According to the American Psychiatric Association (DSM-IV, 1994), a diagnosis of schizophrenia may be given if patients meet the following criteria:
A. At least two of the following symptoms lasting for at least one month in the active phase (exception: only one symptom if it involves bizarre delusions or if hallucinations involve a running commentary on the person or two or more voices talking with each other):
3. Disorganized speech (incoherent or frequent derailment)
4. Grossly disorganized or catatonic behavior
5. Negative symptoms (flat affect, avolition, alogia, or anhedonia)
B. During the course of the disturbance, functioning in one or more areas such as work, social relations, and self-care has deteriorated markedly from premorbid levels (in the case of a child or adolescent, failure to reach expected level of social or academic development)
C. Signs of the disorder must be present for at least six months
D. Schizoaffective and mood disorders with psychotic features must be ruled out
E. The disturbance is not substance-inducted or caused by organic factors.
According to Sue, Sue and Sue (1994), differentiating between schizophrenia and other psychotic disorders is somewhat difficult because many other psychoses share at least some of the symptoms; however the authors report that of the most common symptoms, the most discriminant and therefore most helpful ones in diagnosing the condition and distinguishing it from other psychoses are auditory hallucinations, voices speaking to the patient, thought alienation, thoughts spoken aloud, and delusions of control.
As to the symptoms of the disorder, McGlashan and Fenton (1992) state that these are broadly classified as either positive or negative. Positive symptoms are those present during the active phase of the disorder but which disappear with treatment; they include delusions, hallucinations, thought disorder, and bizarre...