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positive and negative symptoms schizophrenia

Positive and Negative Symptoms of schizophrenia

Strauss, Carpenter, & Bartko introduced the distinction between positive and negative symptoms, promoting awareness of an important aspect of heterogeneity in schizophrenia. Carpenter emphasized the challenge of this distinction to the conceptualization of schizophrenia. Positive symptoms are the presence of abnormal functioning, such as hallucinations and delusions, whereas negative symptoms reflect an inadequacy of normal functioning, such as affective flattening, poverty of speech, and social withdrawal. Crow proposed a Type I dimension of schizophrenia characterized by prominent positive symptoms, responsiveness to antipsychotics, an acute onset, an episodic course, and good premorbid adjustment.

Because of the role of DA in positive symptoms, Crow suggested that the Type I dimension is due to a neurochemical imbalance that involves dopamine. In contrast, Crow’s Type II dimension involves prominent negative symptoms, a chronic course, an insidious onset, poor premorbid adjustment, intellectual deterioration, and a poor response to antipsychotics. Early studies of the activity-withdrawal dimension in schizophrenia (based on ratings of ward behavior among hospitalized schizophrenics) are relevant to understanding negative symptoms. Active schizophrenics are characterized as restless, loud, overtalkative, overactive, and as having many friends and interests; withdrawn patients showed an absence of these features. Withdrawal has been related to chronicity, poor premorbid adjustment, negative symptoms, anhedonia, and high levels of (purportedly cortical) arousal as measured by skin potential and two perceptual measures. The activity-withdrawal dimension is important in this context because the balance between the BAS and BIS should influence the degree of activity versus withdrawal. This perspective suggests that negative-symptom, withdrawn patients show a dominance of passive avoidance due to high BIS activity and, quite likely, a deficiency in BAS activity. The low BAS activity could be due to a temperament-based weak BAS or to depression from a variety of sources (genetic factors, life events, demoralization, institutionalism, etc.). Assuming that negative-symptom patients are BIS-dominant, the high arousal is presumably aversive arousal and mediates the stress response in the diathesis-stress model. If so, one would expect that anxiolytic drugs would be of some benefit in treating a subset of schizophrenic patients.

In a review of pharmacological treatment, Wolkowitz and Pickar found that 30–50% of schizophrenic patients show favorable response to benzodiazepines and that this response is predicted by a range of symptoms including negative symptoms, core psychotic symptoms, and negative affect symptoms. These findings are consistent with the notion that BIS activation may contribute to a wide range of symptoms. At the other end of the activity-withdrawal dimension, the active behavior, interest in rewarding activities, and dominance of positive rather than negative symptoms among active schizophrenics all point to a contribution to liability from activation of the BAS. These patients have features of mania, further indicating BAS activation. Similarly, the good premorbid adjustment (extraverted behavior) and the contribution of dopamine to positive symptoms in Crow’s Type I dimension suggest a BAS contribution to liability.

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