Three syndromes in schizophrenia: validity in young patients with recent onset of illness

DSM-IV "criterion A" schizophrenia symptoms across ethnically different populations: evidence for differing psychotic symptom content or structural organization?

There is significant variation in the expression of schizophrenia across ethnically different populations, and the optimal structural and diagnostic representation of schizophrenia are contested. We contrasted both lifetime frequencies of DSM-IV criterion A (the core symptom criterion of the internationally recognized DSM classification system) symptoms and types/content of delusions and hallucinations in transethnic schizophrenia populations from Australia (n = 776), India (n = 504) and Sarawak, Malaysia (n = 259), to elucidate clinical heterogeneity. Differences in both criterion A symptom composition and symptom content were apparent. Indian individuals with schizophrenia reported negative symptoms more frequently than other sites, whereas individuals from Sarawak reported disorganized symptoms more frequently. Delusions of control and thought broadcast, insertion, or withdrawal were less frequent in Sarawak than Australia. Curiously, a subgroup of 20 Indian individuals with schizophrenia reported no lifetime delusions or hallucinations. These findings potentially challenge the long-held view in psychiatry that schizophrenia is fundamentally similar across cultural groups, with differences in only the content of psychotic symptoms, but equivalence in structural form.

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.

Distribution of symptom dimensions across Kraepelinian divisions

BACKGROUND

Dimensional structures are established for many psychiatric diagnoses, but dimensions have not been compared between diagnostic groups.

AIMS

To examine the structure of dimensions in psychosis, to analyse their correlations with disease characteristics and to assess the relative contribution of dimensions v. diagnosis in explaining these characteristics.

METHOD

Factor analysis of the OPCRIT items of 191 Maudsley Family Study patients with schizophrenia, mood disorders with psychosis, schizoaffective disorder, and other psychotic illnesses, followed by regression of disease characteristics from factor scores and diagnosis.

RESULTS

Five factors were identified (mania, reality distortion, depression, disorganisation, negative); all were more variable in schizophrenia than in affective psychosis. Mania was the best discriminator between schizophrenia and affective psychosis; the negative factor was strongly correlated with poor premorbid functioning, insidious onset and worse course. Dimensions explained more of the disease characteristics than did diagnosis, but the explanatory power of the latter was also high.

CONCLUSIONS

Kraepelinian diagnostic categories suffice for understanding illness characteristics, but the use of dimensions adds substantial information.

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.

Perceptual Organization in Schizophrenia Spectrum Disorders: Empirical Research and Theoretical Implications

The research into perceptual organization in schizophrenia spectrum disorders has found evidence for and against a perceptual organization deficit and has interpreted the data from within several different theoretical frameworks. A synthesis of this evidence, however, reveals that this body of work has produced reliable evidence for deficits in schizophrenia, as well as for the clinical, stimulus, and task parameters associated with normal and abnormal performance. Recent models of cognition have also advanced understanding of the underlying pathophysiological processes of perceptual organization dysfunction in schizophrenia spectrum disorders. These suggest that deficits in perceptual organization may be one manifestation of a wider disturbance in the integration of contextually related information across space and time.

Exploration of dimensions of psychopathology in neuroleptic-naïve patients with recent-onset schizophrenia/schizophreniform disorder

Previous studies have suggested that schizophrenic psychopathology segregates into three orthogonal dimensions, viz., psychosis, negative and disorganization. Most of these reports were based on studies on medicated patients with varying degrees of chronicity. The present study aimed at exploring the dimensionality of psychopathology rated on the Scale for the Assessment of Negative Symptoms (SANS) and the Scale for the Assessment of Positive Symptoms (SAPS) in a sample of 43 neuroleptic-naïve patients with recent-onset schizophrenia/schizophreniform disorder. Principal Components Analysis (PCA) of SANS and SAPS global ratings, excluding inattention but including inappropriate affect as a separate global rating, revealed that the symptoms segregated into three dimensions, viz., negative (affective flattening, alogia, avolition anhedonia and inappropriate affect), psychosis (delusions and hallucinations) and disorganization (positive formal thought disorder and bizarre behavior). Cumulatively these three dimensions explained 74.07% of the variance. The results suggest that the three dimensions of schizophrenic psychopathology are valid even in neuroleptic-naïve, recent-onset patients with schizophrenia/schizophreniform disorder. PCA of the SANS and SAPS individual items revealed similar findings, but psychotic symptoms loaded under two components, thus yielding a four-factor solution; however, this observation needs to be confirmed in a larger sample of neuroleptic-naïve schizophrenic patients.

The evolution of symptoms in the early course of non-affective psychosis

Most previous studies investigating the factor structure of psychosis have focussed on chronic samples. First episode samples with longitudinal follow up are few. To investigate the stability and validity of symptom factors, a sample of 257 patients with DSM IV nonaffective psychoses were assessed using the PANSS during the acute first episode and at 3- and 18-month follow up. Exploratory factor analysis of the changes in PANSS item scores over time gave a five-factor solution. This was consistent with the solutions to factor analyses at the initial assessment and each of the follow-ups. However, there was progression over follow-up. Confirmatory factor analysis demonstrated that symptom ratings at 18-month follow-up fitted the models from existing research, in relatively chronic samples, better than the ratings at the initial assessment. A psychomotor poverty factor showed most stability over time and a positive symptom factor most change. Factors showed different associations with demographic and external variables, further supporting their validity.

Perseveration in schizophrenia: failure to generate a plan and relationship with the psychomotor poverty subsyndrome

Although perseveration in the Wisconsin Card Sorting Test (WCST) has been studied extensively in schizophrenia, the underlying cognitive dysfunctions are not yet clear. In schizophrenia, perseveration has been found to relate to frontal and striatal abnormalities. Therefore, both a failure to generate a plan as seen in patients with frontal abnormalities, or a failure to execute a plan as observed in Parkinson patients, who suffer primarily from striatal abnormalities, could explain perseveration in schizophrenia. The aim of the present study was to distinguish between these two cognitive dysfunctions, which are described by Frith in his routes-to-action model. The main difference between these dysfunctions is the ability to use external guidance. In the present study, 39 schizophrenic patients and 36 healthy controls were assessed with the California Verbal Learning Test (CVLT) and the WCST, in which use of external guidance can be measured, and with the Positive and Negative Syndrome Scale (PANSS) to determine the relationship with symptomatology. The results showed that half of the schizophrenic patients showed perseveration, which could be explained by a failure to generate a plan and was related to the psychomotor poverty subsyndrome. No evidence was found for a failure to execute a plan. Type of antipsychotic medication used (atypical vs. typical) proved not relevant. The results are discussed in the light of evidence for involvement of the dorsolateral prefrontal cortex in perseveration in schizophrenia.

Culture and schizophrenia and other psychotic disorders

The comparative study of schizophrenia and related disorders across cultures has come a long way since Kraepelin advocated its cause, following his trip to Java at the beginning of the last century. The principal development since then has been the burgeoning of interest in the field, culminating in innovative and ambitious international collaborative research by the WHO. Despite reservations about covert ideology or about the more overt methodologic difficulties, the balance of evidence from these and similar studies suggests that: It is feasible to conduct such research despite the numerous hazards. There is a certain uniformity to the way schizophrenia presents globally; there are equally significant cultural differences. The outcome of schizophrenia appears to be better in developing, than developed cultures; reasons for this are far from clear, nevertheless, it can be safely assumed that culturally-determined processes, whether social or environmental, are partly responsible. Overall, the study of schizophrenia in different cultures has proved useful in establishing the pancultural and the culture-specific properties of this and related disorders.

Neuropsychological correlates of schizophrenic syndromes in patients treated with atypical neuroleptics

There is widespread evidence that schizophrenic symptomatology is best represented by three syndromes (positive, negative, disorganized). Both the disorganized and negative syndrome have been found to correlate with several neurocognitive dysfunctions. However, previous studies investigated samples predominantly treated with typical neuroleptics, which frequently induce parkinsonian symptoms that are hard to disentangle from primary negative symptoms and may have inflated correlations with neurocognition. A newly developed psychopathological instrument called the Positive and Negative and Disorganized Symptoms Scale (PANADSS) was evaluated in 60 schizophrenic patients. Forty-seven participants treated with atypical neuroleptics performed several neurocognitive tasks.A three-factor solution of schizophrenic symptomatology emerged. Negative symptomatology was associated with diminished creative verbal fluency and digit span backward, whereas disorganization was significantly correlated with impaired Stroop, WCST and Trail-Making Test B performance.Data suggest that disorganization is associated with tasks that demand executive functioning. Previous findings reporting correlations between negative symptomatology and neurocognition may have been confounded by the adverse consequences of typical neuroleptics.

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.

Set-maintenance and set-shifting problems in schizophrenic subtypes: relationship to dysfunctions of the fronto-striatal loops

Research with patients suffering from Parkinson's disease and frontal lobe lesions has shown that disturbances in the fronto-striatal loops in the brain can cause perseveration. Perseveration is a core symptom of schizophrenia, yet the cause is not known. For schizophrenic patients disorders of many parts of the fronto-striatal loops are found, for example disturbances of the prefrontal cortex and the striatum. Perseveration in schizophrenia can be explained with set-maintenance problems, related to dysfunction of the prefrontal cortex, or with set-shifting problems that are related to disorders in the striatum. These set-maintenance and set-shifting problems can be distinguished with neuropsychological tests. Regarding the bloodflow patterns for the different subtypes of schizophrenia three problems are expected as explanations for perseveration: set-maintenance problems concerning abstract information, set-maintenance problems shifting between stimuli and enhanced set-shifting with cues.

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.