Background: Major depressive disorder (MDD) is associated with high mortality and morbidity
rates, and currently, approximately 340 million people worldwide suffer from depression at
some point in life. In view of the growing socio-economic and clinical impact, several studies have focused
on the etiopathology of MDD, suggesting that not only the monoaminergic system but also other
brain mechanisms may be involved in the pathophysiology of MDD. Recent studies have shown a link
between inflammation and MDD and have also demonstrated that antidepressants and antiinflammatory
drugs can act to reduce inflammation, thereby improving depressive symptoms. Animal
models of depression are indispensable for studying the pathophysiology of this disorder and new
treatments for it. Further, studies have shown that rodent models of depression are also associated with
elevated levels of inflammation in the periphery and brain.
Objective: This review will highlight the role of immune inflammation in MDD and the significance
of immune system modulators with antidepressant effects in the treatment of MDD, based on studies
using animal models of depression.