Diagnosis of Schizophrenia

Unfortunately, there is no laboratory test for schizophrenia. The complex spectrum of schizophrenia symptoms cannot be gauged with methods like the mental status examination. Diagnosis is made by clinically examining the following:

  • Person's family history
  • Emotional history
  • Current symptoms
  • Presence of other disorders (differential diagnosis)

It may be difficult to diagnose acute (quick, severe, and brief) schizophrenia during its first episode. Often, physicians must wait to establish recurrence, chronicity, and intensity, especially with regard to negative symptoms. For these reasons, a physician's main goal in early diagnosis is to distinguish a person's disturbance from other conditions, including other psychotic disorders, organic disorders, and drug-related conditions.

Differential diagnosis for schizophrenia involves distinguishing the disorder from other mental health conditions such as bipolar disorder, schizoaffective disorder, and brief psychotic disorder. Schizophrenia-related changes in mood can include mania and depression. However, these changes in mood typically do not meet the criteria for full-blown mania or depression, which occur in bipolar disorder.

Diagnosing schizophrenia is further complicated by the fact that changes in mood occur in its early, active, and late phases. Schizoaffective disorder features depression or mania along with schizophrenic symptoms. The following three diagnostic criteria are used to diagnose this disorder:

  • Change in mood corresponds to active phase symptoms
  • Changes in mood must be present for a significant time during psychotic episode
  • Delusions and hallucinations must be present for 2 weeks without changes in mood

The prognosis for schizoaffective disorder is typically better than that for schizophrenia, but worse than that for mood disorder.

Brief psychotic disorder features one or many schizophrenic symptoms, including delusions, hallucinations, disorganized speech and behavior, and flattened affect. There is usually a clear trigger, and symptoms last less than 1 month. So the duration criterion for diagnosis of schizophrenia is not met.

Organic medical conditions may also produce schizophrenia-like symptoms. Certain frontal brain disorders, encephalitis (swelling of the brain due to viral infection), and delirium must be ruled out. Delirium is a serious type of confusion that may involve hallucination, incoherent speech, and disorientation. It is caused by a number of things, including illness, shock, drug abuse, and anxiety and may closely resemble schizophrenia.

Drugs of abuse, including amphetamines and PCP, or phencyclidine ("angel dust"), may cause delusions, hallucinations, wild behavior, and babbling. Phencyclidine can even cause what appear as schizophrenic negative symptoms, like emotionless stupor. A physician will determine whether the drug is causing and sustaining symptoms that resemble schizophrenia, or aggravating the preexisting symptoms of the disease. This usually requires that he or she observe the person during drug abstinence.

Finally, other psychiatric disorders, like obsessive-compulsive disorder (OCD), posttraumatic stress disorder (PTSD), and schizoid personality may resemble schizophrenia.

Obsessive thoughts, hallucinations, disorganized behavior, paranoia, and delusional thinking are common in one or more of these diseases and may appear as symptoms of schizophrenia. The severity and duration of these symptoms, in addition to the person's age and psychological history, differentiate these disorders from schizophrenia. Also, schizophrenia is often diagnosed as one of several subtypes.

In addition to investigating a person's family history of mental illness, a physician will use the American Psychiatric Association's criteria for diagnosis to assess their emotional past and current symptoms.

The American Psychiatric Association (APA) specifies the criteria for diagnosis of schizophrenia in the DSM-IV, the Diagnostic and Statistical Manual of Mental Disorders. Included here are the definitive symptoms, duration, and severity.

Diagnostic Criteria for Schizophrenia

A. Characteristic symptoms: Two (or more) of the following, each present for a significant portion of time during a 1-month period (or less if successfully treated):

  • Delusions
  • Hallucinations
  • Disorganized speech (e.g., frequent derailment, incoherence)
  • Grossly disorganized or catatonic behavior
  • Negative symptoms (e.g., affective flattening, alogia, avolition)

Note: Only one Criterion A symptom is required if delusions are bizarre or hallucinations consist of a voice keeping up a running commentary on the person's behavior or thoughts, or two or more voices conversing with each other.

B. Social/occupational dysfunction: For a significant portion of the time since the onset of the disturbance, one or more major areas of functioning such as work, interpersonal relations, or self-care are markedly below the level achieved prior to the onset (or when the onset is in childhood or adolescence, failure to achieve expected level of interpersonal, academic, or occupational achievement).

C. Duration: Continuous signs of the disturbance persist for at least 6 months. This 6-month period must include at least 1 month of symptoms (or less if successfully treated) that meet Criterion A (i.e., active-phase symptoms) and may include periods of prodromal or residual symptoms. During these prodromal or residual periods, the signs of the disturbance may be manifested by only negative symptoms or two or more symptoms listed in Criterion A present in an attenuated form (e.g., odd beliefs, unusual perceptual experiences).

D. Schizoaffective and Mood Disorder exclusion: Schizoaffective Disorder and Mood Disorder With Psychotic Features have been ruled out because either (1) no Major Depressive, Manic, or Mixed Episodes have occurred concurrently with the active-phase symptoms; or (2) if mood episodes have occurred during active-phase symptoms, their total duration has been brief, relative to the duration of the active and residual periods.

E. Substance /general medical condition exclusion: The disturbance is not due to the direct physiological effects of a substance (e.g., a drug of abuse, a medication) or a general medical condition.

F. Relationship to a Pervasive Developmental Disorder (PDD): If there is a history of Autistic Disorder or another Pervasive Developmental Disorder, the additional diagnosis of Schizophrenia is made only if prominent delusions or hallucinations are also present for at least a month (or less if successfully treated).

APA. Diagnostic and Statistical Manual of Mental Disorders, 4th ed. 1994. Washington, DC: American Psychiatric Association (APA).

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 01 Feb 2001

Last Modified: 24 Sep 2010