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

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.

Development and validation of the DISCUS scale: A reliable short measure for assessing experienced discrimination in people with mental health problems on a global level

BACKGROUND

The Discrimination and Stigma Scale (DISC-12) was specifically developed to measure experienced and anticipated discrimination reported by people with mental health problems. However, the length of the DISC-12 may represent a disadvantage especially in country settings with limited human capacity and infrastructure. The purpose of the study was to develop a short version of DISC-12 (DISCUS) to address these limitations.

METHODS

Data from 1087 participants with major depressive disorder and 732 patients with schizophrenia were collected as part of two research network studies across 35 countries - Anti Stigma Programme European Network (ASPEN) and International Study of Discrimination and Stigma (INDIGO). We used a Meta Exploratory Factor Analysis (meta-EFA) and a Multiple Causes Multiple Indicators (MIMIC) Model to reduce the number of items in the DISC-12 scale. The validity and reliability of the reduced scale (DISCUS) was tested in 202 people with the full spectrum of mental disorders recruited in a cross-sectional study conducted in South London. Psychometric validation for the reduced scale used confirmatory factor analysis and measures of Cronbach's alpha and Pearson's correlation coefficient.

RESULTS

meta-EFA reduced twenty-one items to twelve items. An additional item was discarded with the use of the MIMIC model. The 11-item DISCUS demonstrated excellent reliability (Cronbach's alpha >0.85), good fit (Tucker Lewis Index and Comparative Fit Index value>0.9) and weak to moderate construct validity.

CONCLUSIONS

The DISCUS scale is a consistent and valid instrument to measure experienced and anticipated discrimination predominantly in personal and social relationships in global settings.

Saccadic eye movements in different dimensions of schizophrenia and in clinical high-risk state for psychosis

BACKGROUND

Oculomotor dysfunction is one of the most replicated findings in schizophrenia. However the association between saccadic abnormalities and particular clinical syndromes remains unclear. The assessment of saccadic movements in schizophrenia patients as well as in clinical high-risk state for psychosis individuals (CHR) as a part of schizophrenia continuum may be useful in validation of saccadic movements as a possible biomarker.

METHODS

The study included 156 patients who met the ICD-10 criteria for schizophrenia: 42 individuals at clinical high-risk-state for psychosis and 61 healthy controls. The schizophrenia patients had three subgroups based on the sum of the global SAPS and SANS scores: (1) patients with predominantly negative symptoms (NS, n = 62); (2) patients with predominantly positive symptoms (PS, n = 54) (3) patients with predominantly disorganization symptoms (DS, n = 40). CHR subjects were characterized by the presence of one of the groups of criteria: (1) Ultra High Risk criteria, (2) Basic Symptoms criteria or (3) negative symptoms and formal thought disorders. Horizontal eye movements were recorded by using videonystagmograph. We measured peak velocity, latency and accuracy in prosaccade, antisaccade and predictive saccade tasks as well as error rates in the antisaccade task.

RESULTS

Schizophrenia patients performed worse than controls in predictive, reflexive and antisaccade tasks. Oculomotor parameters of NS were different from the other groups of patients. Latencies of predictive and reflexive saccades were significantly longer than in controls only in the NS group. The accuracy of predictive saccades was also different from controls only in the NS schizophrenia group. More prominent loss of accuracy of reflexive saccades was found in the DS group and it significantly differed from the one in other groups. Participants from DS group made more errors in antisaccade task compared to NS and PS groups. CHR subjects performed worse than controls as measured by the accuracy of reflexive saccades and antisaccades.

CONCLUSIONS

The study confirms the existence of different relations between the symptom dimensions of schizophrenia and saccades tasks performances. Saccadic abnormalities were revealed in the clinical (schizophrenia) and pre-clinical (clinical high risk) populations that provide further evidence for assessing saccadic abnormalities as a possible neurobiological marker for schizophrenia.

The component structure of the scales for the assessment of positive and negative symptoms in first-episode psychosis and its dependence on variations in analytic methods

A secondary analysis was undertaken on Scales for the Assessment of Positive and Negative Symptoms (SAPS/SANS) data from 345 first-episode psychosis (FEP) patients gathered in the West London FEP study. The purpose of this study was to determine: (i) the component structure of these measures in FEP (primary analyses), and (ii) the dependence of any findings in these primary analyses on variations in analytic methods. Symptom ratings were exposed to data reduction methods and the effects of the following manipulations ascertained: (i) level of analysis (individual symptom vs. global symptom severity ratings), (ii) extraction method (principal component vs. exploratory factor analysis) and (iii) retention method (scree test vs. Kaiser criterion). Whilst global ratings level analysis rendered the classic triad of psychotic syndromes (positive, negative and disorganisation), symptom level analyses revealed a hierarchical structure, with 11 first-order components subsumed by three second-order components, which also mapped on to this syndrome triad. These results were robust across data reduction but not component retention methods, suggesting that discrepancies in the literature regarding the component structure of the SAPS/SANS partly reflect the level of analysis and component retention method used. Further, they support a hierarchical symptom model, the implications of which are discussed.

Dietary patterns and respiratory health in adults from nine European countries-Evidence from the GA2 LEN study

BACKGROUND

Dietary patterns defined using principal component analysis (PCA) offer an alternative to the analysis of individual foods and nutrients and have been linked with asthma and allergic disease. However, results have not been reproducible in different settings.

OBJECTIVE

To identify dietary patterns common to different European countries and examine their associations with asthma and allergic symptoms.

METHODS

In sixteen study centers in nine European countries, 3206 individuals aged 15-77 years completed a common, internationally validated, food frequency questionnaire and a respiratory symptoms questionnaire. The outcomes of interest were current asthma, asthma symptoms score (derived based on responses to 5 asthma symptom-related questions), atopy (positive skin prick test). Spirometry was used to estimate forced expiratory volume in 1 second (FEV₁ ), forced vital capacity (FVC), the FEV₁ /FVC, spirometric restriction (FVC below the lower limit of normal (<LLN)) and FEV₁ /FVC < LLN. A novel meta-analytic approach was used to identify dietary patterns using PCA and to examine associations with asthma and allergic symptoms.

RESULTS

Two dietary patterns emerged, generally correlating with the same foods in different countries: one associated with intake of animal proteins and carbohydrates; the other with fruit and vegetables. There was evidence that the former pattern was associated with a higher asthma score (RR 1.63, 95% CI: 1.33-2.01), current asthma (RR 2.03, 95% CI: 1.52-2.71), wheeze (RR 1.84, 95% CI: 1.30-2.60), atopic status (RR 1.68, 95% CI: 1.16-2.44) and with decreased lung function, including an FVC <LLN (RR 4.57, 95% CI: 2.27-9.21).

CONCLUSIONS AND CLINICAL RELEVANCE

Our findings suggest an increase in sensitisation to common allergens, an increase in asthma symptoms, and a reduction in lung function in those eating a diet rich in animal proteins and carbohydrates. We found little evidence of an association between these outcomes and eating a diet rich in fruits and vegetables.

Validating dimensions of psychosis symptomatology: Neural correlates and 20-year outcomes

Heterogeneity of psychosis presents significant challenges for classification. Between 2 and 12 symptom dimensions have been proposed, and consensus is lacking. The present study sought to identify uniquely informative models by comparing the validity of these alternatives. An epidemiologic cohort of 628 first-admission inpatients with psychosis was interviewed 6 times over 2 decades and completed an electrophysiological assessment of error processing at year 20. We first analyzed a comprehensive set of 49 symptoms rated by interviewers at baseline, progressively extracting from 1 to 12 factors. Next, we compared the ability of resulting factor solutions to (a) account for concurrent neural dysfunction and (b) predict 20-year role, social, residential, and global functioning, and life satisfaction. A four-factor model showed incremental validity with all outcomes, and more complex models did not improve explanatory power. The 4 dimensions-reality distortion, disorganization, inexpressivity, and apathy/asociality-were replicable in 5 follow-ups, internally consistent, stable across assessments, and showed strong discriminant validity. These results reaffirm the value of separating disorganization and reality distortion, are consistent with recent findings distinguishing inexpressivity and apathy/asociality, and suggest that these 4 dimensions are fundamental to understanding neural abnormalities and long-term outcomes in psychosis. (PsycINFO Database Record

Early onset first episode psychosis: dimensional structure of symptoms, clinical subtypes and related neurodevelopmental markers

Despite the growing interest in a dimensional approach to the assessment of symptoms and clinically relevant phenomena in schizophrenia spectrum disorders, very few studies, to date, have examined the dimensional structure of symptoms in early onset first episode psychosis. In the present study, we assessed a sample of 60 children and adolescents of both sexes with first episode schizophrenia spectrum psychosis. A principal component analysis (PCA) of the Positive and Negative Syndrome Scale (PANSS) was performed and the factors obtained were used to carry out a cluster analysis. Sex, age of onset before or after 13, markers of early neurodevelopmental impairment and intellectual disabilities were considered as variables to characterized potential clinical subtypes, applying a one-way analysis of variance. Four factors were extracted ("negative symptoms", "delusions", "conceptual disorganization" and "paranoid/hostility"), each of them identifying a discrete clinical subtype of patients. No difference was found among the groups about sex and age of onset; delayed speech/language development was significantly associated with the "delusions" subtype and both "conceptual disorganization" and "delusions" subtypes showed a lower intelligence quotient (IQ). The four factors model we presented highlights "negative symptoms" as the most consistent factor; among positive symptoms, unusual thought content and conceptual disorganization resulted more distinctive of psychosis, at this age range, than perceptual abnormalities. Evolutionary trajectories of the four clinical subtypes we obtained seem to be influenced by cognitive and neurodevelopmental impairment rather than sex and age of onset.

Individual negative symptoms and domains - Relevance for assessment, pathomechanisms and treatment

The negative symptoms of schizophrenia can be divided into two domains. Avolition/apathy includes the individual symptoms of avolition, asociality and anhedonia. Diminished expression includes blunted affect and alogia. Until now, causes and treatment of negative symptoms have remained a major challenge, which is partially related to the focus on negative symptoms as a broad entity. Here, we propose that negative symptoms may become more tractable when the different domains and individual symptoms are taken into account. There is now increasing evidence that the relationship with clinical variables - in particular outcome - differs between the domains of avolition/apathy and diminished expression. Regarding models of negative symptom formation, those relevant to avolition/apathy are now converging on processes underlying goal-directed behavior and dysfunctions of the reward system. In contrast, models of the diminished expression domains are only beginning to emerge. The aim of this article is to review the specific clinical, behavioral and neural correlates of individual symptoms and domains as a better understanding of these areas may facilitate specific treatment approaches.

Meta-analysis of the Brief Psychiatric Rating Scale - Expanded (BPRS-E) structure and arguments for a new version

The factor structure of the 24 item BPRS-E was examined to determine the effect of additional items on consensus scales derived primarily from the 18 item BPRS. A meta-analysis (k = 32, n = 10,084) of previous factor analyses of the BPRS-E was conducted using both a co-occurrence similarity matrix and reproduced correlations. Components generally supporting the consensus scales were found suggesting four relatively invariant subscales: Affect (defined by the core items: anxiety, guilt, depression, suicidality), Positive Symptoms (hallucinations, unusual thought content, suspiciousness, grandiosity), Negative Symptoms (blunted affect, emotional withdrawal, motor retardation) and Activation (excitement, motor hyperactivity, elevated mood, distractibility). The additional BPRS-E items primarily contribute directly to a clear Activation dimension which expands and clarifies the traditional 18 item BPRS structure. Though not statistically supported in this meta-analysis, a fifth factor describing disorganization (conceptual disorganization, disorientation, self-neglect, mannerisms-posturing) was present in some analyses and should be considered. The five factor solution including a disorganization factor has theoretical validity based on the pentagonal model of schizophrenia while also containing the same four primary dimensions that were statistically supported in this meta-analysis. A new version of the BPRS (BPRS-26) with modified and additional items is presented. BPRS-26 is supposed to enhance the stability and the comprehensiveness of the scale and to more closely measure this five factor model.

Factor Analysis in Counseling Psychology Research, Training, and Practice

Exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) have contributed to test development and validation in counseling psychology, but additional applications have not been fully realized. The author presents an overview of the goals, terminology, and procedures of factor analysis; reviews best practices for extracting, retaining, and rotating factors in EFA; describes issues related to CFA, including potential hypotheses, how parameters are estimated, and current guidelines regarding sample size and the use of fit indices; and reviews more sophisticated applications of CFA, including multiple-groups analysis and testing of hierarchical models. Finally, the author recommends how to increase the application of factor analysis to counseling psychologists’ work in research, training, and practice settings.

Symptom assessment in early psychosis: the use of well-established rating scales in clinical high-risk and recent-onset populations

Symptom assessment in early psychosis research typically relies on scales validated in chronic schizophrenia samples. Our goal was to inform investigators who are selecting symptom scales for early psychosis research. We described measure characteristics, baseline scores, and scale inter-relationships in clinical-high-risk (CHR) and recent-onset psychotic disorder (RO) samples using the Positive and Negative Syndrome Scale, Brief Psychiatric Rating Scale, Scale for the Assessment of Positive Symptoms, and Scale for the Assessment of Negative Symptoms; for the CHR group only, we included the Scale of Prodromal Symptoms. For investigators selecting symptom measures in intervention or longitudinal studies, we also examined the relationship of symptom scales with psychosocial functioning. In both samples, symptom subscales in the same domain, across measures, were moderately to highly intercorrelated. Within all measures, positive symptoms were not correlated with negative symptoms, but disorganized symptoms overlapped with both positive and negative symptoms. Functioning was significantly related to negative and disorganized, but not positive, symptoms in both samples on most measures. Findings suggest strong overlap in symptom severity ratings among the most common scales. In recent-onset samples, each has strengths and weaknesses. In CHR samples, they appear to add little information above and beyond the SOPS.

Facial emotion identification in early-onset psychosis

Facial emotion identification (FEI) deficits are common in patients with chronic schizophrenia and are strongly related to impaired functioning. The objectives of this study were to determine whether FEI deficits are present and emotion specific in people experiencing early-onset psychosis (EOP), and related to current clinical symptoms and functioning. Patients with EOP (n=34, mean age=14.11, 53% female) and healthy controls (HC, n=42, mean age 13.80, 51% female) completed a task of FEI that measured accuracy, error pattern and response time. Relative to HC, patients with EOP (i) had lower accuracy for identifying facial expressions of emotions, especially fear, anger and disgust, (ii) were more likely to misattribute other emotional expressions as fear or disgust, and (iii) were slower at accurately identifying all facial expressions. FEI accuracy was not related to clinical symptoms or current functioning. Deficits in FEI (especially for fear, anger and disgust) are evident in EOP. Our findings suggest that while emotion identification deficits may reflect a trait susceptibility marker, functional deficits may represent a sequelae of illness.

Cognitive-behavioural therapy for the symptoms of schizophrenia: systematic review and meta-analysis with examination of potential bias

BACKGROUND

Cognitive-behavioural therapy (CBT) is considered to be effective for the symptoms of schizophrenia. However, this view is based mainly on meta-analysis, whose findings can be influenced by failure to consider sources of bias.

AIMS

To conduct a systematic review and meta-analysis of the effectiveness of CBT for schizophrenic symptoms that includes an examination of potential sources of bias.

METHOD

Data were pooled from randomised trials providing end-of-study data on overall, positive and negative symptoms. The moderating effects of randomisation, masking of outcome assessments, incompleteness of outcome data and use of a control intervention were examined. Publication bias was also investigated.

RESULTS

Pooled effect sizes were -0.33 (95% CI -0.47 to -0.19) in 34 studies of overall symptoms, -0.25 (95% CI -0.37 to -0.13) in 33 studies of positive symptoms and -0.13 (95% CI -0.25 to -0.01) in 34 studies of negative symptoms. Masking significantly moderated effect size in the meta-analyses of overall symptoms (effect sizes -0.62 (95% CI -0.88 to -0.35) v. -0.15 (95% CI -0.27 to -0.03), P = 0.001) and positive symptoms (effect sizes -0.57 (95% CI -0.76 to -0.39) v. -0.08 (95% CI -0.18 to 0.03), P<0.001). Use of a control intervention did not moderate effect size in any of the analyses. There was no consistent evidence of publication bias across different analyses.

CONCLUSIONS

Cognitive-behavioural therapy has a therapeutic effect on schizophrenic symptoms in the 'small' range. This reduces further when sources of bias, particularly masking, are controlled for.

Categorical vs dimensional classifications of psychotic disorders

OBJECTIVE

Both categorical and dimensional methods appear relevant to classifying psychotic disorders; however, there is no clear consensus on the most appropriate categories and dimensions or on the best approach for constructing nosologic criteria that integrate these 2 methods. This review examines the evidence on specific dimensions and categories that would best characterize psychoses.

METHOD

Entries in the MEDLINE database between 1980 and 2011 were searched for studies of the dimensional and/or categorical structure of psychosis. Studies were included if samples represented a spectrum of psychotic disorders and dimensions/categories were empirically derived using principal components analysis, factor analysis, or latent class analysis.

RESULTS

Most dimensional studies observed 4 or 5 dimensions within psychosis, with positive, negative, disorganization, and affective symptom domains most frequently reported. Substance abuse, anxiety, early onset/developmental, insight, cognition, hostility, and behavioral/social disturbance dimensions appeared in some studies. Categorical studies suggested 3 to 7 major classes within psychosis, including a class similar to Kraepelin's dementia praecox and one or more classes with significant mood components. Only 2 studies compared the relative fit of empirically derived dimensions and categories within the same data set, and each had significant limitations.

CONCLUSION

There is relatively consistent evidence on appropriate categories and dimensions for characterizing psychoses. However, the lack of studies directly comparing or combining these approaches provides insufficient evidence for definitive conclusions about their relative merits and integration. The authors provide specific recommendations for designing future studies to identify valid dimensions and/or categories of the psychoses and investigate hybrid approaches to model the structure of the underlying illnesses.

Measuring patient-reported outcomes in psychosis: conceptual and methodological review

BACKGROUND

There are calls to use patient-reported outcomes (PROs) routinely across mental health services. However, the use of PROs in patients with psychosis has been questioned.

AIMS

To examine the concepts and measures of four widely used PROs: treatment satisfaction, subjective quality of life, needs for care and the quality of the therapeutic relationship.

METHOD

We conducted a literature search of academic databases on concepts, characteristics and psychometric properties of the four PROs in patients with psychosis.

RESULTS

Although numerous concepts and measures have been published, evidence on the methodological quality of existing PROs is limited. Measures designed to assess distinct PROs showed a considerable conceptual, operational and empirical overlap, and some of them also included specific aspects. The impact of symptoms and cognitive deficits appears unlikely to be of clinical significance.

CONCLUSIONS

The popularity of PROs has not been matched with progress in their conceptualisation and measurement. Based on current evidence, some recommendations can be made. Distinct and short measures with clinical relevance and sufficient psychometric properties should be preferred. Future research should optimise the validity and measurement precision of PROs, while reducing assessment burden.

The validity of subjective quality of life measures in psychotic patients with severe psychopathology and cognitive deficits: an item response model analysis

PURPOSE

Subjective quality of life (SQOL) is an established patient-reported outcome in the evaluation of treatments for psychosis. The use of SQOL measures in the presence of psychiatric symptoms and cognitive deficits has been questioned. However, there is little evidence on whether items function differently as indicators of SQOL in psychotic patients with different levels of symptoms and deficits. Substantial differential item functioning (DIF) would, indeed, challenge the validity of established measures. We aimed to investigate the validity of a widely used measure of subjective quality of life (SQOL), i.e., the Lancashire Quality of Life Profile (LQOLP), in the presence of cognitive deficits and psychiatric symptoms in patients with severe and enduring psychosis.

METHOD

We analysed SQOL ratings of 690 psychotic patients on the LQOLP using item response modelling to detect differential item functioning (DIF) attributable to psychiatric symptoms and cognitive deficits.

RESULTS

Patients with more severe general psychopathology were less likely to rate their 'personal safety' positively (OR .96, 95% CI .93-.99). More severely depressed patients were less likely to endorse positive 'life as a whole' (OR .93, 95% CI .89-.98) and 'mental health' (OR .93, 95% CI .91-.97) ratings. There was no DIF attributable to cognitive deficits.

CONCLUSIONS

The findings suggest that the validity of the LQOLP in psychotic patients may be impaired by DIF due to psychopathology, although the magnitude of effects is unlikely to be of clinical significance. The validity appears not to be compromised by cognitive deficits.

Striatal function in relation to negative symptoms in schizophrenia

BACKGROUND

Previous studies have suggested that motivational aspects of executive functioning, which may be disrupted in schizophrenia patients with negative symptoms, are mediated in part by the striatum. Negative symptoms have been linked to impaired recruitment of both the striatum and the dorsolateral prefrontal cortex (DLPFC). Here we tested the hypothesis that negative symptoms are associated primarily with striatal dysfunction, using functional magnetic resonance imaging (fMRI).

METHOD

Working-memory load-dependent activation and gray matter volumes of the striatum and DLPFC were measured using a region-of-interest (ROI) approach, in 147 schizophrenia patients and 160 healthy controls. In addition to testing for a linear relationships between striatal function and negative symptoms, we chose a second, categorical analytic strategy in which we compared three demographically and behaviorally matched subgroups: patients with a high burden of negative symptoms, patients with minimal negative symptoms, and healthy subjects.

RESULTS

There were no differences in striatal response magnitudes between schizophrenia patients and healthy controls, but right DLPFC activity was higher in patients than in controls. Negative symptoms were inversely associated with striatal, but not DLPFC, activity. In addition, patients with a high burden of negative symptoms exhibited significantly lower bilateral striatal, but not DLPFC, activation than schizophrenia patients with minimal negative symptoms. Working memory performance, antipsychotic exposure and changes in gray matter volumes did not account for these differences.

CONCLUSIONS

These data provide further evidence for a robust association between negative symptoms and diminished striatal activity. Future work will determine whether low striatal activity in schizophrenia patients could serve as a reliable biomarker for negative symptoms.

Heritability estimates for psychotic symptom dimensions in twins with psychotic disorders

Factor analysis of psychotic symptoms frequently results in positive, negative, and disorganized dimensions, but heritability estimates have not yet been reported. Symptom dimensions are usually only measured in individuals with psychotic disorders. Here, it is valuable to assess influences acting via liability to psychosis and independent modifying effects. We estimated heritability for psychotic symptom dimensions, taking account of these issues. Two-hundred-and-twenty-four probandwise twin pairs (106 monozygotic, 118 same-sex dizygotic), where probands had psychoses, were ascertained from the Maudsley Twin Register in London (1948-1993). Lifetime history of DSM-III-R psychotic disorder and psychotic symptom dimensions was assessed from clinical records and research interviews and rated using the Operational Criteria Checklist. Estimates of heritability and environmental components of variance in liability were made with structural equation modeling using a causal-contingent common pathway model adapted for ascertainment from a clinical register. Significant heritability was found for DSM-III-R psychotic disorder (h² = 90%, 95%CI 68-94%) and the disorganized symptom dimension (h² = 84%, 95%CI 18-93%). The heritability for the disorganized dimension remained significant when influences acting through liability to psychosis were set to zero, suggesting that some influences on disorganization are modifying factors independent of psychosis liability. However, the relative extent of modifying factors versus influences acting through psychosis liability could not be clearly determined. To our knowledge, this study provides the first formal evidence of substantive heritability for the disorganized symptom dimension, and suggests that genetic loci influencing disorganization in individuals with psychoses are in some cases different from loci that influence risk of psychotic disorders themselves.

The diagnostic concept of schizophrenia: its history, evolution, and future prospects

More than a century since the delineation of dementia praecox by Kraepelin, the etiology, neuropathology and pathophysiology of schizophrenia remain elusive. Despite the availability of criteria allowing reliable diagnostic identification, schizophrenia essentially remains a broad clinical syndrome defined by reported subjective experiences (symptoms), loss of function (behavioral impairments), and variable patterns of course. Research has identified a number of putative biological markers associated with the disorder, including neurocognitive dysfunction, brain dysmorphology, and neurochemical abnormalities. Yet none of these variables has to date been definitively proven to possess the sensitivity and specificity expected of a diagnostic test. Genetic linkage and association studies have targeted multiple candidate loci and genes, but failed to demonstrate that any specif ic gene variant, or a combination of genes, is either necessary or sufficient to cause schizophrenia. Thus, the existence of a specific brain disease underlying schizophrenia remains a hypothesis. Against a background of an ever-increasing volume of research data, the inconclusiveness of the search for causes of the disorder fuels doubts about the validity of the schizophrenia construct as presently defined. Given the protean nature of the symptoms of schizophrenia and the poor coherence of the clinical and biological findings, such doubts are not without reason. However, simply dismantling the concept is unlikely to result in an alternative model that would account for the host of clinical phenomena and research data consistent with a disease hypothesis of schizophrenia. For the time being, the clinical concept of schizophrenia is supported by empirical evidence that its multiple facets form a broad syndrome with non-negligible internal cohesion and a characteristic evolution over time. The dissection of the syndrome with the aid of endophenotypes is beginning to be perceived as a promising approach in schizophrenia genetics.

Dietary patterns and risk of asthma: results from three countries in European Community Respiratory Health Survey-II

Dietary patterns offer an alternative to the analysis of individual foods or nutrients in nutritional epidemiological studies. The aim of the present study was to identify dietary patterns common to different European countries and examine their associations with asthma. In five study centres (two in Germany, two in the UK and one in Norway), 1174 adults aged 29-55 years completed a FFQ and respiratory symptoms questionnaire. A meta-analytic approach was used to identify the dietary patterns and analyse them in relation to current asthma, asthma symptoms and bronchial responsiveness (BHR). Two patterns emerged, generally correlating with the same foods at different centres: one associated with intake of meats and potatoes; the other with fish, fruits and vegetables. There was no evidence that the fish, fruits and vegetables pattern was associated with asthma (OR 1.11 (95 % CI 0.93, 1.33)), symptom score (ratio of means 1.07 (0.98, 1.17)) or BHR (regression coefficient - 0.01 ( - 0.12, 0.10)), though these CI appeared to rule out large protective effects of consuming these foods. There was no overall evidence that the meat and potato pattern was associated with asthma (OR 1.02 (0.79, 1.31)), symptom score (ratio of means 1.07 (0.84, 1.36)) or BHR (regression coefficient - 0.08 ( - 0.27, 0.10)), but there was heterogeneity between centres in the association with symptom score: a negative association at the two German centres; a positive association at the others. Heterogeneity in a multi-centre observational study of diet could suggest alternative explanations for apparent effects of diet, such as uncontrolled confounding.

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.

The role of effort, cognitive expectancy appraisals and coping style in the maintenance of the negative symptoms of schizophrenia

The aim of the present study was to assess the role of psychological factors, specifically effort, coping, and negative expectancy appraisals, in addition to executive functioning and depression, in accounting for negative symptoms broadly defined. Fifty inpatients with acute schizophrenia participated in a study with a cross-sectional design. All of the psychological variables had significant partial correlations with some of the measures of negative symptoms when depression was controlled. A series of multiple regression analyses indicated that executive functioning only made a significant unique contribution to the prediction of affective flattening, whereas psychological factors made unique contributions to the variance in each of the negative symptom subscales apart from affective flattening, as well as to the negative symptom total score, accounting for 9% to 19% of the variance. These results suggest that, in addition to neuropsychological variables, psychological variables are important for understanding negative symptoms in acute schizophrenia.

Dimensions underlying outcome criteria in bipolar I disorder

OBJECTIVE

Various subjective and objective criteria are used to assess outcome in bipolar disorder. In this study, we explored to what extent they reflect distinct categories and whether underlying dimensions can be identified.

PATIENTS AND METHODS

One-hundred and twenty-one subjects with at least three episodes of bipolar I disorder (DSM-IV) were assessed on average 4.8 years after hospitalization. We assessed 14 variables reflecting different outcome criteria including subjective quality of life (SQOL), self-rated and observer-rated psychopathology, and functioning and disability. A principal component analysis was computed across all outcome variables. Identified dimensions were correlated with sociodemographic characteristics, illness history, premorbid adjustment and personality traits.

RESULTS

Three outcome dimensions were identified, i.e. a 'general subjective', a 'functioning/disability' and a 'manic/psychotic symptoms' dimension. Together they explain 69% of the total variance. The 'general subjective' dimension consists of SQOL scales and self-rated depressive symptoms. It is associated with comorbid anxiety disorders and personality disorders, high neuroticism and not having been in hospital in the last year. The 'functioning/disability' dimension comprises of criteria reflecting negative symptoms, disability and low functioning. It is associated with more prior illness episodes and low premorbid adjustment. The 'manic/psychotic symptoms' dimension consists of observer-rated manic and positive psychotic symptoms. It is correlated with not currently taking a specific medication.

LIMITATIONS

Cross-sectional design with a limited sample size.

CONCLUSION

The findings indicate that outcome criteria in bipolar I disorder can be grouped into three distinct dimensions reflecting (1) subjective appraisals, (2) functioning/disability and (3) manic/psychotic symptoms. While measurement of psychotic/manic symptoms has become a matter of course, until now few studies have assessed disability or subjective appraisal in bipolar illness. Therefore important aspects of bipolar illness might be overseen. For a better understanding, we suggest that longitudinal studies of bipolar I disorders should consider all three dimensions of outcome and measure them separately.

Subtyping schizophrenia: implications for genetic research

Phenotypic variability and likely extensive genetic heterogeneity have been confounding the search for the causes of schizophrenia since the inception of the diagnostic category. The inconsistent results of genetic linkage and association studies using the diagnostic category as the sole schizophrenia phenotype suggest that the current broad concept of schizophrenia does not demarcate a homogeneous disease entity. Approaches involving subtyping and stratification by covariates to reduce heterogeneity have been successful in the genetic study of other complex disorders, but rarely applied in schizophrenia research. This article reviews past and present attempts at delineating schizophrenia subtypes based on clinical features, statistically derived measures, putative genetic indicators, and intermediate phenotypes, highlighting the potential utility of multidomain neurocognitive endophenotypes.

The structure of negative symptoms within schizophrenia: implications for assessment

This review examines the structural validity of negative symptoms focusing on 2 questions: (1) Do negative symptoms represent a domain separate from other symptoms in schizophrenia? and (2) Within negative symptoms, is there a structure that suggests multidimensionality? Results from exploratory and confirmatory factor analytic studies are examined to address these questions. Across studies and symptom instruments, negative symptoms appear to consistently emerge as a factor separate from other dimensions of the illness in schizophrenia. Whether 2-, 3-, or 5-factor models are identified, negative symptoms consistently load on a factor separate from positive symptoms, affective symptoms of depression or anxiety, and symptoms of disorganization. Focusing on negative symptoms themselves, factor analytic findings suggest that this construct is multidimensional with at least 2 factors (involving diminished expression and anhedonia-asociality). Although these factors were replicable, serious limitations were noted in this literature. Thus, 2- (or even 3- or 5-) factor models of negative symptoms should not be considered definitive, but rather all converge to support the general conclusion of the multidimensionality of negative symptoms. The later findings indicate the importance of employing assessments that provide adequate coverage of the broad domain of negative symptoms. Importantly, caution is noted in the interpretability of findings based on existing instruments, and implications for future assessment are discussed.

Meta-analysis of the brief psychiatric rating scale factor structure

A meta-analysis (N=17,620; k=26) of factor analyses of the Brief Psychiatric Rating Scale (BPRS) was conducted. Analysis of the 12 items from Overall et al.'s (J. E. Overall, L. E. Hollister, & P. Pichot, 1974) 4 subscales found support for his 4 subscales. Analysis of all 18 BPRS items found 4 components similar to those of Overall et al. In a 5-component solution, a 5th activation component emerged but was best supported among samples of schizophrenic patients. The first 4 components appear to form the core of the BPRS factor structure. Results of the meta-analysis suggest 5 subscales (with items in parentheses): Affect (anxiety, guilt, depression, somatic); Positive Symptoms (thought content, conceptual disorganization, hallucinatory behavior, grandiosity); Negative Symptoms (blunted affect, emotional withdrawal, motor retardation); Resistance (hostility, uncooperativeness, suspiciousness); and Activation (excitement, tension, mannerisms-posturing).

Examining the latent structure of negative symptoms: is there a distinct subtype of negative symptom schizophrenia?

Negative symptoms have emerged as a replicable factor of symptomatology within schizophrenia. Although rating scales provide assessments along dimensions of severity, categorization into a negative symptom subtype is typically conducted. A categorical view of negative symptoms is best reflected in the proposal that enduring, primary negative symptoms, or deficit symptoms, reflect a distinct subtype of schizophrenia . Despite an accumulation of findings that support a categorical conceptualization, the data are also consistent with a dimensional-only model where negative symptom subtypologies simply reflect an extreme on a continuum of severity. Using taxometric statistical methods , the present study examined whether a taxonic, or latent class, model best describes negative symptoms in a sample of 238 schizophrenia patients. In order to obtain more stable estimates of symptoms, ratings on the Scale for the Assessment of Negative Symptoms [Andreasen, N.C., 1982. Negative symptoms in schizophrenia: Definition and reliability. Arch. Gen. Psychiatry 39, 784-788.] were averaged across two assessments over a 6-month period. Two taxometric methods, maximum covariance analysis (MAXCOV) and mean above minus below a cut (MAMBAC) identified a latent class or taxon with a base rate of approximately 28-36%. Members of the negative symptom taxon differed from the nontaxon class in that taxon members were more likely to be male and demonstrated poorer social functioning. Taxon and nontaxon schizophrenia patients did not differ in psychotic or affective symptoms. The findings converge to provide support for a categorical view of negative symptoms. Further research is required to replicate the present taxonic findings and to examine characteristics (including possible etiological factors) associated with this negative symptom taxon.

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.

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.

Testing a Four-Factor Model of Psychopathy and Its Association With Ethnicity, Gender, Intelligence, and Violence

Although a 2-factor model has advanced research on the psychopathy construct, a 3-factor model was recently developed that emphasized pathological personality and eliminated antisocial behavior. However, dropping antisocial behavior from the psychopathy construct may not be advantageous. Using a large sample of psychiatric patients from the MacArthur Risk Assessment Study (J. Monahan & H. J. Steadman, 1994), the authors used confirmatory factor analysis to test a 4-factor model of psychopathy, which included interpersonal, affective, and behavioral impulsivity dimensions and an antisocial behavior dimension. Model fit was good for this 4-factor model, even when ethnicity, gender, and intelligence variables were included in the model. Structural equation modeling was used to compare the 3- and 4-factor models in predicting proximal (violence) and distal (intelligence) correlates of psychopathy.

Meta-analysis of the factor structures of four depression questionnaires: Beck, CES-D, Hamilton, and Zung

Four separate metaanalyses of factor analyses were conducted for the Beck Depression Inventory (BDI), the Center for Epidemiological Studies Depression Scale (CES-D), the Hamilton Rating Scale for Depression (HRSD), and the Zung Self-Rating Depression Scale (SDS). The total number of participants (N) and studies (k) included in each of the metaanalyses were the following: BDI (N = 13,643, k = 33), CES-D (N = 22,340, k = 28), HRSD (N = 2,606, k = 17), and SDS (N = 12,621, k = 13). Metaanalysis results suggest that the specific depression symptom factors within each test appear to be relatively robust and well established and match fairly closely previously hypothesized factor structures. A general Depression Severity factor and a small Somatic Symptoms factor are found in all four tests and two tests had a small Positive Affect factor. There were fewer common specific depression symptom factors across tests than expected.

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.

Factor structure of paranoid schizophrenia: a prospective study

Paranoid schizophrenics were scored and analyzed using PANSS and principal component method on admission (T1, 480 patients), after 4 weeks (T2, 223 patients), after 8 weeks (T3, 146 patients) and after 6 months of treatment (T4, 104 patients). Seven factor models accounted for 68-74% of the variances (including models of 104 patients present at all four stages). T1 and T2 models comprised 6-7 factors and were dominated by positive and excitement symptoms. The grandiosity factor could only be identified in T1. T3 and T4 models were reduced to 5 factors and incorporated a greater expression of depressive disorders and a relatively greater expression of negative and cognitive symptoms. Negative and cognitive dimensions were the most stable elements of all the models. The concept of the depressive factor appeared to be too restrictive to describe a whole variety of the affective dimension.

A confirmatory factor analytic evaluation of the pentagonal PANSS model

The positive and negative syndrome scale (PANSS) is widely used in psychiatric research. Reflecting this common use, considerable attention has been applied to the psychometric properties of this instrument. However, despite the publication of numerous studies and analyses, it remains uncertain how best data from the PANSS should be analysed to best model the symptoms of schizophrenia. A resolution to these concerns seemed to be offered following the publication in 1997 of a large multisite factor analysis that produced the 'pentagonal model', which has subsequently been included in the 2000 revision of the PANSS user manual. However, to date, an independent confirmatory analysis of this model has not yet been published. The aim of this study was to test this model in a new independent sample with confirmatory factor analysis (CFA). Independent confirmation of the fit of the model is required to ensure that its implementation is informed by confirmation of its psychometric properties. CFA was performed in a sample of 347 subjects with schizophrenia. The analysis found that the model had inadequate goodness of fit. The use of the pentagonal model has similar difficulties as earlier models and more research is required to ascertain the optimal method for measuring symptom dimensions in research and clinical settings.

Correlation between clinical syndromes and neuropsychological tasks in unmedicated patients with recent onset schizophrenia

The aim of this study is to circumscribe the cognitive deficits according to schizophrenic syndromes in a population of sub-acute untreated patients. We have studied the cross-sectional correlation between cognitive deficits and schizophrenic symptoms, in a group of 24 untreated patients (including 17 neuroleptic-naive patients) with recent onset of the disease. A task of alertness, a working memory (WM) test (including two levels of difficulty) and an abbreviated version of the Wisconsin Card Sorting Test (WCST) were selected. WM deficits and poor performance on the WCST were highly correlated with disorganized symptoms, modestly with the positive syndrome and not with the negative syndrome. Thus, disorganized symptoms, more than any other, appear to be related to the impairment of executive function and WM in recent onset unmedicated patients with schizophrenia.

Cognitive performance in schizophrenia: relationship to regional brain volumes and psychiatric symptoms

In an all-male sample of schizophrenic patients stabilized by medication (n=62) and normal controls (n=27), we obtained neuropsychological test data and high-resolution whole brain magnetic resonance scans, as well as detailed psychiatric rating scales on a subset of the patients (n=47). Schizophrenic patients had significantly worse overall age-adjusted cognitive performance than normal controls (average z-score=-0.90, range=-0.60 to -1.81), which included relatively more severe deficits with different types of memory, psychomotor speed, verbal fluency and verbal abstraction. Schizophrenic patients also had significantly smaller bilateral volumes in gray but not white matter in the prefrontal region, superior temporal gyrus and whole temporal lobe, but no group differences were observed in the hippocampus and parahippocampus. Correlations between the brain regions and cognitive performance revealed different sets of significant relationships for the two groups, particularly in the prefrontal and hippocampal regions. In addition, inverse correlations were observed between certain cognitive abilities (psychomotor speed, cognitive flexibility and verbal fluency) and patients' psychiatric ratings, especially with measures of negative symptoms. The convergence of findings for schizophrenic patients regarding the prefrontal region, negative symptoms, psychomotor speed and cognitive flexibility suggests that schizophrenic negative symptoms may involve disruption of frontal-subcortical connections.

PANSS factors and scores in schizophrenic and bipolar disorders during an index acute episode: a further analysis of the cognitive component

To investigate the factor structure of psychotic symptoms, we compared the clinical characteristics of manic patients with those of schizophrenic patients evaluated with positive and negative syndrome scale (PANSS). The clinical symptoms of 148 bipolar patients and 86 schizophrenic patients hospitalized for an index psychotic episode were assessed. Schizophrenic patients showed more positive and cognitive symptoms than bipolars. The factor analysis of the two PANSS scores showed a three-factor solution with 'positive', 'negative' and 'mixed' depressive-activated factors for bipolars and 'positive', 'negative' and 'depressive' factors for schizophrenics. In both groups, the 'cognitive cluster' loaded on the first 'positive' factor while the 'lack of insight' (LOI) has a different meaning in the two groups, more related to the positive symptoms in the bipolar patients and more related to the negative symptoms in the schizophrenic patients. This finding suggests that LOI could be a non-unitary phenomenon in psychoses and it should be further explored to better elucidate differences in symptom structures between schizophrenic and bipolar disorders.

Symptom factors in early-onset psychotic disorders

OBJECTIVE

To examine the factor structure of symptom ratings in early-onset psychotic illnesses.

METHOD

Subjects were drawn from a 2-year prospective study of early onset psychotic disorders. Principal components analysis with orthogonal (varimax) rotation was used to create factors from baseline ratings on the Schedule for Positive Symptoms, the Schedule for Negative Symptoms, and the Brief Psychiatric Rating Scale for Children.

RESULTS

Youths with schizophrenia (n = 27), bipolar disorder (n = 22), and psychosis not otherwise specified (n = 20) were included. Four symptom factors were identified: negative symptoms, positive symptoms, behavioral problems, and dysphoria. Negative symptoms were predictive of the diagnosis of schizophrenia and treatment with antipsychotic medications. Neither behavior problems nor dysphoria were predictive of diagnosis. In subjects who completed follow-up assessments at year 1 (n = 49) and year 2 (n = 39), negative symptoms and behavioral problems predicted poorer functioning.

CONCLUSIONS

The four factors are clinically relevant, with both treatment planning and prognostic implications. Negative symptoms best differentiated schizophrenia from the other disorders. Behavior problems and dysphoria were nonspecific problems that occurred in all three disorders, which likely leads to misdiagnosis in community settings.

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.

Familiality of symptom dimensions in schizophrenia

The division of schizophrenic symptoms into three core dimensions - psychomotor poverty, reality distortion, and disorganisation - is well established. When factor analytic studies have included affective symptoms they have identified two additional dimensions - manic and depressive. Whether these five dimensions represent underlying psychopathology of a genetic or environmental aetiology remains unclear. The aims of this study were to perform factor analysis of symptoms in a group of familial schizophrenic patients and to investigate the familiality of the symptom dimensions identified, and their relationship to clinical characteristics. Symptoms were recorded, using the Operational Criteria Checklist for Psychotic Illness, for 155 Caucasian subjects with an RDC diagnosis of schizophrenia, schizoaffective disorder, or psychosis of unknown origin, from 61 families multiply affected with schizophrenia. Factor analysis indicated five symptom dimensions: depressive, manic, reality distortion, disorganisation, and psychomotor poverty. The psychomotor poverty, disorganisation, and manic dimensions were shown to be familial. Psychomotor poverty, disorganisation, and reality distortion were all associated with deterioration from premorbid functioning and chronic course of the disorder. In addition, psychomotor poverty was significantly related to poor premorbid functioning, as well as to single marital status and unemployment at onset. Disorganisation was significantly related to single marital status and unemployment at onset. The familiality of the psychomotor poverty, disorganisation, and manic dimensions supports their use in the delineation of homogeneous subsets for genetic studies.

Symptom dimensions in the course of childhood-onset schizophrenia

The symptom dimensions of childhood-onset schizophrenia (COS) are described by focussing on the clinical features of 44 patients at onset of illness during the first episode and at follow-up investigation 42 years after onset. All subjects were re-diagnosed according to DSM IV. The symptomatology was evaluated with the Positive and Negative Symptom Scale (PANSS) at onset and at follow-up. Two principal component factor analyses with varimax-rotation were applied to the complete items set of the PANSS. The frequencies of positive, negative, and global symptoms were compared longitudinally in an ANOVA-repeated measures design. The factor analysis revealed 5 orthogonal symptom dimensions (factors) at onset of psychosis: Cognition, social withdrawal, antisocial behaviour, excitement, and reality distortion. At follow-up a five-factor solution was found, too, but different dimensions emerged: a positive, negative, excitement, cognitive, and anxiety/depression component which fits to the 5-factor model of White et al. (1997). The first psychotic episode of EOS is accompanied with more unspecific symptoms such as social withdrawal and antisocial behavior. In the later stages of (COS) the structure of symptom dimensions changes to that known from adult-onset schizophrenia (AOS). The results indicate that COS and AOS are comparable nosological entities and that more than 3 dimensions are required to describe the relevant clinical symptom structure. Positive and global symptoms decreased significantly during the course of illness. The frequencies of negative symptoms did not change which demonstrates their disabling impact.

The three-syndrome model of schizophrenia: meta-analysis of an artefact

In two recent studies, Smith et al. (Smith, D.A., Mar, C.M., Turoff, B.K., 1998. The structure of schizophrenic symptoms: a meta-analytic confirmatory factor analysis. Schizophr. Res. 31, 57-70) and Grube et al. (Grube, B.S., Bilder, R.M., Goldman, R.S., 1998. Meta-analysis of symptom factors in schizophrenia. Schizophr. Res. 31, 113-120) used meta-analysis to examine the syndromal structure of schizophrenia. A limitation of both these studies is that the nine subscale scores from Andreasen's Scales for Assessment of Positive and Negative symptoms formed the basis of the analyses. These nine ratings, only four of which represent positive symptoms, do not adequately respresent the diversity of positive symptoms. A review of studies that examined the correlation between the individual items of these scales failed to support the classification of symptoms into these nine subgroups. Studies that indicated low numbers of syndromes suffered from one or more of the following limitations: (1) samples that were restricted to chronic schizophrenia, (2) exclusion of many items from analysis, and (3) a poor fit of the symptom model to the data. Studies not limited in these ways indicated the presence of at least 11 major dimensions of schizophrenic symptomatology, not including affective symptoms. It is concluded that the three-syndrome model of schizophrenia is largely an artefact of inadequate measurement at the symptom level.

Treatment of negative and cognitive symptoms

Persistent negative symptoms and cognitive dysfunction are a major cause of chronic disability in schizophrenia. Atypical antipsychotics such as clozapine, risperidone, and olanzapine induce significantly greater improvement in negative symptoms than that which is obtained with conventional agents. However, it remains unclear whether these agents treat core negative symptoms of schizophrenia, or simply induce less secondary psychopathology. A second approach for treatment of persistent negative symptoms is the use of N-methyl-d-aspartate (NMDA) receptor-stimulating agents, such as glycine, d-serine or d-cycloserine. These agents, when added to conventional or atypical antipsychotics, may induce significant additional reduction in both negative and cognitive symptoms.

Four behavioural syndromes of schizophrenia: a replication in a second inner-London epidemiological sample

In a previous large epidemiological survey of patients with strictly defined schizophrenia in the London borough of Camden, we extracted four behavioural syndromes (Social withdrawal, Thought disturbance, Anti-social behaviour and Depressed behaviour) by factor analysis of MRC Social Behaviour Schedule (SBS) data. These syndromes had significant differential relationships to symptoms assessed using the Manchester Scale (MS), symptom-derived syndromes, and social functioning variables. A second inner-London epidemiological survey of schizophrenia in South Westminster using identical methodology found the same four behavioural syndromes with identical core component items. The same four behavioural syndromes were extracted, whether applying strict Feighner diagnostic criteria (n=112) or broader DSM-III-R criteria (n=198). The four syndromes extracted from the Feighner positive sample showed relationships to symptoms and social functioning variables similar to those found in the original Camden study. However, the symptom-derived factors were not the same and did not conform to the three recognised symptom-based syndromes of schizophrenia. This successful replication suggests that assessment of the four behavioural syndromes of schizophrenia offers a different perspective on disability and a potentially relevant measure in clinical practice, clinical trials and studies of the neuropsychology and pathophysiology of schizophrenia.