Schizophrenia

Genes are tiny parts of cells that carry traits (an individual's personal characteristics) from parents to children. They are like a “recipe” for a new person. People inherit genes from their parents, and traits that are controlled by genes are called inherited traits.

For example, the color of your eyes is determined by your genes and is, therefore, said to be inherited. Many researchers believe that schizophrenia might be caused, at least partly, by inherited genes that increase a person's risk for developing the disorder.

Studies have shown that schizophrenia runs in families. That is, relatives of schizophrenia sufferers are more likely to develop the condition than people from families that are free of schizophrenia. Furthermore, closely related relatives, who share more of the same genes with the schizophrenia sufferer than do more distant relatives, are even more likely to develop the disorder.

Identical vs. Fraternal Twins

Identical twins share all of the same genes, whereas fraternal (nonidentical) twins share only about half of the same genes. This fact has allowed scientists to find out important information about the role of genes in causing schizophrenia.

Studies show that a person whose identical twin has schizophrenia is much more likely to develop schizophrenia than a person whose nonidentical twin has schizophrenia. The risk for schizophrenia for the identical twin is about 40 to 60 percent, and the risk for the nonidentical twin is about 20 percent. This means that the more genes a person shares with a schizophrenia sufferer, the greater his or her risk is for developing schizophrenia. The risk for more distant relatives, such as grandchildren or nieces and nephews of people with schizophrenia, is less than 10 percent.