Positive and negative symptoms in the psychoses: multidimensional scaling of SAPS and SANS items

Schizophrenia Research, 10 (1993) 211-218 0 1993 Elsevier Science Publishers B.V. All rights reserved

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271 0920-9964/93/$06.00

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Positive and negative Symptoms in the psychoses: multidimensional scaling of SAPS and SANS items Dear Editor, I was intrigued by the recent publication of Minas and colleagues (1992) which confirms thought disorder (conceptual disorganization) as a separate, independent construct of positive symptoms distinct from hallucinations and delusions. This work adds to a growing body of literature which indicates the symptom construct of positive symptoms, includes at least two clusters, a distinction which may have biologic relevance. At the 145th Annual Meeting of the American Psychiatric Association in 1991, I presented a confirmation analysis on a San Diego cohort of chronic schizophrenic patients. We used three predefined symptom constructs of SAPS and SANS items to predict DSM-IIIR subtypes. Table 1 shows a classification analysis used to determine the predictive validity for these symptom constructs. It may be noted that diagnostic subtypes were correctly predicted in over 60% of all patients. Fig. 1 is a graphical representation of the canonical factors used in the prediction of schizophrenic subtypes. Negative symptoms and conceptual disorganization (thought disorder) helped differentiate between subtypes while hallucinations/ delusions did not emerge as an independent factor. These results like those of Minas et al. provide strong evidence for conceptual disorganization/

TABLE

1

CIassification analysis Clinical diagnosis

Disorganized Undifferentiated Paranoid

Predicted diagnosis Disorganized

Undifferentiated

Paranoid

20 6 2

3 21 2

1 6 13

% Correct: disorganized, noid 16.5%.

83.3%; undifferentiated,

63.6%; para-

“1

-3~,...,.,.,,.,..,,...,....,... -3

-2

,

-1

0

1

2

3

Disorganized Factar

Fig. 1. Two diagnoses.

symptom

factors

that

predict

clinical

subtype

thought disorder as an independent construct of psychotic symptoms. Our results were confirmatory, providing validity to a predetermined definition of conceptual disorganization which included inappropriate affect, poverty of content of speech, bizarre behavior, and the positive formal thought disorder items (derailment, tangentiality, incoherence, illogicality, circumstantiality, pressure of speech, distractible speech, and clanging). Minas and colleagues in their exploratory multidimensional analysis defined a thought disorder construct which included all the same SANS and SAPS items except inappropriate affect and bizarre behavior. In their analysis, inappropriate affect was highly correlated with both thought disorder and negative symptoms and bizarre behavior correlated poorly with all three primary symptom constructs. Overall, our results and those of Minas reach similar conclusions through very different statistical methods. Both studies suggest the use of

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statistical models of modeling the interrelationships between symptom clusters to explain the heterogeneity of psychotic disorders and predict clinically relevant diagnostic subgroups. Recent studies have tended to focus only on negative symptoms. Though negative symptoms contribute a significant proportion of the treatment refractoriness and poor prognosis in psychotic disorders, thought disorder/conceptual disorganization is also a poor prognostic indicator which is often poorly responsive to available treatment modalities. Future studies of the psychotic disorders should address both negative symptoms and conceptual disorganization. Potential interactions between these and other core symptom constructs need to be explored. Computerized models which take into account the heterogeneity in symptom presentation may help define more homogeneous

subgroups for investigation in the neurochemical and genetic basis of psychotic disorders. Sincerely, John T. Moranville, M.D. Assistant Clinical Professor of Psychiatry University of California, San Francisco San Francisco VA Medical Center (V116-M) 4150 Clement Street San Francisco, CA 9412 1, USA

REFERENCE

Minas, I.H., Stuart, G.W., Klimidis, %I., Jackson, H.J., Singh, B.S. and Copolov, D.L. (1992) positive and negative symptoms in the psychoses: Multidimensional scaling of SAPS and SANS items. Schizophr. Res. 8, 143-156.