Evidence for the validity of negative symptoms

Positive and Negative Symptoms Are Associated with Distinct Effects on Predictive Saccades

The predictive saccade task is a motor learning paradigm requiring saccades to track a visual target moving in a predictable pattern. Previous research has explored extensively anti-saccade deficits observed across psychosis, but less is known about predictive saccade-related mechanisms. The dataset analysed came from the studies of Crawford et al, published in 1995, where neuroleptically medicated schizophrenia and bipolar affective disorder patients were compared with non-medicated patients and control participants using a predictive saccade paradigm. The participant groups consisted of medicated schizophrenia patients (n = 40), non-medicated schizophrenia patients (n = 18), medicated bipolar disorder patients (n = 14), non-medicated bipolar disorder patients (n = 18), and controls (n = 31). The current analyses explore relationships between predictive saccades and symptomatology, and the potential interaction of medication. Analyses revealed that the schizophrenia and bipolar disorder diagnostic categories are indistinguishable in patterns of predictive control across several saccadic parameters, supporting a dimensional hypothesis. Once collapsed into predominantly high-/low- negative/positive symptoms, regardless of diagnosis, differences were revealed, with significant hypometria and lower gain in those with more negative symptoms. This illustrates how the presentation of the deficits is homogeneous across diagnosis, but heterogeneous when surveyed by symptomatology; attesting that a diagnostic label is less informative than symptomatology when exploring predictive saccades.

Phospholipase C-β1 Hypofunction in the Pathogenesis of Schizophrenia

Schizophrenia is a mental disorder that is characterized by various abnormal symptoms. Previous studies indicate decreased expression of phospholipase C-β1 (PLC-β1) in the brains of patients with schizophrenia. PLC-β1-null (PLC-β1(-/-)) mice exhibit multiple endophenotypes of schizophrenia. Furthermore, a study of PLC-β1 knockdown in the medial prefrontal cortex of mice has shown a specific behavioral deficit, impaired working memory. These results support the notion that disruption of PLC-β1-linked signaling in the brain is strongly involved in the pathogenesis of schizophrenia. In this review, we broadly investigate recent studies regarding schizophrenia-related behaviors as well as their various clinical and biological correlates in PLC-β1(-/-) and knockdown mouse models. This will provide a better understanding of the pathological relevance of the altered expression of PLC-β1 in the brains of patients with schizophrenia. Evidence accumulated will shed light on future in-depth studies, possibly in human subjects.

Duration of untreated psychosis and social function: 1-year follow-up study of first-episode schizophrenia

BACKGROUND

In first-episode schizophrenia, longer duration of untreated psychosis (DUP) predicts poorer outcomes.

AIMS

To address whether the relationship between DUP and outcome is a direct causal one or the result of association between symptoms and/or cognitive functioning and social functioning at the same time point.

METHOD

Symptoms, social function and cognitive function were assessed in 98 patients with first-episode schizphrenia at presentation and 1 year later.

RESULTS

There was no significant clinical difference between participants with short and long DUP at presentation. Linear regression analyses revealed that longer DUP significantly predicted more severe positive and negative symptoms and poorer social function at 1 year, independent of scores at presentation. Path analyses revealed independent direct relationships between DUP and social function, core negative symptoms and positive symptoms. There was no significant association between DUP and cognition.

CONCLUSIONS

Longer DUP predicts poor social function independently of symptoms. The findings underline the importance of taking account of the phenomenological overlap between measures of negative symptoms and social function when investigating the effects of DUP.

The Camden Schizophrenia Surveys. III: Five-year outcome of a sample of individuals from a prevalence survey and the importance of social relationships

BACKGROUND

Most studies of outcome in schizophrenia have focused on incidence cohorts or samples identified through specialist mental health services; population-based samples provide a more complete picture of the effectiveness of community services.

AIMS

To examine whether outcome predictors, derived from studies of selected patients with prolonged schizophrenia, would emerge in a largely community-dwelling population sample.

METHODS

A follow-up sample of 114 adults with schizophrenia was identified via two censuses of key informants conducted for two prevalence surveys in North London, five years apart. Symptomatic, clinical and functional outcomes were assessed after five years. A composite score was derived for each individual. Multiple Linear Regression analyses were conducted in two phases to derive a best subset of predictors for global outcome.

RESULTS

After five years, 33% were worse and 62% were better overall. The four best predictors (social isolation, living apart from relatives, longer illness and being an inpatient at first census) accounted for 32% of the variance in outcome of those with schizophrenia and related diagnoses.

CONCLUSIONS

Social relationships during the course of illness are an important predictor of overall outcome and relationships with friends and family each seem to make a positive contribution. Policy and service developments should focus on improving participation in community life for people with schizophrenia, particularly their social connectedness.

Phenotype of schizophrenia: a review and formulation

The discovery of the pathophysiology(ies) for schizophrenia is necessary to direct rational treatment directions for this brain disorder. Firm knowledge about this illness is limited to areas of phenomenology, clinical electrophysiology, and genetic risk; some aspects of dopamine pharmacology, cognitive symptoms, and risk genes are known. Basic questions remain about diagnostic heterogeneity, tissue neurochemistry, and in vivo brain function. It is an illness ripe for molecular characterization using a rational approach with a confirmatory strategy; drug discovery based on knowledge is the only way to advance fully effective treatments. This paper reviews the status of general knowledge in this area and proposes an approach to discovery, including identifying brain regions of dysfunction and subsequent localized, hypothesis-driven molecular screening.

Neuroplasticity and schizophrenia

This article's title is also the name of a workshop sponsored by the International Congress on Schizophrenia Research that was focused on an appraisal of the potential role of neuroplastic processes in the etiology or course of schizophrenia. The workshop brought together clinical investigators of schizophrenia and basic scientists who study various aspects of neuroplasticity, including central nervous system (CNS) development, learning and memory, and drug action. The goal was to identify special opportunities to advance knowledge and understanding of schizophrenia pathology, treatment, or prevention by applying neuroplasticity concepts as a framework to theories of the illness. Although the focus of this workshop was schizophrenia, the phenomena considered are pertinent to other disorders, such as depression and drug abuse.

Defining the schizophrenia phenotype

Schizophrenia is a complex disease with multifactorial etiology. The schizophrenia phenotype has been traditionally defined by chronic psychosis and functional deterioration. However, the boundary of the phenotype is likely to be more extensive than the one defined by chronic psychosis. This is highlighted by the findings of subtle, schizophrenia- like deficits in the nonschizophrenic, first-degree relatives of schizophrenic patients. Subtle clinical signs and symptoms, cognitive impairment particularly in attention and memory, and neurophysiologic deficits such as in sensory gating and smooth-pursuit eye movements all define aspects of the schizophrenia phenotype.

Relationships between social competence, psychopathology and work performance and their predictive value for vocational rehabilitation of schizophrenic outpatients

Earlier studies suggest that social competence has a higher predictive value for vocational outcome than psychopathology. These studies, however, show methodological shortcomings, including the fact that the instruments used for assessing social competence, psychopathology and work performance are strongly interrelated. The present study, involving a population of 34 chronically schizophrenic outpatients enrolled in a vocational rehabilitation program, was conducted in order to determine: (1) how closely the Role Play Test, the Positive and Negative Syndrome Scale and the Work Behavior Assessment Scale are related to each other; and (2) whether social competence is a better predictor of work performance and outcome of vocational rehabilitation than psychopathology. Factor analysis has revealed that the instruments are interrelated, mainly in the dimensions of negative symptoms, social relationships, non-verbal measures of social competence and conceptual disorganization. In backward regression analyses, psychopathological indicators proved to be the best predictors of work performance both cross-sectionally as well as in the longterm course. In the traditional two-syndrome model of schizophrenic psychopathology only negative symptoms were left in the regression model. In a four-dimension model the disorder of relating and the conceptual disorganization dimension were the best predictors. Differences between disorder of relating and social competence, assessed by the Role Play Test, are discussed here as well as the implications of this study for rehabilitation.

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

The heterogeneity of schizophrenia constitutes an impediment in the identification of reliable biological markers of the illness and aetiological factors. The two syndrome concept of the illness has proved a powerful stimulus in this endeavour. There is however evidence now to regard this construct as inadequate and in need of refinement. Using a sample of young patients with early onset of illness who fulfilled the Research Diagnostic Criteria for schizophrenia, we have shown that three rather than two dimensions better describe the pathology of the illness. The results of factor analysis showed these syndromes, termed disorganization, positive, and negative syndromes, to account for 65% of the total variance of the psychopathology of the disorder. The negative syndrome was associated with disturbed pre-morbid functioning while the disorganization syndrome bore significant association with early onset of illness, poorer socio-educational attainment, and impairment on neuropsychological tests, especially those designed to evaluate frontal lobe functioning. The positive syndrome was not associated with any of the assessed variables. These results provide strong support for the validity of the three-syndrome construct even among a sample of non-institutionalized patients.

An analysis of the clinical features of familial schizophrenia

Clinical features of familial schizophrenia were examined in 169 siblings from 80 families. Factor analysis of symptoms produced a negative symptom factor (affective flattening and negative thought disorder), a disorganization factor (inappropriate affect and positive thought disorder) and a reality distortion factor (delusions and hallucinations). The negative symptom factor correlated positively with duration of illness and poor outcome. The disorganization factor correlated positively with poor outcome and early age at onset. The only clear correlation between these factors and affective symptoms was a negative one between the negative symptom factor and mania. There were no significant gender differences in age at onset, factor scores or outcome. The implication of these findings in relation to recent research in the areas of psychopathology and epidemiology are discussed.

Positive and negative symptoms in families with schizophrenia

Positive and negative symptoms are measurable characteristics that may represent core features of schizophrenia and offer a quantitative approach for studying the genetics of schizophrenia and related disorders. The Positive and Negative Syndrome Scale (PANSS) was used to assess 72 members of five families segregating schizophrenia. The study confirmed high internal reliability of PANSS scales in this sample with diverse lifetime diagnoses. Gender but not alcoholism affected scores. Schizophrenia/schizoaffective and schizophrenia spectrum disorder groups had higher mean scores for the positive and negative scales than other lifetime diagnostic groups, consistent with genetic transmission of these symptoms. Positive and negative symptom patterns did not subtype families. The results support the validity of positive and negative symptom measures as independent dimensions in familial schizophrenia.

Are there more than two syndromes in schizophrenia? A critique of the positive-negative dichotomy

A sample of 115 DSM-III-R schizophrenics was studied by means of the SANS and SAPS. A factor analysis from the nine subscales and two symptoms (inappropriate affect and poverty of content) and a review of the previous factor analyses suggest that schizophrenic symptoms cannot be appropriately classified into positive and negative syndromes. The low internal consistency of the SAPS suggests that the positive symptoms are not a homogeneous syndrome. Our results fit better with Liddle's model of three syndromes (negative, delusion-hallucination and disorganisation syndromes). It is argued that we are far from a valid classification of schizophrenic symptoms and the positive-negative dichotomy appears to be an oversimplification.