Fig. 1From: Association between serum copper, zinc, and selenium concentrations and depressive symptoms in the US adult population, NHANES (2011–2016)Flow chart for recruiting participants for this study, NHANES (2011–2016). Abbreviations: NHANES, National Health and Nutrition Examination Survey; n, sample size; PHQ-9, the Patient Health Questionnaire-9 ItemsBack to article page