Is Schizophrenia Hereditary?

Is schizophrenia hereditary? It runs in families, but other factors count. Chances of siblings with the disease are not as high as scientists once thought. 

Schizophrenia is a severe psychotic disorder that shows up in about one percent of the population.

Is schizophrenia hereditary?

Although schizophrenia clearly runs in families, most people with a relative or even a sibling or parent with the condition will not develop the disorder. Estimates of how heritable it is are also declining.

Over the years, researchers have found that the chance of one twin suffering from schizophrenia if the other did was anywhere from 44 to 87 percent. The most common figure cited was 81 percent. One analysis of records for all people in Denmark found that your chance of suffering from schizophrenia if your parent did was 67 percent.

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The risk may be lower, however. A report from the Consortium on the Genetics of Schizophrenia Family Study in the United States concluded that the risk of schizophrenia was only 31 percent within a nuclear family. The group’s strategy is to identify endophenotypes — specific symptoms linked to genes.

Schizophrenia causes

Linking symptoms to genes is essential because the symptoms can be very different from one patient to another, with different genes, as well as other factors, at play.

Most people begin showing symptoms in their late teens or early 20s, but the signs can appear in your 40s or later. In those patients, one study indicates, the family history of illness was weaker. The patients were more likely to be female and have other illnesses and stresses, such as a history of unemployment.

Most likely, several small variations in genes combine to increase the risk of symptoms. Scientists know that experiences like infections in the womb or stress during childhood affect the outcome.

For example, a child with a family history of schizophrenia who is also neglected is more likely to become apathetic, losing interest in her usual activities and possibly ending up in bed for much of the day. If she’s not neglected, she might hear voices and show other symptoms but not become apathetic.

A small deletion in a region of chromosome 22 called 22q11 seems to contribute to a small percentage of cases, in which people may also have problems with their heart and immune system and a cleft palate.

Schizophrenia symptoms

Some people hear voices, or they may hallucinate visions, smells, or tactile sensations. They may also have delusions. A person with schizophrenia might believe he is Jesus Christ or that he’s being controlled by aliens.

Substance abuse, suicidal thoughts, and suicide attempts are more common in that group than in the general public.

People with schizophrenia sometimes become “flat” — with few facial expressions — or even completely unresponsive. They may develop movement problems, sometimes as a side effect of medication. They may also have depression and bipolar disorder, indicating schizoaffective disorder.

Family members of people with schizophrenia can get information and support through the National Alliance on Mental Illness and online forums.

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