Tests and diagnosis

By Mayo Clinic Staff

When doctors suspect someone has schizophrenia, they typically ask for medical and psychiatric histories, conduct a physical exam, and run medical and psychological tests, including:

  • Tests and screenings. These may include a lab test called a complete blood count (CBC), other blood tests that may help rule out conditions with similar symptoms, and screening for alcohol and drugs. The doctor may also request imaging studies, such as an MRI or CT scan.
  • Psychological evaluation. A doctor or mental health provider will check mental status by observing appearance and demeanor and asking about thoughts, moods, delusions, hallucinations, substance abuse, and potential for violence or suicide.

Diagnostic criteria for schizophrenia

To be diagnosed with schizophrenia, a person must meet the criteria in the Diagnostic and Statistical Manual of Mental Disorders (DSM). This manual, published by the American Psychiatric Association, is used by mental health providers to diagnose mental conditions.

Diagnosis of schizophrenia involves ruling out other mental health disorders and determining that symptoms aren't due to substance abuse, medication or a medical condition. In addition, a person must have at least two of the following symptoms most of the time during a one-month period, with some level of disturbance being present over six months:

  • Delusions
  • Hallucinations
  • Disorganized speech (indicating disorganized thinking)
  • Extremely disorganized behavior
  • Catatonic behavior, which can ranges from a coma-like daze to bizarre, hyperactive behavior
  • Negative symptoms, which relate to reduced ability or lack of ability to function normally

At least one of the symptoms must be delusions, hallucinations or disorganized speech.

The person shows a significant decrease in the ability to work, attend school or perform normal daily tasks most of the time.

The American Psychiatric Association eliminated the previous subtypes of schizophrenia — paranoid, disorganized, catatonic, undifferentiated and residual — because of poor reliability. These subtypes weren't shown to be valid and didn't help in determining which treatment might be best for a specific subtype.

Jan. 24, 2014