Schizophrenia symptom clusters

The second revolution began in the past 10 years with the arrival of the atypical antipsychotics. Although the atypicals are no panacea for schizophrenia, they represent an advance in at least three areas. First, they lessen the burden of antipsychotic side effects and therefore frequently increase adherence dramatically. Second, the atypicals may treat all of the schizophrenia symptom clusters (positive, negative, mood, cognitive), whereas the typical antipsychotics chiefly treat the positive symptoms. Third, atypical antipsychotics sometimes benefit patients whose schizophrenia is unresponsive to typical antipsychotics. 

Schizophrenia is characterized by three partially independent symptom clusters 875... 

Schizophrenia is characterized by three partially independent symptom clusters. These symptom clusters are designated positive symptoms, negative symptoms and cognitive impairments [1], The positive symptoms are the most dramatic and are manifestations of psychosis. 

Schizophrenia is a debilitating disorder affecting 1 % of the global population. It is a pervasive disease, affecting many aspects of mental function. Positive, negative, affective, and cognitive symptom clusters characterize schizophrenia (Table 1). 

Cluster A Personality Disorders (Schizotypal PD, Schizoid PD, Paranoid PD). These are the odd and eccentric personality disorders. They all share certain features in common with schizophrenia, but schizotypal PD in particular appears to be most closely related to schizophrenia. The schizophrenia-like symptoms of these personality disorders (e.g., magical thinking, paranoia, social withdrawal) are less severe and generally don t impair social or employment function as severely as schizophrenia. 

The symptoms during this phase of illness are not particularly specific to schizophrenia. They often resemble, in many respects, depression or even one of the Cluster A personality disorders. The decision to initiate antipsychotic medication at this stage depends on the degree of certainty of the diagnosis, the severity of the symptoms, and the risk and benefits of the medication. 

Research into the risk factors for Cluster A personality disorders has focused on genetic factors. In particular, many researchers have looked for a shared genetic linkage between these disorders and schizophrenia. Only schizotypal personality appears to be genetically linked to schizophrenia. It may be that STPD exists on a biological continuum with schizophrenia. In other words, STPD could theoretically be a far milder variant of Axis I schizophrenia. There is less evidence linking PPD or SPD to schizophrenia nevertheless, certain characteristic symptoms of these other disorders also overlap with schizophrenia. 

Other research has studied how childhood experiences may contribute to the development of a Cluster A personality disorder. Psychosocial explanations revolve around the observation that there is a degree to which distrust is a rational response to certain experiences. Some have theorized that cold and indifferent parenting can contribute to the disinterest in relationships that characterizes Cluster A disorders. It is in fact likely that a genetic predisposition to subclinical personality traits that mirror the positive and/or negative symptoms of schizophrenia may combine with certain developmental experiences that conspire to the development of a Cluster A personality disorder. 

Schizotypai Personaiity Disorder (STPD). Patients with STPD most closely resemble those with schizophrenia. They have parallels to both the positive and negative symptoms of schizophrenia. Of the three Cluster A personality disorders, most medication research has been conducted in STPD though it is also quite limited. 

Waddington, J. L., 8c Youssef, H. A. (1986b). An unusual cluster of tardive dyskinesia in schizophrenia Association with cognitive dysfunction and negative symptoms. American Journal of Psychiatry, 143, 1162-1165. 

Animal models of schizophrenia are intended to examine specific neurochemical or anatomical theories of the illness, and not to model the cluster of symptoms that characterizes the illness, since these are largely subjective. Models are divided into two types, pharmacological models and lesions models (Marcotte et al., 2001). 

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