Introduction
The development of schizophrenia, it is believed, is based on a multifactorial genesis. This means that several different factors can or must interact to trigger the clinical picture of schizophrenia. One of these building blocks is genetics.
However, unlike other diseases, such as trisomy 21, it is not possible to identify a precise genetic change that leads to the development of this disease. Rather, it is assumed that certain genetic changes lead to increased vulnerability or susceptibility. On this basis, external factors can then favour the development of the disease. Thus, schizophrenia is a hereditary disease, but only in the sense of an increased risk of developing the disease.
How often is schizophrenia passed from parents to children?
Over the entire population, the lifetime risk of developing schizophrenia is approximately 1%. However, the risk can increase significantly if one or even both parents are affected by the disease. It increases more than 10-fold if one of the two parents is affected.
If mother and father are affected at the same time, the risk of the disease is already 46%. It is currently assumed that about 80% of cases are due to genetic changes. Thus, the inheritance of predisposing factors in the development plays a leading role. It is not yet fully understood in which genes a mutation must be present.
How often is schizophrenia transmitted to the grandchild?
Even if a person’s children do not suffer from schizophrenia, the risk of developing the disease is increased among grandchildren. Studies have shown that the risk is 5 times higher than in the general population. This corresponds to a lifetime risk of 5%. However, this already represents a risk halved compared to the risk of illness for parents.
Is there an early test to see if the schizophrenia has been transmitted?
Despite great efforts, research has not yet been able to find a concrete gene that leads to schizophrenia in a mutation. Although there are now a number of genes that are considered suspicious, no clinical proof has yet been found. In addition to these suspected genes, there are a number of other genetic diseases that have a significantly increased risk of developing schizophrenia.
Examples of these are Fra(X) syndrome or microdeletion syndrome 22q11, in which other severe symptoms, such as mental retardation, occur alongside schizophrenia. A test for the early detection of schizophrenia is therefore not useful, as it is not yet clear what it is supposed to look for. Genetic counseling for schizophrenia is based on population studies, which can indicate the risk of developing schizophrenia if, for example, a relative is affected. However, we are still far from a concrete understanding of this relationship.
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