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, schizo-affective 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. Schizo-affective 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 schizo-affective 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.

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

Published: 01 Feb 2001

Last Modified: 08 May 2014