What is the risk of developing a mental disorder if a brother or sister has the condition? Now a large survey using data from all patients hospitalized in psychiatric wards in Israel, and their siblings, has given some answers: having a sibling with schizophrenia increases your risk of developing the condition by a factor of x10, with increased risks of developing bipolar disorder and other mental disorders. Similar increases are seen with siblings of patients with bipolar disorder.
This is the first study to assess risk of developing any psychiatric diagnosis in siblings of all patients hospitalized for any type of mental disorder in an entire population, and is presented at the ECNP neuroscience congress in Vienna.
The lifetime chance of suffering a mental disorder is extremely high. It is estimated that each year 38.2% of the EU population suffers from a mental disorder, corresponding to 164.8 million persons affected (1). It is known that siblings of patients with major mental disorders have an increased risk of suffering from the same disorder, but until now the risks have not been quantified
Now an international team has examined the rates of mental disorders in the families of 6111 Israeli patients who had been hospitalised with schizophrenia, bipolar disorder, or depression. They compared them to over 74,000 controls, age-and gender matched controls, taken from the Israeli Population Registry, which records all births, deaths, marriages and divorces in the country. By comparing the relative rates of mental disorders, they were able to show just how much more siblings are at risk of the same, and also other mental health conditions.
If a brother or sister has schizophrenia, a sibling has x10 greater chance of themselves suffering from schizophrenia. They also have x6 to x8 increased chance of suffering from schizoaffective disorder, and x7 to x20 greater risk of suffering from bipolar disorder than the general population.
If a brother or sister suffers from bipolar disorder, then their siblings have x4 greater chance of suffering from bipolar disorder, schizophrenia, and other psychiatric disorders.
According to lead researcher, Prof. Mark Weiser MD
“This is a large study which allows us to put meaningful figures on the risks of developing mental disorders after they have arisen in a brother or sister. The figures are quite striking, with x10 risk of developing schizophrenia, and similar risks once a sibling has developed bipolar disorder.
These results are important clinically, as they encourage mental health workers to be aware of the increased risk of psychiatric disorders in siblings of patients. These results can also be used by researchers studying the genetic underpinnings of mental disorders, as they indicate that the same genes might be associated with increased risk for various psychiatric disorders.”
Figure 1. The risk of developing mental disorders in siblings of patients with schizophrenia compared to the general population (age and gender-matched controls).
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