By 2030 major depression is predicted to be the leading cause of disease burden in the world; as such, it is critical to understand factors that contribute to the development of depression. The social signal transduction theory of depression hypothesizes that adversity and social threat upregulate pro-inflammatory biomarkers leading to depression. The current study examined whether pro-inflammatory biomarkers (interleukin-6, interleukin-8, c-reactive protein, and tumor necrosis factor alpha) mediate the association between various types of childhood maltreatment (physical abuse, sexual abuse, emotional abuse, physical neglect, emotional neglect) and adult depression symptoms in a sample of 740 adults (372 female; Mage= 51.6 years, SD = 13.6) who provided retrospective report of childhood maltreatment as part of the Midlife in the United States (MIDUS) Refresher Biomarker study. Additionally, it explored whether these relations differ for males versus females. A series of linear regression analyses were run in SPSS; separate models were run for each form of childhood maltreatment and for interleukin-6, interleukin-8, c-reactive protein, and tumor necrosis factor-alpha. The results showed that childhood maltreatment is a robust predictor of adulthood depression; however, this association did not differ between biological sexes. In addition, only interleukin-6 was shown to partially mediate the association between childhood maltreatment and adulthood depression. These findings highlight the need to explore the use of interleukin-6 to screen for depression in youth. / M.S. / By 2030 major depression is predicted to be the leading cause of disease burden in the world; as such, it is critical to understand factors that contribute to the development of depression. It has been hypothesized that adversity and social threat activate pro-inflammatory biomarkers, which are proteins that can detect inflammation in the body, leading to depression. The current study examined whether several pro-inflammatory biomarkers explain the association between several types of childhood maltreatment (physical abuse, sexual abuse, emotional abuse, physical neglect, emotional neglect) and adult depression symptoms in a sample of 740 adults (372 female; Mage= 51.6 years, SD = 13.6) who provided report of past experiences of childhood maltreatment. Additionally, it explored whether these relations differ for males versus females. The results showed that childhood maltreatment is a robust predictor of adulthood depression for males and females. Of the inflammatory biomarkers examined, only interleukin-6 was shown to partially explain the association between childhood maltreatment and adulthood depression symptoms. These findings highlight the need to explore the use of interleukin-6 to screen for depression in youth.