IL6 and generalized anxiety disorder: This immune hypothesis of GAD development is further potentiated by findings from several clinical studies that reported that GAD patients showed significantly higher levels of pro-inflammatory cytokines ( IL-1Ra, IL-1, IL-6, TNF-α, etc.)compared to healthy controls (HCs) [19–28] along with decreased levels of anti-inflammatory cytokines, including IL-4 and IL-10 [25].