behavior. Schizophrenics whose symptoms are primarily positive are classified as Type I.
Negative symptoms of schizophrenia are associated with premorbid inferior social functioning and poor prognoses. They include flat affect, poverty of speech, anhedonia, apathy, and avolition. Individuals whose symptoms are predominately negative are classified as Type II schizophrenics (McGlashan & Fenton, 1992).
Theoretical Explanations of Schizophrenia
There are several etiological theories of schizophrenia, one set of which are biological; in general, these theories postulate that the disorder arises from imbalances in brain chemistry and/or structures (Sue, Sue & Sue, 1994). One promising biological theory is the "Dopamine Hypothesis" (Siever, Davis & Gorman, 1991).
The Dopamine Hypothesis holds that schizophrenia may be caused by excess dopamine at certain synaptic sites; this excess is said to be due to either faulty dopamine releasing presynaptic neurons or to some sort of oversensitivity of dopamine receptors. Support
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