Merck Manual

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Carol Tamminga

, MD, UT Southwestern Medical Dallas

Reviewed/Revised Apr 2022 | Modified Oct 2022
Topic Resources

Schizophrenia is a mental disorder characterized by loss of contact with reality (psychosis), hallucinations (usually, hearing voices), firmly held false beliefs (delusions), abnormal thinking and behavior, reduced expression of emotions, diminished motivation, a decline in mental function (cognition), and problems in daily functioning, including work, social relationships, and self-care.

  • Neither the cause nor the mechanism of schizophrenia is known.

  • People may have a variety of symptoms, ranging from bizarre behavior and rambling, disorganized speech to loss of emotions and little or no speech to inability to concentrate and remember.

  • Doctors diagnose schizophrenia based on symptoms after they do tests to rule out other possible causes of psychosis.

  • Treatment involves antipsychotic drugs, training programs and community support activities, psychotherapy, and family education.

  • How well people do can be influenced by whether they take their medications as prescribed.

  • Early detection and early treatment improve long-term functioning.

Schizophrenia is a major health problem throughout the world. The disorder typically strikes young people at the very time they are establishing their independence and can result in lifelong disability and stigma. In terms of personal and economic costs, schizophrenia has been described as among the worst disorders afflicting humankind.

Overview of Schizophrenia

Schizophrenia affects about 1% of the population worldwide, men and women equally. In the United States, schizophrenia accounts for about 1 of every 5 Social Security disability days and 2.5% of all health care expenditures. Schizophrenia is more common than Alzheimer disease and multiple sclerosis.

Determining when schizophrenia begins (onset) is often difficult because unfamiliarity with symptoms may delay medical care for several years. The average age at onset is the early to mid-20s for men and slightly later for women. Onset during childhood Schizophrenia in Children and Adolescents Schizophrenia is a chronic disorder involving abnormal thoughts, perceptions, and social behavior and causing considerable problems with relationships and functioning. It lasts 6 months or more... read more is rare, but schizophrenia may begin during adolescence or, rarely, late in life.

Deterioration in social functioning can lead to a substance use disorder Substance Use Disorders Substance use disorders generally involve behavior patterns in which people continue to use a substance (for example, a recreational drug) despite having problems caused by its use. The substances... read more , poverty, and homelessness. People with untreated schizophrenia may lose contact with their families and friends and often find themselves living on the streets of large cities. The condition can last a lifetime, with poor psychosocial functioning throughout the lifetime in most cases.

Did You Know...

  • Schizophrenia is more common than Alzheimer disease and multiple sclerosis.

  • Various disorders, including thyroid disorders, brain tumors, seizure disorders, and other brain disorders, can cause symptoms similar to those of schizophrenia.

Causes of Schizophrenia

What precisely causes schizophrenia is not known, but current research suggests a combination of hereditary and environmental factors. Fundamentally, however, it is a biologic problem (involving molecular and functional changes in the brain), although certain external factors such as major life stresses or substance use Substance Use Disorders Substance use disorders generally involve behavior patterns in which people continue to use a substance (for example, a recreational drug) despite having problems caused by its use. The substances... read more can serve as triggers.

Factors that make people vulnerable to schizophrenia include the following:

  • A genetic predisposition

  • Problems that occurred before, during, or after birth, such as influenza in the mother during the 2nd trimester of pregnancy, lack of oxygen during delivery, a low birth weight, and incompatibility of the mother’s and infant’s blood type

  • Infections of the brain

  • Cannabis use in early teen years

People who have a parent or sibling with schizophrenia have about a 10% risk of developing the disorder, compared with a 1% risk among the general population. An identical twin whose co-twin has schizophrenia has about a 50% risk of developing schizophrenia. These statistics suggest that heredity is involved.

Symptoms of Schizophrenia

Schizophrenia may begin suddenly, over a period of days or weeks, or slowly and gradually, over a period of years. Although the severity and types of symptoms vary among different people with schizophrenia, the symptoms are usually sufficiently severe to interfere with the ability to work, interact with people, and care for oneself.

However, symptoms are sometimes mild at first (called the prodrome). People may simply appear withdrawn, disorganized, or suspicious. Doctors may recognize these symptoms as the beginning of schizophrenia, but sometimes doctors recognize them only in hindsight.

Schizophrenia is characterized by psychotic symptoms, which include delusions, hallucinations, disorganized thinking and speech, and bizarre and inappropriate behavior. Psychotic symptoms involve a loss of contact with reality.

In some people with schizophrenia, mental (cognitive) function declines, sometimes from the very beginning of the disorder. This cognitive impairment leads to difficulty paying attention, thinking in the abstract, and solving problems. The severity of cognitive impairment largely determines overall disability in people with schizophrenia. Many people with schizophrenia are unemployed and have little or no contact with family members or other people.

Symptoms may be triggered or worsened by stressful life events, such as losing a job or ending a romantic relationship. Drug use Illicit Drugs and Intoxicants , including use of marijuana, may trigger or worsen symptoms as well.

Overall, the symptoms of schizophrenia fall into four major categories:

  • Positive symptoms

  • Negative symptoms

  • Disorganization

  • Cognitive impairment

People may have symptoms from any or all categories.

Positive symptoms

Positive symptoms involve a distortion of normal functions. They include the following:

  • Delusions are false beliefs that usually involve a misinterpretation of perceptions or experiences. Also, people maintain these beliefs despite clear evidence that contradicts them. There are many possible types of delusion. For example, people with schizophrenia may have persecutory delusions, believing that they are being tormented, followed, tricked, or spied on. They may have delusions of reference, believing that passages from books, newspapers, or song lyrics are directed specifically at them. They may have delusions of thought withdrawal or thought insertion, believing that others can read their mind, that their thoughts are being transmitted to others, or that thoughts and impulses are being imposed on them by outside forces. Delusions in schizophrenia may be bizarre or not. Bizarre delusions are clearly implausible and not derived from ordinary life experiences. For example, people may believe that someone removed their internal organs without leaving a scar. Delusions that are not bizarre involve situations that could happen in real life, such as being followed or having a spouse or partner who is unfaithful.

  • Hallucinations involve hearing, seeing, tasting, or physically feeling things that no one else does. Hallucinations that are heard (auditory hallucinations) are by far the most common. People may hear voices in their head commenting on their behavior, conversing with one another, or making critical and abusive comments.

Negative symptoms

Negative symptoms involve a decrease in or loss of normal emotional and social functions. They include the following:

  • Reduced expression of emotions (blunted affect) involves showing little or no emotion. The face may appear immobile. People make little or no eye contact. People do not use their hands or head to add emotional emphasis as they speak. Events that would normally make them laugh or cry produce no response.

  • Poverty of speech refers to a decreased amount of speech. Answers to questions may be terse, perhaps one or two words, creating the impression of an inner emptiness.

  • Anhedonia refers to a diminished capacity to experience pleasure. People may take little interest in previous activities and spend more time in purposeless activities.

  • Asociality refers to a lack of interest in relationships with other people.

These negative symptoms are often associated with a general loss of motivation, sense of purpose, and goals.


Disorganization involves thought disorders and bizarre behavior:

  • Thought disorder refers to disorganized thinking, which becomes apparent when speech is rambling or shifts from one topic to another. Speech may be mildly disorganized or completely incoherent and incomprehensible.

  • Bizarre behavior may take the form of childlike silliness, agitation, or inappropriate appearance, hygiene, or conduct. Catatonia is an extreme form of bizarre behavior in which people maintain a rigid posture and resist efforts to be moved or, in contrast, move randomly.

Cognitive impairment

Cognitive impairment refers to difficulty concentrating, remembering, organizing, planning, and problem solving. Some people are unable to concentrate sufficiently to read, follow the story line of a movie or television show, or follow directions. Others are unable to ignore distractions or remain focused on a task. Consequently, work that involves attention to detail, involvement in complicated procedures, decision making, and understanding of social interactions may be impossible.


About 5 to 6% of people with schizophrenia commit suicide, about 20% attempt it, and many more have significant thoughts of suicide. Suicide is the major cause of premature death among young people with schizophrenia and is one of the main reasons why schizophrenia reduces average life span by 10 years.

Risk of suicide is increased in young men with schizophrenia, especially if they also have a substance use disorder Substance Use Disorders Substance use disorders generally involve behavior patterns in which people continue to use a substance (for example, a recreational drug) despite having problems caused by its use. The substances... read more . Risk is also increased in people who have depressive symptoms or feelings of hopelessness, who are unemployed, or who have just had a psychotic episode or been discharged from the hospital.

Risk of suicide is greatest for people who developed schizophrenia late in life and who were functioning well before it developed. Such people remain able to feel grief and anguish. Thus, they may be more likely to act in despair because they recognize the effects of their disorder. These people are also the ones with the best prognosis for recovery.

Did You Know...

  • About 5 to 6% of people with schizophrenia commit suicide.


Contrary to popular opinion, people with schizophrenia have only a slightly increased risk for violent behavior. Threats of violence and minor aggressive outbursts are far more common than seriously dangerous behavior. A very few severely depressed, isolated, paranoid people attack or murder someone whom they perceive as the single source of their difficulties (for example, an authority, a celebrity, their spouse).

People who are more likely to engage in significant violence include the following:

However, even taking risk factors into account, doctors find it difficult to accurately predict whether a given person with schizophrenia will commit a violent act.

Diagnosis of Schizophrenia

  • A doctor's evaluation, based on specific criteria

  • Laboratory and imaging tests to rule out other disorders

No definitive test exists to diagnose schizophrenia. A doctor makes the diagnosis based on a comprehensive assessment of a person’s history and symptoms.

Schizophrenia is diagnosed when both of the following are present:

  • Two or more characteristic symptoms (delusions, hallucinations, disorganized speech, disorganized behavior, negative symptoms) persist for at least 6 months.

  • These symptoms cause significant deterioration in work, school, or social functioning.

Information from family members, friends, or teachers is often important in establishing when the disorder began.

Laboratory tests are often done to rule out a substance use disorder Substance Use Disorders Substance use disorders generally involve behavior patterns in which people continue to use a substance (for example, a recreational drug) despite having problems caused by its use. The substances... read more or an underlying medical, neurologic, or hormonal disorder, that can have features of psychosis. Examples of such disorders include brain tumors, temporal lobe epilepsy, thyroid disorders, autoimmune disorders, Huntington disease, liver disorders, side effects of drugs, and vitamin deficiencies. Testing for substance use disorder is sometimes done.

Imaging tests of the brain, such as computed tomography (CT) or magnetic resonance imaging (MRI), may be done to rule out a brain tumor. Although people with schizophrenia have brain abnormalities that may be seen on CT or MRI, the abnormalities are not specific enough to help in diagnosing schizophrenia.

Prognosis for Schizophrenia

Early detection and early treatment have become the guiding principles for managing schizophrenia. The sooner treatment is started, the better the outcome.

For people with schizophrenia, the prognosis depends largely on adherence to drug treatment. Without drug treatment, 70 to 80% of people have another episode within the first year after diagnosis. Drugs taken continuously can reduce this percentage to about 30% and can lessen the severity of symptoms significantly in most people. After discharge from a hospital, people who do not take prescribed drugs are very likely to be readmitted within the year. Taking drugs as directed dramatically reduces the likelihood of being readmitted.

Despite the proven benefit of drug therapy, half of people with schizophrenia do not take their prescribed drugs. Some do not recognize their illness and resist taking drugs. Others stop taking their drugs because of unpleasant side effects. Memory problems, disorganization, or simply a lack of money prevents others from taking their drugs.

Adherence is most likely to improve when specific barriers are addressed. If side effects of drugs are a major problem, a change to a different drug may help. A consistent, trusting relationship with a doctor or other therapist helps some people with schizophrenia to accept their illness more readily and recognize the need for adhering to prescribed treatment.

Over longer periods, the prognosis varies, roughly as follows:

  • One third of people achieve significant and lasting improvement.

  • One third achieve some improvement with intermittent relapses and residual disabilities.

  • One third experience severe and permanent incapacity.

Only about 15% of all people with schizophrenia are able to function as well as they could before schizophrenia developed.

Factors associated with a better prognosis include the following:

  • Sudden onset of symptoms

  • Older age when symptoms start

  • A good level of skills and accomplishments before becoming ill

  • Only slight cognitive impairment

  • Presence of only a few negative symptoms (such as reduced expression of emotions)

  • A shorter time between the first psychotic episode and treatment

Factors associated with a poor prognosis include the following:

  • Younger age when symptoms start

  • Problems functioning in social situations and at work before becoming ill

  • A family history of schizophrenia

  • Presence of many negative symptoms

  • A longer time between the first psychotic episode and treatment

Men have a poorer prognosis than women. Women respond better to treatment with antipsychotic drugs.

Treatment of Schizophrenia

  • Antipsychotic drugs

  • Psychotherapy

  • Coordinated specialty care

Generally, treatment of schizophrenia aims

  • To reduce the severity of psychotic symptoms

  • To prevent the recurrence of symptomatic episodes and the associated deterioration in functioning

  • To provide support and thus enable people to function at the highest level possible

Early detection and early treatment are important. The earlier treatment begins, the better the outcome.

Antipsychotic drugs, rehabilitation and community support activities, and psychotherapy are the major components of treatment. Teaching family members about the symptoms and treatment of schizophrenia (family psychoeducation) helps provide support for them and helps health care practitioners maintain contact with the person who has schizophrenia.

Coordinated specialty care, which includes resilience training, personal and family therapy, addressing cognitive dysfunction, and supported employment, is an important aspect of psychosocial recovery.

Antipsychotic drugs

Antipsychotic drugs Antipsychotic Drugs Psychosis refers to symptoms such as delusions, hallucinations, disorganized thinking and speech, and bizarre and inappropriate motor behavior that indicate loss of contact with reality. A number... read more can be effective in reducing or eliminating symptoms, such as delusions, hallucinations, and disorganized thinking. After the immediate symptoms have cleared, the continued use of antipsychotic drugs substantially reduces the probability of future episodes. However, antipsychotic drugs have significant side effects, which can include drowsiness, muscle stiffness, tremors, involuntary movements (for example, tardive dyskinesia), weight gain, and restlessness. The newer antipsychotic (second-generation) drugs, which are prescribed most often, are less likely to cause muscle stiffness, tremors, and tardive dyskinesia than conventional (first-generation) antipsychotic drugs.

Rehabilitation programs and community support activities

Rehabilitation and support programs, such as on-the-job coaching, are directed at teaching people the skills they need to live in the community, rather than in an institution. These skills enable people with schizophrenia to work, shop, care for themselves, manage a household, and get along with others.

Community support services provide services that enable people with schizophrenia to live as independently as possible. These services include a supervised apartment or group home where a staff member is present to ensure that a person with schizophrenia takes drugs as prescribed or to help the person with finances. Or a staff member may visit the person's home periodically.

Hospitalization may be needed during severe relapses, and involuntary hospitalization may be needed if people pose a danger to themselves or others. However, the general goal is to have people live in the community.

A few people with schizophrenia are unable to live independently, either because they have severe, persistent symptoms or because drug therapy has not been effective. They usually require full-time care in a safe and supportive setting.

Support and advocacy groups, such as the National Alliance on Mental Illness, are often helpful to families.


Generally, psychotherapy does not lessen the symptoms of schizophrenia. However, psychotherapy can be helpful by establishing a collaborative relationship between people with schizophrenia, their family members, and the doctor. That way, people may learn to understand and manage their disorder, to take antipsychotic drugs as prescribed, and to manage stresses that can aggravate the disorder. A good doctor-patient relationship is often a major determinant of whether treatment is successful.

If people with schizophrenia live with their families, they and their family members may be offered psychoeducation. This training provides people and their family members with information about the disorder and about ways to manage it—for example, by teaching them coping skills. This training can help prevent relapses.

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