The Relationship between Iron Status and Depression in Non-Inflamed Women

Abstract

Depression is a debilitating condition which has been increasing in prevalence in the United States. Epidemiological studies suggest that the pathophysiology of depression may be related to nutrient deficiencies. One nutrient of particular interest is iron. Iron deficiency, with or without anemia, is a major worldwide health concern. Iron is involved in several biochemical pathways necessary for maintaining healthy mood. However, the existing literature has presented mixed findings regarding the relationship between iron status as measured by serum ferritin and depression symptoms. Inflammation could explain these discrepancies as inflammation has been associated with elevated levels of the iron biomarker serum ferritin. Therefore, inflammation could be responsible for false negatives for iron deficiency. In the study reported here, the relationship between iron status and depression was assessed in participants from three National Health and Nutrition Examination Surveys (NHANES (2005-2006, 2007-2008, and 2009-2010). Iron status was measured through serum ferritin, and depression was defined as a depression screener score ≥ 10. Individuals who had both serum ferritin data and complete depression screener data, were not pregnant, and were not on antidepressants were included in this study. The starting study population consisted of 3,452 females 18-49 years old, inflamed and non-inflamed (Inf/Non-Inf). Exclusion for inflammation (Non-Inf), defined as C-reactive protein > 2 mg/L, reduced the study population to 1,780. Further exclusions for serum ferritin outliers using the cutoff value 150 ng/mL (Non-Inf 150) lowered the study population to 1,726. This thesis also examined serum ferritin and depression in a sample with only inflamed individuals (Inf) (n = 1,672). Inflammation and serum ferritin were compared in the Inf/Non-Inf population. Iron status and depression were compared for the Non-Inf, Non-Inf 150, and Inf populations separately with the same analyses for each population. Inflammation and serum ferritin appear to be strongly correlated in the Inf/Non-Inf population. Data for the Non-Inf, Non-Inf 150, and Inf populations do not strongly suggest a relationship between iron status and depression. However, stronger associations between iron status and depression were observed in the inflamed-only population than in either non-inflamed population. This finding suggests further research could be done on iron deficiency and depression in inflamed individuals as this relationship could be different depending on an individual’s inflammation status.