Interleukin-1β is associated with depressive episode in major depression but not in bipolar disorder.

Our work was sought to investigate possible changes in peripheral levels of interleukin-1β (IL-1β) according to the diagnosis of major depression (MD) and bipolar disorder (BD) and in different mood episodes. This is a cross-sectional nested in a population-based study comparing 240 young adults (80 controls, 80 MD and 80 BD), balanced for age and gender. Serum levels of IL-1β were significantly higher in MD when compared to control or BD subjects. In addition, when divided by current mood episode, MD subjects in current depression presented higher IL-1β levels than controls. No differences in IL-1β levels were found between different episodes of BD (euthymic, depressed, mania or mixed). Moreover, the use of psychiatric medication was very low in our sample and not associated with changes in IL-1β levels. In conclusion, increased peripheral IL-1β might be a useful marker associated with a depressive episode in the context of MD.