How is schizophrenia diagnosed?
If symptoms are present, your doctor will perform a complete medical history and physical examination. Although there are no laboratory tests to specifically diagnose schizophrenia, the doctor might use various diagnostic tests — such as MRI or CT scans or blood tests — to rule out physical illness as the cause of your symptoms.
If the doctor finds no physical reason for the symptoms, he or she might refer the person to a psychiatrist or psychologist, healthcare professionals who are specially trained to diagnose and treat mental illnesses. Psychiatrists and psychologists use specially designed interview and assessment tools to evaluate a person for schizophrenia. The doctor or therapist bases his or her diagnosis on the person’s report of symptoms, and his or her observation of the person’s attitude and behavior.
The doctor or therapist then determines if the person’s symptoms point to a specific disorder as outlined in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), which is published by the American Psychiatric Association and is the standard reference book for recognized mental illnesses. According to the DSM-5, a diagnosis of schizophrenia is made if a person has two or more core symptoms, one of which must be hallucinations, delusions, or disorganized speech for at least one month. The other core symptoms are gross disorganization and diminished emotional expression. Other DSM-5 criteria for a diagnosis of schizophrenia include:
- Level of work, interpersoanl relations or self-care is significantly below what it was before the start of symptoms.
- Signs of disturbance that have lasted at least 6 months.
- Schizoaffective disorder and depressive or bipolar disorder with psychotic symptoms have been ruled out.
- The disturbance is not caused by substance abuse or another medical condition.