Positive and negative symptoms of schizophrenia: past, present, and future

Nonverbal social perception and symptomatology in schizophrenia

This study examined the relationship between nonverbal social perception and symptomatology in schizophrenia. Schizophrenic patients (n=28) and normal controls (n=28) were given the profile of nonverbal sensitivity test (PONS). Patients' symptoms were rated with the brief psychiatric rating scale (BPRS). Schizophrenic subjects performed significantly more poorly than normal subjects in their ability to decode nonverbal cues. In addition, normal subjects improved their accuracy significantly more than patients when provided with additional cues per scene to decode. The patients' total PONS score was not significantly correlated with the BPRS summary scores for positive or negative symptoms, but was significantly correlated with the individual positive symptom of conceptual disorganization. Subjects classified as having paranoid schizophrenia (n=11) on the basis of chart diagnoses performed significantly better on the PONS than did undifferentiated schizophrenic subjects (n=13). The discussion reviews how these results contribute to our understanding of social deficits in schizophrenia.

Relationship between symptom dimensions and neurocognitive functioning in schizophrenia: a meta-analysis of WCST and CPT studies. Wisconsin Card Sorting Test. Continuous Performance Test

Cognitive deficits have been hypothesized to be differentially related to the negative, positive and disorganization dimensions of schizophrenia symptoms. In this article, we quantitatively review the published literature on the relationships between symptom dimensions in schizophrenia and performance on the two most widely applied tests of executive functioning and sustained attention, the Wisconsin Card Sorting Test (WCST) and the Continuous Performance Test (CPT). Meta-analyses were conducted on studies that reported correlational data for the relations between performance on these tests and scales of positive and negative symptoms. The more recent distinction between disorganization and reality distortion was also taken into account. The results showed statistically significant relationships of negative symptoms with worse performance on the WCST and the CPT. Disorganization symptoms showed a significant positive correlation with perseverations on the WCST, but not with CPT performance. In contrast, reality distortion symptoms and general scores for all positive symptoms did not correlate with either measure. Although some correlations were statistically significant, the observed associations between psychiatric symptoms and cognitive performance were typically weak, suggesting relative independence of these disease processes.

Defining the phenotype of schizophrenia: cognitive dysmetria and its neural mechanisms

All research on schizophrenia depends on selecting the correct phenotype to define the sample to be studied. Definition of the phenotype is complicated by the fact that there are no objective markers for the disorder. Further, the symptoms are diverse, leading some to propose that the disorder is heterogeneous and not a single disorder or syndrome. This article explores an alternative possibility. It proposes that schizophrenia may be a single disorder linked by a common pathophysiology (a neurodevelopmental mechanism), which leads to a misconnection syndrome of neural circuitry. Evidence for disruption in a specific circuit is explored: the cortical-thalamic-cerebellar-cortical circuit (CCTCC). It is suggested that a disruption in this circuit leads to an impairment in synchrony, or the smooth coordination of mental processes. When synchrony is impaired, the patient suffers from a cognitive dysmetria, and the impairment in this basic cognitive process defines the phenotype of schizophrenia and produces its diversity of symptoms.

Symptom classification of schizophrenia changes with the duration of illness

Our starting hypothesis was that schizophrenic symptomatology changes over time. This hypothesis explains conflicting reports on schizophrenic symptom structures as a consequence of different durations of illness in the samples studied to date. Therefore a sample of 258 schizophrenic in-patients (with ICD-10 diagnoses F20) was categorized according to illness duration. A factor analysis was performed on the 8 items of the Manchester Scale for three subgroups (duration < 10 years, 10> or =20 years and > or = 20 years). For those patients whose illness duration was less than 10 years, 'formal thought disorder' was not related to any other mental state, whereas for those whose duration was 10 years or longer, it was correlated with 'negative symptoms'. In the < 10 years group, 'anxiety and depression syndrome' and 'positive symptoms' formed one complex, but these symptoms were separated into two distinct syndromes in the > or = 20 years group. Thus we were able to demonstrate that the classification of symptoms changes with increasing duration of illness.

Negative, positive, and disorganized symptom dimensions in schizophrenia, major depression, and bipolar disorder

We compared the factor structure of positive and negative symptoms in schizophrenia (N = 214), major depression (N = 97), and bipolar disorder (N = 58) to determine whether schizophrenia factors would generalize to mood disorders. A study of schizophrenia and mood disorders identified patients whose symptoms were evaluated with the Scale for the Assessment of Negative Symptoms and the Scale for the Assessment of Positive Symptoms. We conducted principal component analyses with orthogonal rotation on the global ratings. The factor structure replicated earlier findings of three factors (negative, positive, and disorganization) in groups with schizophrenia, combined mood disorders, and psychotic symptoms, regardless of diagnosis. An additional negative symptom factor was found in the major depression group. The bipolar group did not have a disorganization factor. Similar symptom factors in schizophrenia and mood disorders suggest a continuity in the major affective and psychotic disorders that appears to reflect the underlying dimension of a psychotic process.

Use of a quantitative trait to map a locus associated with severity of positive symptoms in familial schizophrenia to chromosome 6p

A number of recent linkage studies have suggested the presence of a schizophrenia susceptibility locus on chromosome 6p. We evaluated 28 genetic markers, spanning chromosome 6, for linkage to schizophrenia in 10 moderately large Canadian families of Celtic ancestry. Parametric analyses of these families under autosomal dominant and recessive models, using broad and narrow definitions of schizophrenia, produced no significant evidence for linkage. A sib-pair analysis using categorical disease definitions also failed to produce significant evidence for linkage. We then conducted a separate sibpair analysis using scores on positive-symptom (psychotic), negative-symptom (deficit), and general psychopathology-symptom scales as quantitative traits. With the positive symptom-scale scores, the marker D6S1960 produced P = 1.2 x 10(-5) under two-point and P = 5.4 x 10(-6) under multipoint analyses. Using simulation studies, we determined that these nominal P values correspond to empirical P values of .034 and .0085, respectively. These results suggest that a schizophrenia susceptibility locus on chromosome 6p may be related to the severity of psychotic symptoms. Assessment of behavioral quantitative traits may provide increased power over categorical phenotype assignment for detection of linkage in complex psychiatric disorders.

Validity of specific subscales of the positive and negative symptom scales in older schizophrenia outpatients

We investigated the construct validity of subscales of the Scale for the Assessment of Positive Symptoms (SAPS) and the Scale for the Assessment of Negative Symptoms (SANS) along with other measures of psychopathology in 109 schizophrenia outpatients aged 45-84 years. Scores on subscales of the SAPS, SANS and Brief Psychiatric Rating Scale (BPRS) and on the Hamilton Depression Scale (HAM-D) were subjected to a principal components analysis and orthogonal rotation followed by an extension analysis. In both analyses, three of four SAPS subscales had their highest loading on the positive symptom factor and four of five SANS subscales had their highest factor loading on the negative symptom factor. The SAPS bizarre behavior subscale, however, had a much higher loading on the depressive symptom factor than on the positive symptom factor, and the SANS avolition-apathy subscale had moderate loadings on both the negative symptom factor and the depressive symptom factor. The use of SAPS and SANS subscales to represent two constructs was largely (but not entirely) validated among middle-aged and elderly schizophrenia outpatients. The SAPS bizarre behavior subscale and, to a lesser extent, the SANS avolition-apathy subscale appear to represent in this older population a separate construct which may be related to depressive symptoms.

Early identification and treatment of schizophrenia: conceptual and ethical considerations

To identify and start treatment of schizophrenic patients at an early stage has been a matter of growing interest in recent years (Alanen 1994; Birchwood 1992; Docherty et al. 1978; Falloon 1992; Lieberman et al. 1993). However, we are not aware of any controlled study definitively concluding that early treatment of schizophrenia is favorable. Many researchers discuss the topic, for example, regarding outcome and prognosis (Falloon 1992) or treatment response (Alanen 1994; Lieberman et al. 1993). In this article we take a closer look at the idea of early treatment of schizophrenia by analyzing the concept of early schizophrenia/early psychosis at an epistemological level and discuss related ethical problems.