Stratification by CRP level impacted odds of depression among exclusive e-cigarette users as follows: among e-cigarette users with CRP < 8 mg/L the OR = 1.91 (95% CI: 0.78, 4.69), whereas exclusive e-cigarette users with elevated CRP ≥ 8 mg/L were 5 times more likely to be depressed than the non-smoking/never-vaping reference group with elevated CRP (OR = 5.09, 95% CI: 1.44, 18.02; uncorrected p-value < 0.05, FDR adjusted p-value = 0.051). The gene discussed is CRP; the disease is major depressive disorder.