Schizophrenia Diagnosis

The diagnosis of schizophrenia can be challenging for a number of reasons. In addition to the lack of a single symptom that is diagnostic of the illness, there are also no laboratory tests, biochemical changes, imaging studies, or psychological tests that can definitively establish a diagnosis. While many people suspected of having schizophrenia display clear positive symptoms of psychosis, others may have negative symptoms that are far less evident. Schizophrenia is therefore considered to be a diagnosis of exclusion; a definitive diagnosis may not be made until other possible explanations for the symptoms have been ruled out. In the broadest sense, this involves three steps.

First, the clinician must rule out organic causes (e.g., medical diseases, drugs, or toxic substances).

Second, having established no organic explanation for the symptoms, the clinician must determine whether the psychotic symptoms result from schizophrenia or another mental disorder, such as affective disorder (e.g., depression or bipolar disorder). In patients with affective disorders, the psychotic symptoms if they occur at all generally coincide with the mood disturbance. In addition, the psychotic symptoms of schizophrenia tend to be more bizarre and less understandable than those seen in affective disorders.

Third, once a patient is diagnosed with schizophrenia, the clinician may classify the illness into a subtype depending on the predominant symptoms and their pattern or duration of occurrence. A number of guidelines and approaches to diagnosing schizophrenia have been developed, including the DSM-IV-TR.

Regardless of which guidelines are used, all require the clinician to make detailed observations of the person's symptoms and behaviors. These are often made during the psychiatric interview with the aid of the Mental Status Examination (MSE). In addition, clinicians may create a target list of symptoms that can be used to monitor changes in the patient.