Risk of bipolar disorder among adolescents with allergic rhinitis: A nationwide longitudinal study.

BACKGROUND Previous studies have suggested an immunological dysfunction in bipolar disorder, but none has investigated the temporal association between allergic rhinitis (AR) and bipolar disorder. METHODS Using Taiwan National Health Insurance Research Database, 9506 adolescents aged 12-18 years with allergic rhinitis were enrolled between 2000 and 2008 and compared to 38,024 age-and gender-matched (1:4) control groups. Subjects of bipolar disorder that occurred up to the end of follow-up (December 31, 2011) were identified. RESULTS Adolescents with AR had a significantly higher incidence of developing bipolar disorder (0.77 vs. 0.18 per 1000 person-years, p<0.001) during the follow-up period than the controls. Adolescents with AR had an increased risk (hazard ratio [HR]: 4.62, 95% confidence interval [CI]: 3.17-6.75) of developing bipolar disorder in their later life compared to the control group after adjusting for demographic data and comorbid allergic diseases. DISCUSSION This is the first study showing a temporal association between AR and bipolar disorder, in that patients who had AR in adolescence exhibited an increased risk of developing bipolar disorder in later life. Further study would be required to investigate the underlying mechanism about this association.