ABSTRACT
According to the DSM IV-TR criteria (APA, 2000), the essential features of schizophrenia include the presence of both positive and negative symptoms for at least 6 months’ duration (see Table 5.1). Positive symptoms reflect a distortion or excess of perceptions while negative symptoms reflect restrictions in the range and intensity of emotional expression, thought, and language and in the production of goal-directed behavior. Positive symptoms include hallucinations, delusions, disorganized thought and language, and grossly disorganized behavior. Hallucinations are distorted sensory perceptions that may involve any of the senses, although auditory hallucinations are by far the most common. Delusions include distorted, exaggerated thinking and erroneous beliefs. The most common are persecutory delusions. Disorganized thinking in schizophrenia is characterized by incoherence, tangentiality, or frequent changes in thought and expression of ideas. Grossly disorganized behavior may be manifested in lack of goal-directed behavior or unpredictable agitation. Negative symptoms include the absence of normal emotional expression-flat affect, lack of behavior, and social withdrawal. It is important to note that there is considerable heterogeneity of symptoms across individuals; symptoms may vary, however, by age and gender. Psychotic symptoms have also been found to be influenced by cultural factors such as ethnicity and religion (David, 1999). Positive and negative symptoms are not unique to schizophrenia and are sometimes present in disorders such as Parkinson’s and Alzheimer diseases and temporal lobe epilepsy (Getz et al., 2002).
