Tests and diagnosisBy 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 and exams. These tests and exams generally include:
- Laboratory tests. These may include a complete blood count (CBC), other blood tests that may help to rule out other conditions with similar symptoms, screening for alcohol and drugs, and 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 spelled out in the Diagnostic and Statistical Manual of Mental Disorders (DSM). This manual is published by the American Psychiatric Association and 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 common symptoms of the disorder — delusions, hallucinations, disorganized speech, disorganized or catatonic behavior, or presence of negative symptoms for a significant amount of time during one month
- Experience significant impairment in the ability to work, attend school or perform normal daily tasks
- Have had symptoms for at least six months
There are several subtypes of schizophrenia, but not everyone easily fits into a specific category. The five most common subtypes are:
- Paranoid. Characterized by delusions and hallucinations, this type generally involves less functional impairment and offers the best hope for improvement.
- Catatonic. People with this subtype don't interact with others, get into bizarre positions, or engage in meaningless gestures or activities.
- Disorganized. Characterized by disorganized thoughts and inappropriate expressions of emotion, this type generally involves the most functional impairment and offers the least hope for improvement.
- Undifferentiated. This is the largest group of people with schizophrenia, whose dominant symptoms come from more than one subtype.
- Residual. This type is characterized by extended periods without prominent positive symptoms, but other symptoms continue.
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