Risk of hospitalization for psychiatric disorders among siblings and parents of probands with psychotic or affective disorders: A population-based study

Relatives of people diagnosed with psychotic and affective disorders have a higher risk of developing psychiatric disorders compared to the general population. This study examined the risk of hospitalization for psychiatric disorders among siblings and parents of patients affected with major psychiatric disorders. In this large population-based case-control study, 17,895 siblings and parents of 7671 hospitalized subjects with a diagnosis of narrowly defined schizophrenia (SZ), broadly defined SZ, schizoaffective disorder (SAD), bipolar disorder (BD) or unipolar depression (UD) were identified from the Israeli Psychiatric Hospitalization Registry and compared to 71,580 age and gender-matched controls from the Israeli Population Registry. Results indicated that siblings of people diagnosed with broadly defined SZ had a significantly higher risk of hospitalization for broadly (OR=11.06, 95% CI=7.93-15.41) and narrowly defined SZ (OR=10.59, 95% CI=6.8-16.33), SAD (OR=9.69, 95% CI=4.76-19.73), BD (OR=7.46, 95% CI=21.8-25.52), UD (OR=2.84, 95% CI=1.01-8.00), and other psychiatric disorders (OR=1.85, 95% CI=1.16-2.93), compared to controls. Siblings of patients with BD had a significantly higher risk of hospitalization for broadly defined SZ (OR=2.92, 95% CI=1.11-7.71) and for other psychiatric disorders (OR=6.67, 95% CI=2.17-20.50), compared to controls. Parents of probands with SZ were at significantly increased risk for all disorders examined, except for UD and ¨other psychiatric disorders¨, which was not significant in parents of probands with BD. This large, population-based study provides evidence for common genetic risk across different psychiatric disorders.