THE ASSOCIATION OF THE INFLAMMATORY POTENTIAL OF DIET WITH INFLAMMATION AND DEPRESSION AMONG U.S. ADULTS: NHANES 2005-2010

Depression affects 8% of adults in America. Women are twice as likely as men to experience depression. The economic burden in the U.S. is $83 billion in direct (e.g., pharmaceutical) and indirect costs (e.g., absenteeism from work). The etiology of depression includes non-modifiable (e.g., genetics) and modifiable risk factors (e.g., diet). Depression is concurrent with an increase in inflammatory biomarkers, such as c-reactive protein (CRP). Emerging research suggests that a pro-inflammatory diet may increase odds of experiencing depression. The Dietary Inflammatory Index (DII) assesses the inflammatory potential of diet. According to our narrative review of the current literature in Chapter 1, the association of the DII and depression is stronger among women than it is in men. While many studies have found significant associations between the DII and depression, no study to date has evaluated the mediation role of inflammation on this association. The association of the DII with various types of depression (e.g., somatic, cognitive) has not been studied. Previous research has not contrasted the association of DII and depression among pre- and post-menopausal women. The aim of this dissertation was to examine the association of the DII with different types of depression, study the mediation role of inflammation in these associations, and compare the results among pre- and post-menopausal women. For our analyses, we used the National Health and Nutrition Examination Survey. In Chapter 2, we evaluated the mediation role of CRP on the association of the DII and different types of depression. Our results suggest that a pro-inflammatory diet is significantly associated with higher odds of major depression. The mediation role of CRP on this association was significant but not biologically meaningful. In Chapter 3, we compared the association of the DII and depression among pre- and post-menopausal women. The association of a pro-inflammatory depression with higher odds of major depression was stronger among pre-menopausal women. In conclusion, CRP does not strongly mediate the association between the DII and depression. The association of DII and depression is stronger in women, especially pre-menopausal women. Future studies need to replicate these results in longitudinal studies, using various inflammatory biomarkers