Diagnosis

A doctor will make a diagnosis of schizophrenia based on a patient’s symptoms and how long they have lasted.

Diagnostic Criteria

Psychiatrists use as diagnostic criteria:

• If a patient has at least one active flare-up lasting a month or more. The flare-up consists of at least two characteristic symptoms (such as hallucinations, delusions, evidence of disorganized thinking and speaking, and emotional unresponsiveness with a flat speaking tone). If the patient has particularly bizarre delusions or hallucinations, these alone will qualify as a diagnostic sign of schizophrenia.
• If major areas of functioning (work, school, interpersonal relations, self-care) have been significantly affected since the disturbance began
• If certain symptoms are present for at least 6 months, even in the absence of active flare-ups. Such symptoms include marked social withdrawal, peculiar behavior (talking to oneself, severe superstitiousness), vague and incoherent speech, or other indications of disturbed thinking, as well as continued deterioration of the patient's social and personal relationships.

Ruling Out Other Conditions

The common hallmarks of schizophrenia are also symptoms that can occur in dozens of other psychologic and medical conditions, as well as with certain medications. Shared symptoms include delusions, hallucinations, disorganized and incoherent speech, a flat tone of voice, and bizarrely disorganized or catatonic behavior (such as lack of speech, muscular rigidity, and unresponsiveness).

Conditions that may resemble schizophrenia include:

• Other Psychiatric Disorders. Bipolar disorder, schizoaffective disorder, and depression can all have psychotic elements that resemble schizophrenia. Autism and pervasive developmental disorder can share some characteristics of schizophrenia but are an entirely separate diagnosis.
• Alcohol and Drug Abuse. Either substance abuse itself or withdrawal from drugs or alcohol can trigger psychosis.
• Medical Illnesses. Other causes of psychotic symptoms include cancer in the central nervous system, infections such as encephalitis and syphilis, thyroid disorders, Alzheimer's disease, epilepsy, Huntington's disease, multiple sclerosis, stroke, Wilson's disease, and some B vitamin deficiencies..
• Medication Reactions. Many medications may induce psychosis as a side effect, and some can precipitate delusions and severe confusion. Such medication-induced symptoms are most often observed in elderly patients.

Review Date: 01/27/2011
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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