Positive and negative symptoms in the psychoses: Principal components analysis of items from the scale for the assessment of positive symptoms and the scale for the assessment of negative symptoms

doi:10.1016/0010-440X(94)90059-Q

Comprehensive Psychiatry

Volume 35, Issue 2, March–April 1994, Pages 135-144

https://doi.org/10.1016/0010-440X(94)90059-Q Get rights and content

Abstract

The present study investigated the factor structure of the items contained in Andreasen's scales for the assessment of positive and negative symptoms (SAPS and SANS) by use of a series of principal components analyses (PCAs) with oblique rotations of the axes. It was found that the structure could be summarized by three major components labeled negative symptoms, thought disorder, and delusions/hallucinations. Dimensionality could meaningfully be increased to five components. Negative symptoms was found to separate into two components that we labeled negative signs and social dysfunctions. The delusions/hallucinations factor could be separated into two components, delusions and hallucinations, with “loss of boundary” delusions being related to both factors. Delusions of persecution were independent of other symptoms. The thought disorder factor did not decompose meaningfully within the investigated dimensionality. A two-factor solution did not explain the correlation between symptoms adequately. The results do not support the simple dichotomy between positive and negative symptoms in psychosis, but suggest that a wider dimensional concept may be more useful in future studies.

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The SAPS and SANS together are comprised of 49 individual symptom items, e.g. ‘auditory hallucinations’, in addition to nine sub-scale global symptom severity summary scores, e.g. ‘global rating of hallucinations’. Whilst individual symptom level analyses of SAPS and SANS ratings typically generate around ten factors (Minas et al., 1994; Peralta and Cuesta, 1999; Toomey et al., 1997; Vazquez-Barquero et al., 1996), global rating level analyses generate far fewer (typically three to four), including positive, negative and disorganisation syndromes (Dollfus and Petit, 1995; John et al., 2003; Klimidis et al., 1993; Liddle, 1987; Peralta and Cuesta, 1999; Toomey et al., 1997). Consequently, existing studies and reviews of the literature that include data from the SAPS and SANS (Grube et al., 1998; Smith et al., 1998) may underestimate the number of psychotic symptom dimensions as a result of the predominance of global level analyses (Stuart et al., 1999).
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There has been some interest in detecting the factor structure of psychotic symptoms generally (Emsley et al., 2003; Peralta et al., 2013), and one of the advantages of this analytic approach (i.e., factor analysis) is that it allows for the reduction of heterogeneity in data from a measurement instrument by identifying a group of coherent dimensions. Across different types of available tools measuring delusions, the Scale for the Assessment of Positive Symptoms (SAPS; Andreasen, 1984) has been extensively utilized, and several studies have performed factor analyses in order to identify the latent dimensions amongst its items (e.g., John et al., 2003; Minas et al., 1994; Peralta and Cuesta, 1999; Toomey et al., 1997). Those studies conducted an item-level factor analysis of SAPS items, and they included both delusions and non-delusion items.
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Citation Excerpt :
In a first-episode psychosis population, Malla et al. (2002) also investigated the factor structure of negative symptoms, revealing a two-factor structure for negative symptoms: (1) affective flattening/alogia (except poverty of content of speech) and (2) avolition/anhedonia. In the studies that included both the SAPS and SANS, the attention factor, including poverty of content of speech, and inappropriate affect, routinely loaded with other disorganization symptoms of schizophrenia (Malla et al., 2002; Minas et al., 1994; Peralta and Cuesta, 1999). Given the important distinction between primary and secondary negative symptoms, and the question of whether the presence of secondary negative symptoms influence the factor structure of negative symptoms, Kelley et al. (1999) examined individuals with schizophrenia or schizoaffective disorder both on and off antipsychotic medication.
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Positive and negative symptoms in the psychoses: Principal components analysis of items from the scale for the assessment of positive symptoms and the scale for the assessment of negative symptoms

Abstract

Psychiatr Res

Compr Psychiatry

Negative v positive schizophrenia: definition and validation

Arch Gen Psychiatry

Negative symptoms in schizophrenia: definition and reliability

Arch Gen Psychiatry

Evaluation of positive and negative symptoms in schizophrenia

Psychiatr Biol

Ventricular enlargement in schizophrenia: relationship to positive and negative symptoms

Am J Psychiatry

Phenomenology of psychosis

Curr Opin Psychiatry

Royal Park Multidiagnostic Instrument for the Psychoses. II. Development, reliability, and validity

Schizophr Bull

Royal Park Multidiagnostic Instrument for the Psychoses. I. Rationale and review

Schizophr Bull

Predictive validity of a linear regression equation

Br J Math Stat Psychol