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.

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:

• Depression. Delusions that focus on a physical abnormality or disease that isn't real, known as somatic delusions, sometimes occur in people with depression.
• Bipolar Disorder. Paranoia and delusions of grandeur (the belief that one has a special power or mission) can occur in people with bipolar disorder during the manic phase. Sometimes it is difficult even for doctors to differentiate between these two disorders. Evidence suggests that they may share certain genetic factors that make some families vulnerable to either one.
• Schizophrenia-Like Psychoses. Several other conditions exhibit schizophrenia-like psychoses but do not meet the diagnostic criteria for schizophrenia. Such conditions may be variations of entirely different diseases and are classified as schizoaffective disorder, schizophreniform psychosis, and atypical and brief reactive schizophrenia.
• Alcohol and Drug Abuse. Either substance abuse itself or withdrawal from drugs or alcohol can trigger psychosis. Because of the high risk for substance abuse among people with schizophrenia, it is important that the health professional distinguish psychosis triggered by drugs or alcohol from a schizophrenic episode. Usually, the diagnosis is confirmed if the psychosis ends after withdrawal from drugs or alcohol, and returns if the patient returns to alcohol or substance abuse.
• Medical Illnesses. Other causes of psychotic symptoms include cancer in the central nervous system, encephalitis, neurosyphilis, thyroid disorders, Alzheimer's disease, epilepsy, Huntington's disease, multiple sclerosis, stroke, Wilson's disease, some vitamin B deficiencies, and systemic lupus erythematosus.
• 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.

Imaging Techniques

Many brain imaging techniques can detect changes in the brain structure that relate to specific sets of symptoms in schizophrenia. These imaging techniques include magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT), and positron emission tomography (PET). Such techniques are used as research tools. However, research continues in evaluating whether they may be useful for identifying candidates for early treatment among high-risk young people with early warnings signs of schizophrenia and brain damage.