High rates of mood disorders in patients with chronic idiopathic eosinopenia

Background: Mood disorders (MD) are multifactorial disorders. Identifying new biomarkers for the early diagnosis of MD and predicting response to treatment is currently a significant research topic. Both eosinopenia and MD are associated with increased activity of the hypothalamic-pituitary-adrenal axis. The present study, therefore, used a clear definition of chronic idiopathic eosinopenia (CIE) to determine the rate of MD in a large cohort of individuals with CIE. Methods: This retrospective population-based, case-control study uses data of seven consecutive years from the database of Leumit Health Services (LHS) - a nationwide health maintenance organization in Israel. Results: Participants were 13928 LHS members with CIE and 27858 negative controls. The CIE group exhibited significantly higher rates of MD than the control group throughout the whole study period, except for atypical depressive disorder at baseline. Conclusions: CIE might be associated with a higher prevalence of MD. Further basic research should elucidate the pathophysiologic mechanisms linking CIE and MD.