Diagnosis

Diagnosis

The doctor will use one or more verbal screening tests to help determine whether a patient's symptoms meet the criteria for schizophrenia. Because no single symptom is specific to schizophrenia, a diagnosis may be made when one or more of the following conditions is present:

• 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 emotional unresponsiveness with a flat speaking tone).
• If the patient has particularly bizarre delusions or hallucinations, even in the absence of other characteristic symptoms.
• 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. The patient's social and personal relationships would also have deteriorated since the onset of symptoms.

Possible Markers of Schizophrenia

Experts are investigating tests of specific phenomenon that might suggest a higher risk for the presence of schizophrenia.

• Eye Tracking Dysfunction. A dysfunction in eye tracking is a genetic trait that is strongly associated with schizophrenia and may reflect abnormalities in the frontal regions of the brain. (Some experts believe that this is such a powerful marker in patients with close relatives with schizophrenia that it can be used as a predictor. This trait can be detected only by a health professional using special equipment.)
• Impaired Prepulse Inhibition. Prepulse inhibition (PPI) is a phenomenon in which a low sound (weak stimulus) that occurs before a loud sound (a strong stimulus) reduces a patient's startle response to the loud sound. PPI is impaired in schizophrenia.

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).

Among the conditions that may resemble schizophrenia are the following: