Relationship between Toxoplasma gondii infection and bipolar disorder in a French sample

Background: Prenatal exposure to viruses or parasites with tropism for the central nervous system is one of the risk factors for psychotic disorders. However, the relationship between past exposure to Toxoplasma gondii (T. gondii) and incidence of bipolar disorders (BD) is poorly documented across populations.

Methods: We explored the potential association between T. gondii exposure and BD in France, a country of high prevalence of Toxoplasmosis, comparing the prevalence of serological markers (IgG/IgM class antibodies) for T. gondii infection in 110 BD patients and 106 healthy controls all living in France. In a subgroup of 42 patients and 42 controls we also evaluated the levels of interleukin 6 (IL-6) transcripts, an adjunct marker of inflammation.

Results: We found that the sero-positive group for IgG antibodies to T. gondii had a 2.7 fold odds of having BD as compared to the sero-negative group (OR=2.17 CI 95%=1.09-4.36, p=0.028). Despite the fact that BD patients had significantly higher levels of IL-6 than the non-patient controls, no notable association between T. gondii status and IL-6 transcript levels was found. We did not find any clinical or demographic correlates of Toxoplasma exposure in the study population.

Limitations: Our results are to be interpreted with caution because of our small sample size.

Results: We confirm the association between seropositive status to T. gondii and bipolar disorders reported in other populations and extend it to French patients. Our data strengthen the importance of early detection of T. gondii infected patients in order to propose specific and adequate treatments.