Having a sibling with schizophrenia increases risk for disorder 10-fold

Individuals with a sibling with schizophrenia were approximately ten times more likely to develop the disorder and had increased risk for bipolar disorder and other mental health disorders, according to findings presented at the European College of Neuropsychopharmacology Congress.

“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 [10 times the] risk of developing schizophrenia, and similar risks once a sibling has developed bipolar disorder,” study researcher Mark Weiser MD, of Sheba Medical Center, Ramat Gan, Israel, said in a press release.

To determine risk for hospitalization due to psychiatric disorders among siblings of individuals with schizophrenia or bipolar disorder, researchers used the Israeli Psychiatric Hospitalization Registry and the Israeli Population Registry to identify 6,111 individuals hospitalized with a diagnosis of schizophrenia, schizoaffective disorder, bipolar disorder or unipolar depression and 74,988 age- and gender-matched controls.

Siblings of probands with broadly defined schizophrenia had significantly higher risk for hospitalization for broadly defined schizophrenia (OR = 9.41; 95% CI, 6.86-12.9), narrowly defined schizophrenia (OR = 6.83; 95% CI, 4.55-10.27), schizoaffective disorder (OR = 8.51; 95% CI, 4.37-16.59) and bipolar disorder (OR = 7.66; 95% CI, 2.57-22.88), compared with controls.

Siblings of probands with narrowly defined schizophrenia had increased risk for broadly defined schizophrenia (OR = 10.67; 95% CI, 6.9-16.48), schizoaffective disorder (OR = 10.31; 95% CI, 3.63-29.32) and narrowly defined schizophrenia (OR = 7.83; 95% CI, 4.32-14.2), compared with controls.

Siblings of probands with bipolar disorder had significantly higher risk for hospitalization for broadly defined schizophrenia (OR = 4.2; 95% CI, 1.57-11.26) and other psychiatric disorders (OR = 7.56; 95% CI, 2.52-22.69), compared with controls. They were also more likely to be hospitalized for bipolar disorder (OR = 8.41; 95% CI, 0.76-92.9), but the association did not achieve sufficient statistical power.

Siblings of probands with unipolar depression had significantly higher risk for hospitalization for broadly and narrowly defined schizophrenia (OR = 6.24) and other psychiatric disorders (OR = 9.71; 95% CI, 2.5-37.72).

“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,” Weiser said in the release. – by Amanda Oldt

Reference:

Jacobs A, et al. Risk of psychiatric disorders in siblings of patients diagnosed with schizophrenia or affective disorders. Presented at: European College of Neuropsychopharmacology Congress; September 17-20, 2016; Vienna.

Disclosure: The researchers report no relevant financial disclosures.