CXCL8 and major depressive disorder: Our study aimed to 1) describe the prevalence of depression among a community sample of adolescents and the severity of their depressive symptoms, and 2) examine the associations of pro-inflammatory biomarkers TNF-α, IL-1β, IL-6, and IL-8 with both severity of depressive symptoms and an established clinical cutoff for depression that suggests a need for diagnostic referral.