young adults

Previous research suggests that measures of dysphoria relate to positive schizophrenic symptoms. These relationships have rarely been studied within the dimensionality of psychopathology framework. The present study examined the relationship between 3 distinct aspects of dysphoria (depression and state and trait anxiety) and delusion and hallucination proneness in a nonclinical sample of young adults. A total of 472 participants were assessed on measures of dysphoria and delusion and hallucination proneness. Correlation analyses revealed significant associations between both anxiety and depression and hallucination and delusion proneness, suggesting that the association between dysphoria and positive symptoms is also present at a nonclinical level. Partial correlations, and hierarchical regression models, suggest an independent contribution of depression, over anxiety, in influencing hallucination and delusional proneness. The results are discussed in the framework of the cognitive account of schizophrenia and the dimensional model of psychopathology.

Correlation and familial aggregation of dimensions of psychosis in affected sibling pairs from China

BACKGROUND

A number of studies with conflicting results have examined the familiality of schizophrenia syndromes in Western populations.

AIMS

The objective of this study was to determine, using clinical data from concordant sibling pairs, whether symptom dimensions and other clinical characteristics of schizophrenia show familial aggregation and are therefore potentially useful traits in genetic studies.

METHOD

We measured clinical and demographic features, and symptom dimensions of schizophrenia in 137 families from China who had two or more affected members with schizophrenia. Within-sibling pair correlation was assessed with intraclass correlation coefficient and kappa statistics.

RESULTS

Global functioning, positive, disorganisation and dysphoric symptoms, premorbid schizotypal and schizoid traits, premorbid social adjustment, type and age at illness onset all showed significant evidence of familial aggregation. DSM-IV schizophrenia subtypes were also found to be familial.

CONCLUSIONS

This is the first study in a large non-European population to confirm that schizophrenia dimensions and clinical characteristics show significant familiality, implying possible heritability. This supports their use in the delineation of homogeneous subsets for future genetic studies.

Ethical questions in human clinical psychopharmacology: should the focus be on placebo administration?

Of all ethical issues in clinical trial designs, only placebo use is dealt with acrimony and unwarranted, rhetoric emphasis. Many misconceptions are biased and may hamper research in the mechanisms of healing and recovery if placebo is banned from clinical trials, as some influential ethicists propose. Current treatments in psychiatry are by no means optimal and may vary in their effect across studies, rendering difficult to find the best available therapeutic method with which to compare new drugs. Because drugs possess specific mechanisms, it is not possible to compare drugs with different mechanisms as to their relevance in the pathophysiology of a given disorder. Placebo acts through non-specific mechanisms and is the ideal control for any disorder whose pathophysiology is relatively unknown and its treatment is still suboptimal. Sticking to short-term patient benefit in a trial reflects an individualistically oriented thinking in contemporary ethics and is likely to limit further research and efforts to better understand the mechanisms of disease and drug action, but also those related to general body reactance and self-healing, which are enhanced by placebo administration. Because in history ethics are swinging between two opposed views, it is possible that in the near future, the balance will move towards communitarianism, which is more likely to better serve long-term patient needs. Ethicists should also consider some other aspects of human experimentation, such as the consistency of research lines and the trend to substitute older drugs with their metabolites or enantiomers.

Exophenotypical profile of adolescents with sustained attention deficit: A 10-year follow-up study

We aimed to explore prospectively the relationship between the presence of sustained attention deficit (SAD) in early adolescence and exophenotypical measures of vulnerability to schizophrenia spectrum disorders (personality and psychosocial measures) in early adulthood. Two cohorts of community adolescents were selected in 1993 according to the presence or absence of a CPT-linked SAD. In 2003, both cohorts (Index: n=42, and

CONTROL

n=38) were administered the O-LIFE, the SCID-II, the DOI battery and the COPE scale, among other tests. T-tests were used to compare both cohorts. Index subjects showed a higher level of negative schizotypy, avoidant, depressive and narcissistic personality traits, as well as more asocial behavior and poorer use of coping resources than CONTROL subjects did. A SAD in early adolescence may be associated with coping and social deficits, negative schizotypy, and personality traits indicative of emotional disturbance in adulthood. Our results suggest that SAD in early adolescence might be an indicator of psychopathology in adulthood and give support to dimensional models of psychopathology.

Dimensions and the psychosis phenotype

In this paper, we discuss the conceptual background for including a dimensional component to the DSM V diagnoses for psychoses. We review the evidence for a continuous distribution of psychosis like symptoms in the general population and summarise the research validating the clinical usefulness of psychopathological dimensions. We conclude that diagnostic models using both categorical and dimensional representations of psychosis have better predictive validity than either model independently. Dimensions do not appear to be diagnosis specific so a flexible scoring of dimensions across all psychotic and major affective disorders may be potentially more informative than a system where categorical diagnoses are kept artificially dimension-specific.

Four symptom dimensions in outpatients with schizophrenia

OBJECTIVE

The aim of this study was to assess the dimensional structure of the Positive and Negative Symptoms Scale (PANSS) to identify the psychopathological profiles of outpatients with schizophrenia.

METHOD

Two hundred and thirty-one persons with schizophrenia (DSM-IV criteria) were randomly selected from a register that included all patients under treatment in 5 mental health care centers in Spain. Patients were evaluated with a sociodemographic and clinical questionnaire, the PANSS, the Disability Assessment Scale short version, and the Global Assessment Functioning Scale. A principal component analysis with oblimin rotation was used to examine the factor structure of the PANSS. Different statistical analyses were done to compare the resulting factors with clinical, disability, and social functioning variables.

RESULTS

Mean age of patients included was 39.6 years and approximately 65% were male. Four principal components, each of them with eigenvalues greater than 1.5, accounted for 56.22% of the variance. After oblimin rotation, these factors were identified as the Negative (32.48%), Excitement (11.29%), Affective (7.45%), and Positive (5.01%) components. Significant positive correlation between age and the negative dimension was found. Also, we observed significant negative correlations between global assessment functioning and negative and positive dimensions. Total disability was significantly positively related to all dimensions.

CONCLUSION

Positive and negative dimensions are common in all principal component analysis results, but we also found affective and excitement dimensions. The present finding suggests that further investigation of symptom dimensions may help to improve symptom-specific treatments; future research should focus on the design of new treatment programs considering these results.

The relationships between symptom dimensions and dysphoria in schizophrenia

Previous studies have suggested that qualitatively distinct aspects of dysphoria (anxiety and depression) are related to specific dimension of schizophrenia symptomatology. Most of these studies used simple dimensions and dysphoria models, although finer distinctions could help defining specific relationships. This study examined the relationships of distinctive aspects of depression and anxiety (both state and trait) with symptom dimensions. Forty patients with a DSM-IV diagnosis of schizophrenia were assessed for symptoms (SAPS-SANS), trait and state anxiety (STAI) and depression (CDS). Symptoms ratings were summarized as dimensional scores according to a two-, three- or five-dimensional models proposed in the literature. The correlation analysis replicates previous observations that distinct aspects of dysphoria are associated with specific dimensions of schizophrenia, with the exception of disorganization. Moreover, controlling for intercorrelated variables revealed that schizophrenia and dysphoric symptoms might act in combination and/or through indirect links to contribute to illness expression. Our data further suggested that these associations may be best understood in terms of interactions between various processing biases alluded in the most recent cognitive accounts of schizophrenia symptoms.

Social cognitive problem-solving in schizophrenia: associations with fluency and verbal memory

This study assessed the relationship between social functioning and neurocognitive function in individuals with schizophrenia. Social cognitive problem-solving (SCPS) is a significant contributor to social competence and is an aspect of information processing that is involved in the identification and resolution of interpersonal or social problems. We examined 49 schizophrenia patients and 28 healthy controls using the means-ends problem-solving procedure (MEPS) for SCPS, the Rey Auditory Verbal Learning Test (RAVLT), the Wisconsin Card Sorting Test (WCST), and a series of fluency tests for neurocognitive assessment, as well as the Positive and Negative Syndrome Scale (PANSS) and the Global Assessment of Functioning (GAF). Fluency tests can be used to evaluate divergent thinking, and a qualitative analysis was done of the fluency test responses. The results suggest that patients with schizophrenia have a significantly poorer MEPS performance than normal controls. In patients with normal RAVLT scores, MEPS scores were correlated with task-modified responses on the fluency test but not with any of the WCST scores. This suggests that SCPS is related to divergent thinking that requires concept flexibility and/or the conversion of viewpoint in patients with schizophrenia in whom verbal memory function is preserved.

Changes in the neuropsychological correlates of clinical dimensions between the acute and stable phase of schizophrenia

This study was designed to investigate whether the neuropsychological correlates of the symptom dimensions of schizophrenia vary with the clinical state in patients followed from the acute to stable the phase of the illness. Fifteen patients were assessed for symptoms (SAPS-SANS) and undergone a complete neuropsychological assessment at two sessions. The first session (S1) was carried out within six days after admission, i.e., acute phase and the second (S2) at least two month after hospitalization, i.e., stable phase. The data were analyzed using stepwise regression models in which neuropsychological scores were in entered to predict each dimensional score. This analysis was applied on the S1 and S2 data as well as on the S2-S1 difference to assess the neuropsychological predictors of clinical changes. Generally, the results replicate the previous associations between neuropsychological and dimensional measures found in stable patients. In addition, this study shows if each dimension appears to rely on a key structure, symptom variations seems to involve changes in the spread of the dysfunction and/or changes in the connectivity between the key and other regions. The results also suggest that functional changes related to some symptoms dimensions occur to compensate for the dysfunction associated with other symptoms.

Secondary verbal memory: a potential endophenotype of schizophrenia

This study aimed at identifying neuropsychological endophenotypes of schizophrenia which met the criteria of stability and sensitivity. Twenty-six non-schizophrenic first-degree relatives together with their affected family members (all simplex-families) underwent assessment with a comprehensive neuropsychological test battery both at baseline and 13 months follow-up. Follow-up patients were in a state of stable remission. Further, 21 unrelated, demographically balanced, non-vulnerable controls were tested one at a time. A principal components analysis of our test battery resulted in four factors: (1) Vigilance, attention, and psychomotor, (2) secondary verbal memory, (3) immediate and working memory, and (3) abstraction and problem solving. At baseline testing our study revealed a pattern of selective cognitive deficits in the relative group that is less pronounced, yet qualitatively similar, to that found in the patient sample. The most severe deficits displayed both the patients and their relatives in the secondary verbal memory domain. The dysfunctions in secondary verbal memory at baseline testing significantly correlated with negative symptoms only. Secondary verbal memory deficits proved to be relatively independent of age at onset of illness, illness duration, and neuroleptic dosage. Longitudinally, dysfunctions in the patients' secondary verbal memory fluctuated over time and with negative symptoms, and persisted in remitted patients at the same level as in their relatives. In conclusion, the secondary verbal memory met the criteria of relative stability and sensitivity in our sample of simplex-families. Thus, the secondary verbal memory seems to be a potential endophenotypic marker of schizophrenia, even for cases with a hypothetically lower genetic loading.

DRD4 exon 3 variants are not associated with symptomatology of major psychoses in a German population

We previously reported an association of DRD4 exon 3 long alleles with delusional symptomatology, independently from psychiatric diagnoses [Am. J. Med. Genet. 105 (2001) 283; Psychiatry Res. 80 (1998) 129]. The aim of this investigation was to replicate these results in an independent sample from Germany. We studied 394 subjects, affected by bipolar disorder (n = 32), schizoaffective disorder (n = 45), and schizophrenia (n = 317). All affected subjects were evaluated using the Operational Criteria for Psychotic Illness (OPCRIT) checklist. DRD4 variants were not associated with symptomatology of major psychosis. Our present results, obtained in an independent German sample, did not confirm the association between DRD4 variants and delusional symptomatology. However it should be considered that the original sample included a much higher rate of mood disorders and this could partially explain the discrepancy.

Is our concept of schizophrenia influenced by Berkson's bias?

BACKGROUND

If both positive and negative dimensions of schizophrenia independently influence need for care, a higher estimate of the comorbidity between these dimensions is expected in clinical samples than would be the case if non-clinical cases were investigated (i.e. Berkson's bias). The present paper investigates whether positive and negative dimensions independently contribute to mental health care use in a general population sample.

METHOD

A prospective cohort study was conducted, in which 7076 individuals were interviewed with the Composite International Diagnostic Interview Schedule at baseline and 1 and 3 years later. Lifetime positive and negative psychotic experiences (PPE, NPE) were assessed at baseline. Mental health care use (MHC) was assessed at baseline, and prospectively 1 and 3 years later.

RESULTS

The rating of MHC was strongly associated with NPE and PPE, both retrospectively and prospectively and the effects of both variables remained strong and significant in the analyses with both variables included.

CONCLUSIONS

These results, therefore, suggest that the concept of schizophrenia, as a unitary entity with high comorbidity between positive and negative dimensions, is in part the result of Berkson's bias.

Should CBT Target the Social Impairments Associated With Schizophrenia?

Adjunctive cognitive behavior therapy (CBT) has been found to reduce the impact of symptoms among individuals with schizophrenia; however, CBT has not been used to address the social deficits in this clinical population. The current article elaborates the rationale for targeting social functioning with CBT. These reasons include the following: (a) Social dysfunction is a core feature of schizophrenia that is not directly improved with medication; (b) Improved social functioning is a treatment goal of many patients with schizophrenia, and thus treatments designed to improve social functioning may increase treatment motivation and reduce attrition; (c) Adaptive social functioning is a critical component of mental and physical health; and (d) Social dysfunction appears to be responsive to psychosocial intervention. This article concludes with a description of functional cognitive behavior therapy (FCBT), a CBT intervention that has been developed with enhanced focus on social impairments.

Dimensions of major psychoses: a confirmatory factor analysis of six competing models

The symptoms of major psychosis aggregate in factors. Models of one to eight dimensions have been reported. In the present study, we tested six competing factor models, based on the psychotic and affective items of the OPCRIT checklist, in a large sample (N = 1294) of patients diagnosed with DSM-IV schizophrenia (n = 460), bipolar disorder (n = 726) and delusional disorder (n = 108). Confirmatory factor analysis was used to test the following models: (1) unique psychotic dimension; (2) positive-manic items, negative-depressive items; (3) model 2 with the addition of a disorganized factor; (4A) positive, negative, depressive and manic dimensions; (4B) model 4A with loss of pleasure (Anhedonia) and loss of energy (Apathy) included among depressive instead of negative symptoms; and (5) same as model 4B except for the addition of a disorganized domain. The four- and five-factor models fit the data much better than simpler ones. Between the two four-factor models, M4B emerged as more appropriate than M4A. The five-factor solution (M5) displayed the best fit. In conclusion, our confirmatory factor analysis in a large sample of psychotic subjects indicated that the symptomatology of major psychoses is composed of the following five factors: mania, positive symptoms, disorganization, depression and negative symptoms.

Influence of depressive symptoms and premorbid adjustment on factor structure of phenomenology of schizophrenia: a study from India

This study investigated the nature of factor structure of schizophrenia syndromes using a sample of 151 patients with schizophrenia according to DSM-IV. The patients were assessed on the Scale for the Assessment of Positive Symptoms (SAPS), the Scale for the Assessment of Negative Symptoms (SANS), Hamilton Depression Rating Scale (HDRS) and the Phillips Rating Scale of Premorbid Adjustment in schizophrenia. Three factors-negative syndrome, reality-distortion syndrome and disorganized syndrome were extracted when only SAPS and SANS were analysed. Addition of the Phillips Rating Scale scores to SAPS and SANS ratings in the factorial equation led to splitting of the negative syndrome though reality-distortion and disorganized syndromes remained stable. Factor analysis of the HDRS scores with SAPS and SANS ratings resulted in the HDRS loading highly on reality-distortion syndrome and splitting of negative syndrome. Factor analysis of all the variables taken together resulted in delineation of four factors. The study suggests a link between depression and reality distortion. Apathy and anhedonia seem to be linked to premorbid adjustment.

The dimensional symptom structure of schizophrenia and its association with temperament and character

Recent studies suggest that personality may influence symptom expression and social functioning in schizophrenia. This study investigated the relationships between personality and symptom dimensions in schizophrenia patients. Fifty-two schizophrenia patients and 25 five healthy subjects were assessed using the Temperament and Character Inventory (TCI). The patients were also assessed for positive and negative symptoms using SAPS and SANS and scored according to Andreasen's (1995: Andreasen, N.C., Arndt, S., Alliger, R., Miller, D., Flaum, M. 1995. Symptoms of schizophrenia. Methods, meanings, and mechanisms. Arch. Gen. Psychiatry, 52, 341-351) classical three dimensional model and by the five dimensional model of Toomey et al. (1997: Toomey, R., Kremen, W.S., Simpson J.C., Samson, J.A., Seidman, L.J., Lyons, M.J., Faraone, S.V., Tsuang, M.T. 1997. Revisiting the factor structure for positive and negative symptoms: evidence from a large heterogeneous group of psychiatric patients. Am. J. Psychiatry, 154, 371-377). Comparisons between patients and controls revealed significant differences on various TCI scores consistent with a global disorganization of personality in schizophrenia involving both basic neurophysiological and potentially genetically determined traits (i.e. temperament) and developmental aspects of personality (i.e. character). Correlation analysis showed distinct associations between symptoms and personality dimensions. The results suggest that the negative and disorganized dimensions of schizophrenia are related temperamental factors, whereas the psychotic symptoms are more related to characterological abnormalities. The observed patterns of associations also underline the heterogeneity of the classical negative and positive dimensions of schizophrenia.

Patterns of symptoms in neuroleptic-naive patients with schizophrenia and related psychotic disorders before and after treatment

A three-factor structure of schizophrenic symptoms has received considerable support, but there are no data on the factor structure of symptoms in neuroleptic-naive patients and how symptoms evolve after the inception of antipsychotic treatment. Seventy neuroleptic-naive patients with schizophrenia or related psychotic disorders were assessed with the Scales for the Assessment of Positive and Negative Symptoms before and after neuroleptic treatment. Ten global ratings of symptoms were subjected to factor analysis at the two time points and the factor solutions compared. A three-factor structure composed of psychotic, disorganization, and negative dimensions was found at the two assessment points. The negative and disorganization factors were highly correlated at each assessment and across assessments. While the symptom composition of the factors at the neuroleptic-naive assessment fitted that described in most previous studies, the composition of the negative and disorganization factors after neuroleptic treatment was somewhat different in that attention and inappropriate affect loaded on the negative factor instead of the disorganization factor. It is concluded that caution is warranted when using the three-factor model of schizophrenic symptoms as it may not be stable at different phases of the illness.

DRD4 exon 3 variants associated with delusional symptomatology in major psychoses: a study on 2,011 affected subjects

We previously reported an association of DRD4 exon3 long allele variants with delusional symptomatology independently from diagnoses. The aim of this investigation was to study DRD4 in major psychoses and to test the association in a larger sample. We studied 2,011 inpatients affected by bipolar disorder (n = 811), major depressive disorder (n = 635), schizophrenia (n = 419), delusional disorder (n = 104), psychotic disorder not otherwise specified (n = 42), and 601 healthy controls. A subsample of 1,264 patients were evaluated using the OPCRIT checklist and differences of symptomatology factor scores among genetic variants were assessed using one-way analysis of variance (ANOVA). DRD4 allele and genotype frequencies in bipolars, schizophrenics, delusionals, and psychotic NOS were not significantly different from controls; major depressives showed a trend toward an excess of DRD4*Short and DRD4*Short/Short variants versus controls. The ANOVA on factor scores in the whole subsample of 1,264 subjects showed a significant difference on delusion factor in allele analysis (P = 0.007), and in genotype one (P = 0.018), with DRD4*Long containing variants associated with severe symptomatology. The analysis in the replication subjects only (n = 803) showed a trend in the same direction, though not reaching the significance level. This analysis in an enlarged sample suggests that DRD4*Long alleles exert a small but significant influence on the delusional symptomatology in subjects affected by major psychoses.

Integrating psychopathological dimensions in functional psychoses: a hierarchical approach

Previous factor analysis studies of psychotic symptomatology have demonstrated three psychopathological dimensions: positive, negative and disorganization. However, few studies have analyzed non-schizophrenic samples and most use a syndrome-level of analysis or only schizophrenic symptom scales. This study examined how many dimensions underlie psychosis, and whether within psychosis there is a hierarchical organization of dimensions.A total of 660 inpatients with an acute psychotic episode were studied. Psychopathology was measured through a wide psychopathological assessment using the Manual for the Assessment and Documentation of Psychopathology (AMDP-system). Principal component factor analysis was carried out on 64 psychopathological symptoms scoring 1 or higher in at least 10% of the sample. A 15-factor solution was obtained which failed to depict a psychosis model on clinical and methodological grounds. Further predetermined factor analyses ranging from 1 to 15 factors were carried out to examine alternative factor solutions. A 10-dimensional model was the best model on clinical, statistical and conceptual grounds. Moreover, the examination of the 1 to 10 dimensional models allowed us to infer a hierarchical model of psychopathological dimensions, which can be represented in the frame of a tree-structure. The model permitted transitions between psychiatric categories and psychopathological dimensions, and it was able to integrate previous factor solutions with different numbers of resulting dimensions.The findings have implications for the design of future studies and for the hierarchical conceptualization of psychopathological dimensions.

How many and which are the psychopathological dimensions in schizophrenia? Issues influencing their ascertainment

During the last two decades, much effort has been made to precisely characterize the symptom dimensions of schizophrenia. A number of dimensional models have been proposed, the most popular of which has been a three-dimensional model consisting of psychotic, negative and disorganizational symptoms. This model, however, has been criticized as too simplistic, and more complex models have been proposed, although to date there has been no consensus as to the number and nature of dimensions necessary to account for the whole range of schizophrenic symptoms. In the present paper, the authors review the main methodological issues which have led to the current confusion about the number of dimensions underlying schizophrenic psychopathology. Among the main issues influencing the delimitation of dimensions are: statistical procedures for determining the number of factors, phase of the illness, level of analysis of symptoms (i.e., symptoms or groups of symptoms), and measurement instrument used. Studies analyzing either a broad range of symptoms or particular symptoms at a finer level have produced a rather complex picture of schizophrenic dimensions. There is evidence supporting the existence of eight major dimensions of psychopathology: psychosis, disorganization, negative, mania, depression, excitement, catatonia and lack of insight. The dimensional structure of symptoms becomes even more complex if one considers that these big dimensions can be further divided into more elementary components. A hierarchical approach for organizing the complex dimensional structure of schizophrenic symptoms is proposed.

A prospective longitudinal 10-year study of schizophrenia's three major factors and depression

This study investigated the nature, independence, and stability of schizophrenia's syndrome factors and depression at 2, 4.5, 7.5 and 10 years post-index hospitalization. At the four follow-ups, 71 patients (48 with schizophrenia and 23 with schizoaffective disorder) were assessed for symptoms hypothesized to constitute the reality distortion, disorganized, and negative factors of schizophrenia. At the last three follow-ups, the patients were also assessed for symptoms of depression. Factor analyses of schizophrenia symptoms revealed more than three syndrome factors at each follow-up. Longitudinally, reality distortion was a stable and relatively independent factor. The negative syndrome was independent but was bifurcated into two dimensions, interpreted as social/emotional withdrawal and diminished movement/expressiveness. Although signs of disorganization were not unified or independent early in schizophrenia's course, speech/thought disorder, disorganized affect, and poverty of speech content coalesced to form a disorganization factor by the 7.5-year follow-up. When depressive symptoms were added to the analyses, depression constituted an independent and stable dimension of schizophrenia over time. Each schizophrenia factor demonstrated a unique longitudinal course. Courses included stable symptom consistency (reality distortion), evolving symptom convergence (disorganization), and recurrent bifurcation and symptom instability (the negative syndrome).

Clinical models of schizophrenia: a critical approach to competing conceptions

Clinical and etiopathological heterogeneity in schizophrenia has been recognized long ago. The main hypothesis held in this report is that as long as we are not able to disentangle the heterogeneity question at the clinical level, it is not likely that heterogeneity at the etiological and pathophysiological levels may be solved. While the description of symptoms and signs of schizophrenia has remained mainly unchanged over the years, the way in which authors have articulated the varied phenomenological manifestations has been very unequal, thus rendering different views of schizophrenia across periods and countries. We still lack a global and comprehensive model to understand clinical heterogeneity in schizophrenia. In absence of compelling evidence for supporting either a categorical or a dimensional view, it is necessary to integrate and empirically compare competing approaches. The use of a polydiagnostic approach on the one hand, and a multidimensional approach on the other (the polydiagnostic-multidimensional paradigm), seems to be a promising strategy to better understand the heterogeneity of schizophrenia.

Assessing quality in decision analytic cost-effectiveness models. A suggested framework and example of application

Despite the growing use of decision analytic modelling in cost-effectiveness analysis, there is a relatively small literature on what constitutes good practice in decision analysis. The aim of this paper is to consider the concept of 'validity' and 'quality' in this area of evaluation, and to suggest a framework by which quality can be demonstrated on the part of the analyst and assessed by the reviewer and user. The paper begins by considering the purpose of cost-effectiveness models and argues that the their role is to identify optimum treatment decisions in the context of uncertainty about future states of the world. The issue of whether such models can be defined as 'scientific' is considered. The notion that decision analysis undertaken at time t can only be considered scientific if its outputs closely predict the results of a trial undertaken at time t + 1 is rejected as this ignores the need to make decisions on the basis of currently available evidence. Rather, the scientific characteristic of decision models is based on the fact that, in principle at least, such analyses can be falsified by comparison of two states of the world, one where resource allocation decisions are based on formal decision analysis and the other where such decisions are not. This section of the paper also rejects the idea of exact codification of scientific method in general, and of decision analysis in particular, as this risks rejecting potentially valuable models, may discourage the development of novel methods and can distort research priorities. However, the paper argues that it is both possible and necessary to develop a framework for assessing quality in decision models. Building on earlier work, various dimensions of quality in decision modelling are considered: model structure (disease states, options, time horizon and cycle length); data (identification, incorporation, handling uncertainty); and consistency (internal and external). Within this taxonomy a (nonexhaustive) list of questions about quality is suggested which are illustrated by their application to a specific published model. The paper argues that such a framework can never be prescriptive about every aspect of decision modelling. Rather, it should encourage the analyst to provide an explicit and comprehensive justification of their methods, and allow the user of the model to make an informed judgment about the relevance, coherence and usefulness of the analysis.

Dopamine receptor D2 Ser/Cys 311 variant is associated with delusion and disorganization symptomatology in major psychoses

The D2 receptor (DRD2) is a binding site of many psychoactive drugs and it has been proposed as a genetic risk factor for psychiatric disorders. The aim of this investigation was to study the DRD2 S311C variant in major psychoses. We studied 1182 inpatients with diagnoses of bipolar disorder (n = 480), major depressive disorder (n = 269), schizophrenia (n = 366), delusional disorder (n = 44), psychotic disorder not otherwise specified (n = 23) and 267 healthy controls. Eight hundred and eighty-seven subjects were also scored for their lifetime symptomatology using the the Operational Criteria checklist for psychotic illness (OPCRIT). DRD2 variants were not associated with affected subjects even when possible confounders like gender and onset were considered. When we considered the 887 subjects with the symptomatologic analysis, we observed a significant association of the DRD2 S311C variant with both delusion and disorganization features. The association was present independently from diagnoses. Our results do not show that coding variants of the DRD2 S311C play a major role in conferring susceptibility to major psychoses, but they may be connected with disorganized and delusional symptomatology independently from diagnoses.

Serotonin-2C and serotonin-1A receptor genes are not associated with psychotic symptomatology of mood disorders

The serotonergic system is involved in both pathophysiology and treatment of mood disorders. In the present study we investigated the possible influence of the polymorphisms of the serotonin-1A and 2C receptor genes on the symptomatology of mood disorders. Eighty-four inpatients affected by mood disorders (72 bipolar and 12 major depressive disorder) were assessed by the Operational Criteria Checklist for Psychotic Illness to score their lifetime psychotic symptomatology. The subjects were also typed for 5HT1A and 5HT2C variants using polymerase chain reaction techniques. No association was found between 5HT2C and psychopathology as defined by the four symptomatologic factors used as phenotype definition (mania, depression, delusion, and disorganization) even when bipolar subjects were analyzed separately. Only one subject with the 5HT1A variant was observed. Genetic variation at the 5HT1A and 5HT2C receptor genes does not, therefore, play a major role in the pathogenesis of mood disorders symptomatology. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:161-166, 2000.

Impairment in test performance and symptom dimensions of schizophrenia

Schizophrenic patients were rated on three syndromal dimensions derived from positive and negative symptom ratings. Scores on each dimension were compared to performance on neuropsychological tests before and after coaching instructions. Patients evidenced significant improvement in performance on all measures readministered immediately after instruction. Disorganization symptoms were correlated with lower levels of performance on all pre-coaching, trial 1 tests. Disorganization symptoms were also associated with lower levels of trial 2 post-coaching performance, independent of pre-coaching scores. These results suggest that, within a population of schizophrenic patients, symptoms of disorganization are associated with relatively greater impairments in performance on neuropsychological tests and with impaired ability to improve test performance following coaching instructions. The three symptom dimensions show promise for reducing heterogeneity within samples of schizophrenic patients.

No association between serotonin-2A receptor gene polymorphism and psychotic symptomatology of mood disorders

Abnormalities of the serotonergic system are involved in the pathophysiology of mood disorders. In the present study, we investigated the possible influence of the T102C polymorphism of the serotonin-2A receptor gene (5-HT2A, 13q14-21) on the symptomatology of mood disorders. Inpatients affected by mood disorders (n = 246, 149 bipolar, 97 major depressive disorder) were assessed with a checklist of operational criteria for psychotic illness (OPCRIT) to score their lifetime psychotic symptomatology. The subjects were also typed for 5-HT2A variants using polymerase chain reaction techniques. No association was found between this polymorphism and psychopathology as defined by the four symptomatologic factors used in phenotype definition (mania, depression, delusion and disorganization). Genetic variation at the 5-HT2A receptor gene does not, therefore, appear to play a major role in the pathogenesis of major mood disorders.

Serotonin transporter gene not associated with psychotic symptomatology of mood disorders

A functional polymorphism in the upstream regulatory region of the serotonin transporter gene (5-HTTLPR) has been recently reported to be associated with mood disorders. In the present study we investigated the possible influence of 5-HTTLPR on the symptomatology of mood disorders. Two hundred and thirty inpatients affected by mood disorders (160 bipolar and 70 major depressive disorder) were assessed by the Operational Criteria checklist for psychotic illness (OPCRIT) and were also typed for the 5-HTTLPR variants using PCR techniques. Mania, Depression, Delusion and Disorganization were the four symptomatologic factors used as phenotype definition. 5-HTTLPR variants were not associated with these symptomatologic factors, and consideration of possible stratification effects, such as sex, age of onset and polarity, did not reveal any association either. The serotonin transporter gene does not, therefore, appear to be associated with the symptomatology of mood disorders.

Is schizophrenic symptomatology independent of the phase of the illness?

The difference in symptomatology between the acute and post-acute phase of schizophrenia was examined in the present study using prospective and longitudinal assessment of 86 newly admitted schizophrenic patients. In the acute phase of illness, four symptom components emerged (negative symptoms, excited, delusional/hallucinatory, and thought disorder) and three components were evident (negative symptoms, mixed symptoms, and thought disorder) in the post-acute phase. The negative component in the post-acute phase had the same composition as that in the acute phase. The composition of thought disorder barely persisted over the phase of illness. These findings suggest that the negative symptom component is stable while the difference in the phase of illness has some effects on the symptom structure of schizophrenia.

Factor structure and clinical validity of competing models of positive symptoms in schizophrenia

BACKGROUND

The factor structure of four competing models of positive symptoms and their clinical validity was studied in a sample of 253 schizophrenia inpatients.

METHODS

The following models were tested using confirmatory factor analysis: a one-dimension severity model, a two-dimension model comprising a psychosis factor and a disorganization factor, a four-dimension model based on the Scale for the Assessment of Positive Symptoms (SAPS) structure in subscales, and a five-dimension model derived from the previous one by further differentiating Schneiderian delusions from non-Schneiderian ones.

RESULTS

More complex multifactorial models fit the data better than simpler models. The five-dimension model was the best adjusted (goodness of fit index = .844, nonnormed fit index = .812, normed fit index = .728). Whereas the one-dimension model did not display significant association with the clinical variables, multidimensional models were related to age at onset and illness severity. The two-dimension model captured well the clinical correlates of the more complex models.

CONCLUSION

None of the tested models showed good fit to the data. The one-dimension model displayed both poor factor validity and poor external validity; therefore, research relying on the SAPS total score may reach misleading conclusions.

Meta-analysis of symptom factors in schizophrenia

Factor and correlational analyses have been used to characterize symptom dimensions in schizophrenia, though they have yielded divergent models. This study used meta-analysis of published work to determine the number and composition of symptom dimensions. Principal components analysis of data from 10 empirical studies (pooled n = 896) yielded three factors, 'positive', 'negative' and 'conceptual disorganization'. The findings suggest that a three-factor solution is a relatively stable outcome of studies assessing these symptoms in chronic patients, and that some symptoms (alogia, attentional impairment) are less likely to load uniquely on a single factor.

The structure of schizophrenic symptoms: a meta-analytic confirmatory factor analysis

To quantitatively review all presently available evidence about the interrelations between positive and negative schizophrenic symptoms, we created an aggregate matrix of the intercorrelations among schizophrenic symptoms by combining data from 28 independent samples using meta-analytic procedures (net bivariate dfs ranging from 683 to 1657). Using confirmatory factor analyses, we then statistically compared four theoretically derived models of the structure of schizophrenic symptoms. Although a three-factor model (Liddle, 1987) best fit the data, results suggest that either more factors or different symptoms are required to account well for the latent structure underlying schizophrenic symptomatology. The nature of such augmented approaches, the opportunities and constraints inherent to multifactorial models, and the limitations of current instruments are discussed.

Predicting schizophrenic outpatients' behavior by symptomatology and social skills

Though social skills have been identified as an independent construct, recent studies have revealed that schizophrenic symptomatology and social skills are interrelated. The nature and extent of this relationship, however, are far from clear. To address this issue, we examined 33 schizophrenic outpatients participating in a rehabilitation program for an average of 10 months. The object of this study was to investigate to what extent behavior can be predicted by symptomatology and social skills, and whether social skills have a significant effect on outpatients' behavior independently of schizophrenic symptoms and vice versa. Regression analyses revealed good prediction of outpatients' behavior by conceptual disorganization and disorder of relating from the PANSS and, to a lesser degree, social skills. After having eliminated the influence of psychopathology on social skills and behavior, social skills variables still had significant predictive value for social competence, social interest, and irritability. These findings imply specific contributions of both symptomatology and social skills to future behavior of chronic schizophrenic outpatients.

Symptom structure in schizophrenia: two-, three- or four-factor models?

Beside the syndromic dichotomy (negative-positive), other symptomatic dimensions have been described in schizophrenia. A question of interest is, therefore, to know which symptom structures can be individualized to characterize schizophrenia. Using confirmatory factor analysis in 135 patients, a two-factor model (negative-positive), a three-factor model (negative-positive-disorganization) and a four-factor model (negative-positive-disorganization-relational) were primarily identified with SANS (Scale for the Assessment of Negative Symptoms) and SAPS (Scale for the Assessment of Positive Symptoms). In contrast, no models could be identified with PANSS (Positive and Negative Syndrome Scale). The results confirm the relevance of other syndrome dimensions, beside the negative and positive ones and suggest that SANS-SAPS was more useful than PANSS in identifying an adequate dimensional factor structure of schizophrenic symptoms.

Factor structure of symptoms in functional psychoses

Global ratings from the Scale for the Assessment of Positive Symptoms and Scale for the Assessment of Negative Symptoms were subjected to principal-component analysis (PCA) in 80 schizophrenia patients, 76 patients with schizophreniform disorder, 80 patients with schizoaffective and mood disorders, and 78 patients with delusional, brief reactive, and atypical psychoses. The resulting factors were correlated with depressive, manic, and catatonic syndromes, and subjected to a multivariate analysis of variance across DSM-III-R diagnoses. PCAs revealed that psychosis, disorganization, and negative factors were also present in each of the nonschizophrenic groups. The disorganization factor tended to be related to the manic syndrome, and the negative factor to depressive and catatonic syndromes. Overall, the three factors had little diagnostic relevance in functional psychoses, although the negative factor was relatively more characteristic of schizophrenia. The data suggest that positive, negative, and disorganization factors are not specific to schizophrenia; this is consistent with a dimensional view of psychopathology in functional psychoses.