In our review, we noticed that IL-2 decreased with the administration of the SSRIs escitalopram [191,203] (one study in patients with moderate depression, another study in patients with MDD), fluoxetine (one study, patients with MDD) [203], sertraline (one study, patients with unipolar depression) [204], as well as with ketamine (one study, patients with treatment-resistant depression) [195]. Here, IL2 is linked to major depressive disorder.