TNF and major depressive disorder: Numerous clinical studies have reported abnormal inflammation profiles in both the brain and peripheral tissues of patients with MDD.43 Consistent with this, our data showed significantly elevated serum TNF-α levels in MDD patients, in line with a recent meta-analysis confirming higher TNF-α levels in patients with MDD in comparison with healthy subjects.44 At the molecular level, a genome-wide association study identified TNF-α polymorphisms associated with MDD,45 suggesting a potential role of TNF-α in the pathophysiology of the disorder.