Full description of Schizophrenia. Definition, signs, symptoms, and causes of Schizophrenia.

Full description of Schizophrenia. Definition, signs, symptoms, and causes of Schizophrenia.

Description of Schizophrenia

Schizophrenia has been described as among the worst disorders afflicting humankind. Schizophrenia is a disabling mental illness where disordered thinking disturbs an individual's ability to function normally. The disorder typically strikes young people at the very time they are establishing their independence and can result in lifelong disability and stigma. The average age for the onset of schizophrenia is 18 for men and 25 for women. Onset in childhood or early adolescence is uncommon as is onset late in life.

People with schizophrenia sometimes hear voices others don't hear, believe that others are broadcasting their thoughts to the world, or become convinced that others are plotting to harm them. These experiences can make them fearful and withdrawn and cause difficulties when they try to have relationships with others.

People diagnosed with schizophrenia are likely to be diagnosed with comorbid conditions, including clinical depression and anxiety disorders; the lifetime prevalence of substance abuse is typically around 40%. Social problems, such as long-term unemployment, poverty and homelessness, are common and life expectancy is decreased. The average life expectancy of people with the disorder is 10 to 12 years less than those without, owing to increased physical health problems and a high suicide rate.

Diagnostic Criteria for Schizophrenia

Characteristic symptoms of Schizophrenia: 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 (false beliefs)
  • hallucinations (usually, hearing voices)
  • disorganized speech (e.g., frequent derailment or incoherence)
  • grossly disorganized or catatonic behavior
  • negative symptoms, i.e., affective flattening (restricted range of emotions), alogia, or avolition. Note: Only one 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.

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).

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 the first criteria (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 the first criteria present in an attenuated form (e.g., odd beliefs, unusual perceptual experiences).

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.

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.

Relationship to a Pervasive Developmental Disorder: 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).

Causes of Schizophrenia

The precise cause of schizophrenia remains unknown, but there's evidence of a genetic predisposition. In the general population, there's a 1% chance of someone developing schizophrenia. The risk is increased if a child has a schizophrenic parent (10%) or identical twin (50 %). While schizophrenia runs in families, about 60% of schizophrenics have no family members with the disorder.

Researchers have also uncovered environmental factors that may trigger schizophrenia in people who are genetically predisposed to the disorder. Stress, either during pregnancy or at a later stage of development may be a key risk factor. High levels of stress are believed to trigger schizophrenia by increasing the body's production of the hormone cortisol.

Research points to several stress-inducing environmental factors that may be involved in schizophrenia, including:

  • Prenatal exposure to a viral infection
  • Low oxygen levels during birth (from prolonged labor or premature birth)
  • Exposure to a virus during infancy
  • Early parental loss or separation
  • Physical or sexual abuse in childhood

A brain chemical imbalance involving dopamine and glutamate may also play a role in developing schizophrenia. Scientists have also discovered that people with schizophrenia have abnormal brains; less brain tissue and very low activity in the frontal lobe, the area of the brain responsible for planning, reasoning, and decision-making.

For comprehensive information on schizophrenia and other thought disorders, visit the Thought Disorders Community.

Sources: 1. American Psychiatric Association. (1994). Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. Washington, DC: American Psychiatric Association. 2. Merck Manual, Home Edition for Patients and Caregivers, last revised 2006. 3. NIMH website, "What Causes Schizophrenia", June 2008. 4. Brown S, Barraclough B, Inskip H (2000). "Causes of the excess mortality of schizophrenia". British Journal of Psychiatry 177: 212-7.

APA Reference
Writer, H. (2009, January 3). Schizophrenia, HealthyPlace. Retrieved on 2019, October 20 from

Last Updated: July 5, 2019

Medically reviewed by Harry Croft, MD

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