Inflammation, infection and depression: an evolutionary perspective.

The evolutionary basis for clinical depression is not well understood. A growing body of literature that is not based on evolutionary logic links inflammation to depression. Integration of these findings with an evolutionary framework for depression, however, needs to address the reasons why the body's inflammatory response would be regulated so poorly that it would result in incapacitating depression. Pathogen induction of inflammation offers an explanation, but the extent to which the association between inflammation and depression can be attributed to general inflammation as opposed to particular effects of pro-inflammatory pathogens remains unclear. This paper reports a study of sexually transmitted pathogens, which addresses this issue. Although several sexually transmitted pathogens were associated with depression according to bivariate tests, only Chlamydia trachomatis and Trichomonas vaginalis were significantly associated with depression by a multivariate analysis that accounted for correlations among the pathogens. This finding is consistent with the hypothesis that infection may contribute to depression through induction of tryptophan restriction, and a consequent depletion of serotonin. It reinforces the idea that some depression may be caused by specific pathogens in specific evolutionary arms races with their human host.

Sexually Transmitted Pathogens, Depression, and Other Manifestations Associated with Premenstrual Syndrome.

This study investigated whether sexually transmitted infections and lifestyle variables are associated with premenstrual syndrome (PMS) as well as particular manifestations commonly associated with PMS. Data were gathered from medical records of 500 regularly cycling women. The following infectious agents were investigated: human papillomavirus, Chlamydia trachomatis, Neisseria gonorrheae, Gardnerella vaginalis, Candida albicans, and Trichomonas vaginalis. Bivariate tests and multivariate logistic regressions were used to evaluate whether these pathogens were associated with headache, pain, nausea, and depression. Chlamydia trachomatis was significantly associated with premenstrual syndrome (PMS) and two common manifestations of PMS: depression and pain. Trichomonas vaginalis was significantly correlated with headache and Gardnerella vaginalis with nausea. None of the illness manifestations was significantly associated with the tested lifestyle variables: dietary calcium supplementation, alcohol and drug use, exercise, and smoking. These associations provide a basis for assessment of infectious causation of PMS and several manifestations of illness that are commonly associated with PMS.