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Harvard Medical School

Schizophrenia

What Is It?

Schizophrenia is a chronic (long-lasting) mental illness that is difficult to define and is easily misunderstood. Although symptoms may vary widely, people with schizophrenia frequently have a hard time recognizing reality, thinking logically and behaving naturally in social situations. Schizophrenia is surprisingly common, affecting 1 in every 100 people worldwide.

Experts believe schizophrenia results from a combination of genetic and environmental influences. The chance of having schizophrenia is 10% if an immediate family member (a parent or sibling) has the illness. The risk swells to as much as 65% for those who have an identical twin with schizophrenia.

Scientists have identified several genes that increase the risk of getting this illness. In fact, with 20 or 30 or more problem genes being investigated, schizophrenia can be seen as several illnesses rather than one. These genes probably affect the way the brain develops and how nerve cells communicate with one another. In a vulnerable person, a stress (such as a toxin, an infection or a nutritional deficiency) may trigger the illness during critical periods of brain development.

Although the biology has yet to be worked out in detail, mental health professionals should eventually acquire tools to identify the people most at risk for developing schizophrenia. This kind of knowledge should help individuals minimize the negative impact of the illness.

Schizophrenia may start as early as childhood and last throughout life. People with this illness periodically have difficulty with their thoughts and their perceptions. They may withdraw from social contacts, and if not treated, they will display more symptoms and function less well as time passes.

Schizophrenia is one of the "psychotic" disorders. Psychosis can be defined as the inability to recognize reality. It can include such symptoms as delusions (false beliefs), hallucinations (false perceptions), and disorganized speech or behavior. Psychosis is a feature of many mental disorders. In other words, not all people who are psychotic have schizophrenia.

Symptoms in schizophrenia are described as either "positive" or "negative." Positive symptoms are psychotic symptoms such as delusions, hallucinations and disorganized behavior. Negative symptoms are the tendency toward restricted emotions, flat speech and the inability to start productive activity.

In addition to positive and negative symptoms, many people with schizophrenia also have cognitive symptoms (problems with their intellectual functioning). They may have trouble with "working memory." That is, they have trouble keeping recently learned information in mind in order to use it, for example, for making plans or for organizing themselves. These problems can be very subtle, but in many cases may account for why a person with schizophrenia has such a hard time managing day-to-day life.

Schizophrenia can be marked by a steady deterioration of logical thinking, social skills and behavior. These problems can interfere with personal relationships or functioning at work. Self-care can also suffer.

As people with schizophrenia realize what it means to have the disease, they may become depressed. People with schizophrenia are therefore at greater than average risk of committing suicide. Family members and health care professionals need to stay alert to this possibility.

People with schizophrenia are also at more risk for developing substance abuse problems. People who drink and use illicit drugs have more difficulty adhering to treatment. Schizophrenia is associated with higher rates of smoking than in the general population, leading patients with this illness to have more health problems. Schizophrenia has the following subtypes:

• Paranoid. This is perhaps the best known subtype because people tend to wrongly believe that paranoia and schizophrenia always go together "paranoid schizophrenic"). But only a limited number of people with schizophrenia have paranoid symptoms. What characterizes the paranoid type is the presence of delusions, whereas disorganization and emotional flatness are not prominent. In this subtype, the delusions may not even be paranoid in content; instead, they may have non-paranoid themes, such as religious delusions or "delusions of grandeur".

• Disorganized. Speech or behavior may be disorganized, and emotional responses are blunted or unusual.

• Catatonic. The person may become immobile or agitated, become peculiarly negative or mute, or display unusual behavior or speech.

• Undifferentiated. The person has psychotic (positive) symptoms, but they do not clearly fit into any of the above categories.

• Residual. The main symptoms are negative symptoms without any of the major psychotic symptoms seen in the other subtypes.