John Nash, a U.S. mathematician and joint winner of the 1994 Nobel Prize for Economics, who had Schizophrenia. His life was the subject of the 2001 Academy Award-winning film A Beautiful Mind.

Schizophrenia is diagnosed based on criteria in either the American Psychiatric Association’s fifth edition of the Diagnostic or Statistical Manual of Mental Disorders (DSM 5), or the World Health Organization's International Statistical Classification of Diseases and Related Health Problems, the ICD-10. These criteria use the self-reported experiences of the person and reported abnormalities in behavior, followed by a clinical assessment by a mental health professional. Symptoms associated with Schizophrenia occur along a continuum in the population and must reach a certain severity before a diagnosis is made. As of 2013 there is no objective test.

 

Criteria In 2013, the American Psychiatric Association released the fifth edition of the DSM (DSM 5). The broad definition of Schizophrenia was not changed, but DSM 5: 1. eliminates the classic subtypes of Schizophrenia, 2. adds new psychopathological dimensions, 3. clarifies cross-sectional and longitudinal course specifiers, 4. eliminates special treatment of Schneider's first-rank symptoms, 5. more clearly defines the distinction between Schizophrenia and schizoaffective disorder, and 6. Clarifies the relationship between Schizophrenia and catatonia. In the older, fourth revised edition of the DSM (DSM-IV-TR), to be diagnosed with Schizophrenia, three diagnostic

 

criteria had to be met: 1. Characteristic symptoms: Two or more of the following, each present for much of the time during a one-month period (or less, if symptoms remitted with treatment) Delusions Hallucinations Disorganized speech, which is a manifestation of formal thought disorder Grossly disorganized behavior (e.g. dressing inappropriately, crying frequently) or catatonic behavior Negative symptoms: Blunted affect (lack or decline in emotional response), alogia (lack or decline in speech), or avolition (lack or decline in motivation)

If the delusions are judged to be bizarre, or hallucinations consist of hearing one voice participating in a running commentary of the person's actions or of hearing two or more voices conversing with each other, only that symptom is required above. The speech disorganization criterion is only met if it is severe enough to substantially impair communication. 2. Social or 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. 3. Significant duration: Continuous signs of the disturbance persist for at least six months. This six-month period must include at least one month of symptoms (or less, if symptoms remitted with treatment). The ICD-10 criteria are typically used in European countries, while the DSM-IV-TR criteria are used in the United States and to varying degrees around the world, and are prevailing in research studies. The ICD-10 criteria put more emphasis on Schneiderian first-rank symptoms. In practice, agreement between the two systems is high.

If signs of disturbance are present for more than a month but less than six months, the diagnosis of schizophreniform disorder is applied. Psychotic symptoms lasting less than a month may be diagnosed as brief psychotic disorder, and various conditions may be classed as psychotic disorder not otherwise specified. Schizophrenia cannot be diagnosed if symptoms of mood disorder are substantially present (although schizoaffective disorder could be diagnosed), or if symptoms of pervasive developmental disorder are present unless prominent delusions or hallucinations are also present, or if the symptoms are the direct physiological result of a general medical condition or a substance, such as abuse of a drug or medication.

Diagnosis of Subtypes
 

The DSM-IV-TR contains five sub-classifications of Schizophrenia, although the developers of DSM 5 are recommending they be dropped from the new Paranoid type: Delusions or auditory hallucinations are present, but thought disorder, disorganized behavior, or affective flattening is not. Delusions are persecutory and/or grandiose, but in addition to these, other themes such as jealousy, religiosity, or somatization may also be present. (DSM code 295.3/ICD code F20.0) Disorganized type: Named hebephrenic Schizophrenia in the ICD. Where thought disorder and flat affect are present together. (DSM code 295.1/ICD code F20.1)

Catatonic type: The subject may be almost immobile or exhibit agitated purposeless movement. Symptoms can include catatonic stupor and waxy flexibility. (DSM code 295.2/ICD code F20.2) Undifferentiated type: Psychotic symptoms are present but the criteria for paranoid, disorganized, or catatonic types have not been met. (DSM code 295.9/ICD code F20.3) Residual type: Where positive symptoms are present at a low intensity only. (DSM code 295.6/ICD code F20.5)

The ICD-10 defines two additional subtypes:

Post-schizophrenic depression: A depressive episode arising in the aftermath of a schizophrenic illness where some low-level schizophrenic symptoms may still be present. (ICD code F20.4)
Simple Schizophrenia: Insidious and progressive development of prominent negative symptoms with no history of psychotic episodes. (ICD code F20.6)

Differential Diagnosis
Psychotic symptoms may be present in several other mental disorders, including bipolar disorder, borderline personality disorder, drug intoxication and drug-induced psychosis. Delusions ("non-bizarre") are also present in delusional disorder, and social withdrawal in social anxiety disorder, avoidant personality disorder and schizotypal personality disorder. Schizotypal personality disorder has symptoms that are similar but less severe than those of Schizophrenia. Schizophrenia occurs along with obsessive-compulsive disorder (OCD) considerably more often than could be explained by chance, although it can be difficult to distinguish obsessions that occur in OCD from the delusions of Schizophrenia. A small number of people withdrawing from benzodiazepines experience a severe protracted withdrawal syndrome which can resemble Schizophrenia and be misdiagnosed as such.

A more general medical and neurological examination may be needed to rule out medical illnesses which may rarely produce psychotic Schizophrenia-like symptoms, such as metabolic disturbance, systemic infection, syphilis, HIV infection, epilepsy, and brain lesions. Stroke, multiple sclerosis, hyperthyroidism, hypothyroidism and dementias such as Alzheimer's disease, Huntington's disease, frontotemporal dementia and Lewy Body dementia may also be associated with Schizophrenia-like psychotic symptoms. It may be necessary to rule out a delirium, which can be distinguished by visual hallucinations; acute onset and fluctuating level of consciousness, and indicates an underlying medical illness. Investigations are not generally repeated for relapse unless there is a specific medical indication or possible adverse effects from antipsychotic medication. In children hallucinations must be separated from normal childhood fantasies.

There is no single laboratory or brain imaging test for Schizophrenia. Treatment professionals must rule out multiple factors such as brain tumors, possible medical conditions and other psychiatric diagnoses, such as bipolar disorder.

Individuals with Schizophrenia have two or more of the following symptoms occurring persistently. However, delusions or hallucinations alone can often be enough to lead to a diagnosis of Schizophrenia.

Positive symptoms are also known as “psychotic” symptoms because the person has lost touch with reality in certain ways.
 

Delusions or the belief in things not real or true. Hallucinations are hearing or seeing things that are not real. Disorganized speech expressed as an inability to generate a logical sequence of ideas. Negative symptoms refer to a reduction of a capacity, such as motivation. Emotional flatness or lack of expressiveness. Inability to start and follow through with activities. Lack of pleasure or interest in life. Cognitive symptoms pertain to thinking processes. Trouble with prioritizing tasks, memory and organizing thoughts. Anosognosia or “lack of insight” being unaware of having an illness. A diagnosis of Schizophrenia is made based on a full psychiatric evaluation, medical history, physical exam, and lab tests.

Psychiatric evaluation: The doctor or psychiatrist will ask a series of questions about you or your loved one's symptoms, psychiatric history, and family history of mental health problems.
Medical history and exam: Your doctor will ask about your personal and family health history. He or she will also perform a complete physical examination to check for medical issues that could be causing or contributing to the problem.
Laboratory tests: While there are no laboratory tests that can diagnose Schizophrenia, simple blood and urine tests can rule out other medical causes of symptoms. The doctor may also order brain-imaging studies, such as an MRI or a CT scan, in order to look for brain abnormalities associated with Schizophrenia.

 

Mental health professionals use the following criteria to diagnose Schizophrenia: The presence of two or more of the following symptoms for at least 30 days: 1. Hallucinations 2. Delusions 3. Disorganized speech 4. Disorganized or catatonic behavior 5. Negative symptoms (emotional flatness, apathy, lack of speech) Significant problems functioning at work or school, relating to other people, and taking care of oneself. Continuous signs of Schizophrenia for at least 6 months, with active symptoms (hallucinations, delusions, etc.) for at least 1 month. No other mental health disorder, medical issue, or substance abuse problem is causing the symptoms.