Clustering Of Symptoms

The characteristic symptoms of schizophrenia that have been described above may be classified in many different ways. Prominent among the attempts that have been proposed up to now are Bleuler's classifications in fundamental and accessory symptoms and in primary versus secondary symptoms, as well as Schneider's division in first- and second-rank symptoms. In recent years, the attention of researchers and clinicians alike has focused on the distinction between positive and negative symptoms.

Bleuler identified two sets of symptoms, one descriptive, the other aetiopathogenetic. The two dichotomies are distinct, although they are defined by partially overlapping features. The first set distinguishes between fundamental and accessory symptoms. Fundamental symptoms are present at all times and in all cases. They include disturbances in association and affect, ambivalence and autism (the four A's). All other symptoms encountered in schizophrenia are accessory symptoms, including hallucinations, delusions, catatonia and behavioural problems. Accessory symptoms may be absent at times and even throughout the whole course and they may appear in other types of illness.

The specificity and inter-rater reliability of Bleuler's fundamental symptoms have been questioned in a number of studies [44].

The second set distinguishes between primary and secondary symptoms. Primary symptoms are direct manifestations of the disorder, while secondary symptoms are viewed as psychological reactions of the personality to the disease process. Primary symptoms consist above all in disturbances of associations, while the bulk of the other symptoms described in schizophrenia are secondary symptoms.

For the diagnosis of schizophrenia, Kurt Schneider ascribed a particular importance to 11 abnormal experiences for which he coined the term ''first-rank symptoms''. Schneider considered that first-rank symptoms were pathognomonic of schizophrenia, provided that they could not be linked in one way or another to an organic cause. other abnormal experiences that could contribute to the diagnosis were termed ''second-rank symptoms''. A diagnosis of schizophrenia could also be made when only symptoms of second rank were present. The presence or absence of first- or second-rank symptoms did not carry any theoretical or prognostic significance.

The 11 first-rank symptoms included: thoughts experienced as spoken-aloud or echoed; thought withdrawal, thought insertion and thought broadcasting; voices heard commenting on the patient's thoughts or actions and voices discussing the person in the third person; feelings, impulses and volitional acts experienced as under the control of some external force or agency; somatic passivity and delusional perception. The presence of just one first-rank symptom was considered sufficient for the diagnosis, provided that its presence could be firmly established.

The prevalence of first-rank symptoms has been investigated in a number of studies. The frequency of any first-rank symptom in patients with schizophrenia varied from one study to another, ranging from 28% to 72% [45- 47]. According to the results of the International Pilot Study of Schizophrenia [20], the prevalence of first-rank symptoms varied from one participant centre to another, from a low 31% in Moscow to a high 79% in Taipei.

The specificity of first-rank symptoms has been investigated by Abrams and Taylor [48], Carpenter et al [49], Taylor and Abrams [50], and Koehler et al [51]. According to the results of these studies, first-rank symptoms are not pathognomonic of schizophrenia, but may occur during a depressive or manic episode in a substantial number of patients.

Interest in the positive-negative distinction [52] led to the development of a variety of instruments designed to assess positive and/or negative symptoms. Prominent among these instruments are the Scale for the Assessment of Negative Symptoms (SANS) [53,54] and the Scale for the Assessment of Positive Symptoms (SAPS) [55]. The SANS includes items that describe different aspects of affective flattening, avolition-apathy, anhedonia-asociality and attentional impairment. The SAPS includes items that describe hallucinations, delusions, bizarre behaviour and formal thought disorder. The first factor analysis on the two scales showed that the correlations between the negative symptoms were quite high, as was the internal consistency of the SANS. The correlations between the positive symptoms were weaker, as was the internal consistency of the SAPS. Subsequent analyses of 15 studies of the SANS and the SAPS led to the conclusion that the symptoms fall into three natural dimensions [43]. While negative symptoms remain more or less the same, positive symptoms subdivide into a first dimension that reflects psychoticism (hallucinations and delusions) and a second dimension that includes disorganized/bizarre behaviour, positive formal thought disorder and disorganized speech, and inappropriate affect.

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