The elevated IL-6 levels in untreated and Roflumilast-treated depressed groups, despite being lowered in Roflumilast-treated depressed group compared to the untreated depressed ones could be explained by chronic stress-induced activation of inflammatory pathways triggering the development of depression, thus depressive disorders could partly be explained by some inflammatory mediators, namely increased IL-6. Here, IL6 is linked to major depressive disorder.