Sibling risk of anxiety disorders based on hospitalizations in Sweden.

Aims: This study used nationwide hospital records to examine sibling risk of any type of anxiety disorder in Sweden over a 40-year period. Methods: This study, carried out between 1 January 1968 and 31 December 2007, of the entire population of Sweden, linked information on family relationships from the nationwide Multi-Generation Register with information from the nationwide Swedish Hospital Discharge Register on first diagnosis of anxiety disorder. A total of 42 602 persons hospitalized for anxiety disorders and 2093 affected siblings were identified. Standardized incidence ratios (SIR) were calculated by comparing risk in siblings of persons hospitalized for anxiety disorders with risk in persons whose siblings had no hospital diagnosis of anxiety disorders. Results: The sibling risk was 2.26, which was independent of sex and age differences between siblings. The SIR was highest in siblings