An association between Chlamydia trachomatis infection and depression in asymptomatic patients

Prolonged immune responses to persistent infections may contribute to depression. Among sexually transmitted pathogens, Chlamydia trachomatis is uniquely associated with depression (Doyle et al. 2015). However, previous studies of this association included only female subjects and did not distinguish symptomatic from asymptomatic infection. If C. trachomatis causes depression through chronic immune responses, then the relation between infection and depression should hold for subjects without recognized symptoms of C. trachomatis infection. The present study examines whether C. trachomatis infection is associated with depression in asymptomatic male and female patients. We conducted a study using data from The University of Louisville Health Services Center electronic medical records. Depression was evaluated using PHQ-2 and PHQ-9 screening questionnaires. Patients who were tested for C. trachomatis and who took a PHQ questionnaire prior to their examination were included. Screening for asymptomatic patients included only those who underwent STD testing as part of a routine or unrelated medical examination and who were reported by the attending physician to have no current or recent STD symptoms. Among all reviewed patients (n = 809), 138 (17.1%) reported depression. Asymptomatic infected patients were significantly more likely to report depression than uninfected patients (p =.037). However, there was no significant difference in the likelihood to report severe depression between infected and uninfected patients (p =.643) and there was no significant difference in the likelihood to report depression between infected males and infected females (p =.829). Our results support previous findings of a positive association between C. trachomatis and depression in women, yet extend them by demonstrating that the relation stands for both sexes and for patients with asymptomatic infection. The results implicate C. trachomatis in mild and moderate depression, but not severe depression. Further studies are needed to demonstrate a causal connection between C. trachomatis and depression, including exploration of already proposed mechanisms.