Studies about the association of
T. gondii infection and depression have shown conflicting results [
9,
11,
12]. In addition, the association of
T. gondii infection and prenatal depression has been poorly studied in particular. Therefore, the present study aimed to determine whether
T. gondii infection is associated with depression in a sample of pregnant women in Durango City, Mexico. Results of tests for detection of
T. gondii performed in the present study included qualitative and quantitative IgG and IgM assays. Our results do not point towards an increased rate of depression in pregnant women infected with
T. gondii compared to matched control patients attended in the same hospital. We are aware of only one study on the link of
T. gondii infection and depression in pregnancy. In such study, 414 women at 16–25 weeks of gestation in the USA were examined, and researchers found that higher
T. gondii IgG antibody titers were associated with prenatal depression [
13]. Authors hypothesized that immune escape of
T. gondii may occur due to immune changes in pregnancy, and this could cause depression through activation of indoleamine 2, 3-dehydroxylase resulting in serotonin decrease [
13]. It is not clear why the association of infection and depression was found in pregnant women in the USA but not in pregnant women in the current study. Comparison of both studies was based on IgG seropositivity; however, IgM seropositivity was not compared because this marker for acute or recent infection was not determined in the American study. It is possible that differences in the characteristics of pregnant women among the studies may explain the differences in the association. In the U.S. study, researchers examined women at 16–25 weeks of pregnancy whereas we examined women at 2–9 months of pregnancy. Stratification by month of pregnancy groups (2–5 months, and >5 months) did not show an association of infection and prenatal depression in the current study. While our study did not find any association of infection with
T. gondii and depression in pregnant women several studies have demonstrated a link between
T. gondii infection and depression.
T. gondii seropositivity correlated with the Center for Epidemiologic Studies Depression score, Profile for Mood States-depression, and total mood disturbance score in a study of women veterans in the USA [
17]. The age of women in the latter study was higher than in our study. Experimental evidence exists that reactivation of chronic
T. gondii infection in mice by an immunosuppressive regimen caused depression-like behaviors, specifically, reduced sucrose preference, and increased immobility in the forced-swim test [
18]. Researchers of the latter study also observed an enhanced tryptophan catabolic shunt and serotonin turnover that may be involved in the development of the depressive-like behaviors [
18]. Reactivation of latent infection in humans is often observed in immunocompromised patients leading to life-threatening toxoplasmic encephalitis; it is therefore difficult to study an association with depression.
False positive results have been reported in anti-
T. gondii IgM antibody tests [
19]. Therefore, to increase the specificity of IgM seropositivity, we used two methods to test for anti-
T. gondii IgM antibodies (EIA and ELFA). No acute cases of
T. gondii infection were found, and therefore, treatment against
T. gondii in the pregnant women studied was not needed.
Our study has limitations. First, we investigated the association of infection with T. gondii and depression in a relatively small cohort of pregnant women attending a public hospital. Therefore, our results cannot be extrapolated to pregnant women with different social status, i.e., those attended in private hospitals or other public hospitals. The great majority of women attended in the participating hospital had a low socioeconomic status.