Diagnosis

• 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. In fact, sometimes it is difficult even for experts 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.