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

Introduction: Chlamydia trachomatis is an important indicator of overall health and plays a vital role in various health conditions. In 2018, C. trachomatis 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%). C. trachomatis 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. Methods: 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 C. trachomatis in the previous year was predictive of depression. Models were adjusted for known confounders, including age, gender, race/ethnicity, poverty, and education. Results: For C. trachomatisra, the unadjusted Odds Ratio (OR) for C. trachomatis to no C. trachomatis 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 C. trachomatis but reported low CRP after adjusting for demographic and health variables. Conclusions: 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 C. trachomatis and high CRP leading to worse outcomes in individuals with depression than C. trachomatis infection alone. This finding indicates the need to conduct mental health screening among individuals with Sexually Transmitted Infections (STIs) or other infectious diseases.