Depressiveness and neuroticism in Bartonella seropositive and seronegative subjects – preregistered case-controls study (data)

Several recent studies have demonstrated the association of cat-related injuries with major depression and with depressiveness in the general population. It was suggested that cat-scratch disease, the infection with the bacterium <i>Bartonella</i> <i>henselae</i>, can be responsible for the observed association. However, no direct evidence for the role of the <i>Bartonella</i> infection in this association has been published until now. In this preregistered case-controls study performed on 250 healthy subjects tested earlier for the presence of anti-<i>Toxoplasma</i> IgG antibodies, we searched for the positive association between presence of anamnestic anti-<i>Bartonella</i> IgG antibodies and depressiveness measured with Beck II inventory, depression subscale of neuroticism measured with N-70 questionnaire, and self-reported health problems. We found that that <i>Bartonella</i>-seropositivity was positively correlated with Beck depression only in <i>Toxoplasma</i>-seronegative men and negatively correlated with health in <i>Toxoplasma</i>-seronegative women. <i>Bartonella</i> seropositivity expressed protective effects against <i>Toxoplasma</i> seropositivity-associated increased neuroticism in men while <i>Toxoplasma</i>-seropositivity expressed protective effects against <i>Bartonella</i> seropositivity-associated health problems in women. A comparison of the patterns of association of mental and physical health problems with <i>Bartonella</i> seropositivity and with reported cat-related injury suggests that different factor, possibly infection with different pathogen transmitted by cat related-injuries than the <i>Bartonella</i> <i>henselae</i>, is responsible for the observed association of cat related-injuries with depressiveness and major depression. The existence of complex interactions between <i>Bartonella</i> seropositivity, <i>Toxoplasma</i> seropositivity, and sex also suggest that the effect of symbionts on the host’s phenotype must by always studied in the context of other infections, and separately for men and women.