Schizophrenia

Schizophrenia is a brain disorder affecting a person's thoughts, perceptions, and behavior, often leading to difficulty distinguishing between what is real and what is not (psychosis).

Overview

Schizophrenia is a disorder of the brain that affects a person's thoughts, perceptions, and behavior. Affected individuals may have difficulty distinguishing between what is real and what is not (psychosis).

Schizophrenia is typically diagnosed during late adolescence or early adulthood in men. The condition tends to be diagnosed slightly later in women. In a very small number of people, it can be diagnosed at a much younger age. The signs and symptoms of schizophrenia include hallucinations, which involve experiencing things that are not there. Hearing voices (auditory hallucination) is the most common type of hallucination that people with schizophrenia experience, but hallucinations may also involve sight, smell, or touch. Strongly held false beliefs (delusions) are also characteristic of schizophrenia. For example, affected individuals may be certain that they are a particular historical figure or that they are being plotted against or controlled by others.

Certain features of schizophrenia can make it difficult for affected individuals to function at school, at work, and in social settings. These features include odd and bizarre thinking and behavior (disorganization), unpredictable or inappropriate emotional responses, jumbled speech that cannot be understood, and neglect of personal hygiene. Affected individuals often have difficulty expressing emotions through facial expressions or body movements (flat affect). Cognitive impairment, which can include problems with memory, concentration, and problem-solving, may also make it difficult for people with schizophrenia to live or work independently. Substance abuse and suicidal thoughts and actions are more common in people with schizophrenia than in the general population.

Abnormal movements, such as tremors, facial tics, rigidity, and unusually slow movement (bradykinesia), are often seen in people with schizophrenia. In many cases these abnormal movements are the side effects of the medicines that are prescribed to help control the disorder. However, some affected individuals exhibit movement abnormalities before starting medications, suggesting that the abnormal movements may be part of the disorder itself.

Some people with schizophrenia also have a mood disorder or severe mood symptoms, such as depression or periods of extreme excitement (mania). Mood disorders primarily affect a person's emotional state.

Frequency

Schizophrenia is a common disorder that occurs all over the world. It affects people of all different ancestries and people in all cultures. Schizophrenia affects up to 1 percent of the population and may be more common in men than in women.

Causes

The exact causes of schizophrenia are not fully known. Studies suggest that genetic and environmental factors work together to increase the risk of developing schizophrenia.

The ways in which changes in specific genes (also called variants) contribute to the risk of developing schizophrenia is an active area of research. Many of the genes that are likely to be associated with schizophrenia affect the function of nerve cells (neurons). Some of the genetic variants that are associated with schizophrenia appear to impact the number, structure, or organization of the connections between neurons (synapses) where cell-to-cell communication takes place. Other genetic variants play a role in determining the amount or activity of certain chemical messengers (neurotransmitters) that relay signals from one neuron to another. Still others play a key role in regulating the activity of certain genes in the brain.

Common variants in hundreds of different genes, each with a small effect, likely increase a person's risk of developing schizophrenia. Less commonly, a rare variant in a specific gene may have a larger effect on the risk of developing schizophrenia. Similarly, rare deletions or duplications of large genetic regions in one of several chromosomes have also been found to increase the risk of developing schizophrenia. In some cases, schizophrenia occurs as part of a genetic syndrome that affects other organs and tissues in the body.

Environmental factors also appear to contribute to the risk of developing schizophrenia. These include complications during pregnancy or birth, exposure to certain maternal infections during pregnancy, and severe stress or trauma during childhood. Some studies show that young people who smoke marijuana, especially those who do it frequently, may have an increased risk of developing schizophrenia.

The genetic and environmental factors that increase the risk of developing schizophrenia likely work together to affect brain development and impair the communication between neurons.

Inheritance

Schizophrenia typically does not follow a clear-cut pattern of inheritance. Although family members of affected individuals have a higher risk of developing schizophrenia than members of the general public, most people with an affected relative will not develop the disorder.

When schizophrenia is part of a genetic syndrome, its risk follows the inheritance pattern of that syndrome.

Other Names

• SCZD