FIGURE 1.

Adjusted odds ratios (with 95% CI) of major serum antioxidant level (expressed as quartiles, Q₂, Q₃, Q₄ vs. Q₁) and elevated depressive symptoms among US adults, uncontrolled for dietary antioxidant intakes or supplement use; NHANES 2005–06

Notes: CI=Confidence Interval. Ranges for each antioxidant quartile is as follows in μmol/L: Retinol+retinyl esters (Q₁: 0.07–1.7; Q₂: 1.7–2.1; Q₃: 2.1–2.5; Q₄: 2.5–8.9); Total carotenoids (Q₁: 0.06–0.86; Q₂: 0.86–1.18; Q₃: 1.18–1.62; Q₄: 1.62–10.1); Vitamin E (Q₁: 0.2–26.7; Q₂: 21.7–27.3; Q₃: 27.4–35.9; Q₄: 35.9–303.8); Vitamin C (Q₁: 0.6–34.6; Q₂: 35.2–54.5; Q₃: 55.1–70.4; Q₄: 71.0–274.2). Analyses were based on multiple logistic regression models that included all antioxidant exposures simultaneously adjusted for socio-demographic factors: Lifestyle and health-related factors (smoking status, BMI, physical activity: Mets.hr.wk⁻¹, recoded as “0–<5”; “5–10”; “>10”, history of selected chronic conditions (i.e. type 2 diabetes, CVD and cancer)), anti-depressant use and dietary intakes (total energy intake, alcohol, n-3 PUFA), serum levels folate, total homocysteine, vitamin B-12, 25-hydroxyvitamin D and serum total cholesterol, anti-depressant use, and the inverse mills ratio, 2-stage Heckman selection model.

*P<0.05; ^┼P<0.001 for null hypothesis that Log_e(OR)=0.