Interactive Effect of C-Reactive Protein upon the Relationship Between Chlamydia trachomatis and Depression

<b>Introduction</b>: <i>Chlamydia trachomatis</i> is an important indicator of overall health and plays a vital role in various health conditions. In 2018, <i>C. trachomatis</i> reached the highest level ever recorded, resulting in USD 691 million in expenditures, with 1.8 million reported cases. This amount reflects a 19% increase since 2014, according to the Centers for Disease Control and Prevention. Depression has also been on the rise between 2013 (8.2%) to 2023 (13.1%). <i>C. trachomatis</i> and depression may have inflammation as a final common pathway. The purpose of this study was to explore a potential connection between Chlamydia and depression, and whether C-reactive protein (CRP) modifies this effect. <b>Methods</b>: For this study, we utilized the 2005-2016 National Health and Nutrition Examination Survey (NHANES) and US adults aged between 20 and 59 years. Depression was determined from the Patient Health Questionnaire (PHQ-9). Logistic regression models were used to determine if <i>C. trachomatis</i> in the previous year was predictive of depression. Models were adjusted for known confounders, including age, gender, race/ethnicity, poverty, and education. <b>Results</b>: For <i>C. trachomatisra</i>, the unadjusted Odds Ratio (OR) for <i>C. trachomatis</i> to no <i>C. trachomatis</i> was OR = 2.9. The adjusted OR was elevated, at OR = 6.3 among individuals who had both CT and elevated CRP, but close to 1.0 among individuals who had <i>C. trachomatis</i> but reported low CRP after adjusting for demographic and health variables. <b>Conclusions</b>: Using a nationally representative sample, our study was the first to demonstrate, across unadjusted and adjusted models, that there is a strong connection between a history of <i>C. trachomatis</i> and high CRP leading to worse outcomes in individuals with depression than <i>C. trachomatis</i> infection alone. This finding indicates the need to conduct mental health screening among individuals with Sexually Transmitted Infections (STIs) or other infectious diseases.