The existence of two subtypes of schizophrenia (positive and negative) is well established. The evidence in favor of other subtypes, particularly a disorganized subtype, is still the subject of some debate. The aim of the study reported in this article is to investigate the possibility of further subtypes of schizophrenia by applying a particular method of cluster analysis to a particular set of data. Ward's method of cluster analysis was applied to the Positive and Negative syndrome Scale (PANSS) scores of 138 patients, defined as having schizophrenia by one of four diagnostic criteria. The validity of the cluster solution was assessed both by examining differences between clusters on a number of clinical characteristics recorded for each patient and by comparing the results obtained from the PANSS with those derived from a cluster analysis using two other instruments (the Scale for the Assessment of Negative Symptoms and the Scale for the Assessment of Positive Symptoms). Results from the cluster analysis suggest the existence of at least four subtypes of schizophrenia: positive, negative, mixed, and disorganized. A fifth subtype includes patients with few symptoms, suggesting the simple schizophrenia named by Bleuler. Evidence for the validity of these subtypes was provided by the differences observed between the clusters on a number of clinical characteristics and by the similarity of the cluster solution obtained from the different instruments. In conclusion, the negative-positive dichotomy in schizophrenia is an oversimplification, and the existence of a more complex structure needs to be taken into account in future research.

Numerous data support the hypothesis that dopamine (DA) plays a crucial role in reward-related processes and in incentive learning in animals and man. The possibility that various neuroleptics exhibiting a high affinity for the dopaminergic D2 (and D3) receptors could reinforce DA transmission was studied using the conditioned place preference paradigm (CPP) in rats. This was done by examining the ability of these compounds to potentiate the reinforcing properties of food in hungry rats subjected to a version of the CPP paradigm which consisted of repeated pairings of food with a single environmental cue, the floor texture of an open field. During the test session when food was no longer available in the open field, the increase in the time spent by drug-free rats on the food-paired texture was assumed to indicate the perceived rewarding value of the food. This time was significantly lengthened when the specific D2 (D3)-receptor antagonists sulpiride (4 mg/kg), amisulpride (0.5, 1 mg/kg) or pimozide (0.03, 0.06 mg/kg) were administered before the food conditioning sessions. Larger doses of these compounds as well as haloperidol, metoclopramide and the non-specific D1-D2 antagonist, chlorpromazine, regardless of the doses tested, did not exhibit this effect, but rather reduced the food-induced CPP, an action usually associated with neuroleptics. The positive effects of amisulpride was reversed by a D1 receptor antagonist, SCH 23390 (0.01 mg/kg). These results suggest that, as with amphetamine (0.5 mg/kg), some D2-specific neuroleptics enhance the incentive value of food in a narrow range of low doses, an effect proposed to reflect a "prohedonic" property.(ABSTRACT TRUNCATED AT 250 WORDS)

We assessed the subjective quality of life (QOL) of 30 deficit schizophrenic patients compared to 112 nondeficit schizophrenic patients. The deficit patients did not differ in term of QOL, total score of positive symptoms, general psychopathology from the nondeficit patients. This result suggested an absence of impact of primary negative symptoms on the subjective QOL in schizophrenic patients.

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