Antioxidant status and its association with elevated depressive symptoms among US adults: National Health and Nutrition Examination Surveys 2005-6

We examined the relationship of elevated depressive symptoms with antioxidant status. Cross-sectional data from the National Health and Nutrition Examination Surveys 2005-6 on US adults aged 20-85 years were analysed. Depressive symptoms were measured using the Patient Health Questionnaire with a score cut-off point of 10 to define 'elevated depressive symptoms'. Serum antioxidant status was measured by serum levels of carotenoids, retinol (free and retinyl esters), vitamin C and vitamin E. The main analyses consisted of multiple logistic and zero-inflated Poisson regression models, taking into account sampling design complexity. The final sample consisted of 1798 US adults with complete data. A higher total serum carotenoid level was associated with a lower likelihood of elevated depressive symptoms with a reduction in the odds by 37% overall with each SD increase in exposure, and by 34% among women (P<0.05). A dose-response relationship was observed when total serum carotenoids were expressed as quartiles (Q(4 (1.62-10.1 mu mol/l)) v. Q(1 (0.06-0.86 mu mol/l)): OR 0.41; 95% CI 0.23, 0.76, P<0.001; P for trend=0.035), though no significant associations were found with the other antioxidant levels. Among carotenoids, beta-carotene (men and women combined) and lutein + zeaxanthins (women only, after control for dietary lutein + zeaxanthin intake and supplement use) had an independent inverse association with elevated depressive symptoms among US adults. None of the other serum antioxidants had a significant association with depressive symptoms, independently of total carotenoids and other covariates. In conclusion, total carotenoids (mainly beta-carotene and lutein + zeaxanthins) in serum were associated with reduced levels of depressive symptoms among community-dwelling US adults.