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Toxoplasma Gondii and Elevated Suicide Rates


The three studies that Wikipedia presents in support of the observation that T. gondii infection is associated with higher suicide rates:

J Clin Psychiatry 2012;73(8):1069-1076


This cross-sectional, observational study compared T gondii serointensity and seropositivity in plasma from 54 adult suicide attempters (inpatients at Lund University Hospital, Lund, Sweden) and 30 adult control subjects (randomly selected from the municipal population register in Lund, Sweden) recruited between 2006 and 2010.

Data were analyzed using multivariable logistic regression to investigate the association between T gondii serointensity or seropositivity and a history of nonfatal suicidal self-directed violence; multivariable linear regression was used to explore the relationship between T gondii serointensity or seropositivity and the SUAS-S. Both regression models included sex, age, and body mass index as covariates.

Seropositivity of T gondii (adjusted odds ratio [OR] = 7.12; 95% CI, 1.66–30.6; P =.008) and serointensity of T gondii (adjusted OR = 2.01; 95% CI, 1.09–3.71; P = .03) were positively associated with a history of nonfatal suicidal self-directed violence.

Arch Gen Psychiatry. 2012;69(11):1123-1130

Register-based prospective cohort study. Women were followed up from the date of delivery, 1992 to 1995 until 2006.

Setting Denmark.

Participants A cohort of 45 788 women born in Denmark whose level of Toxoplasma -specific IgG antibodies was measured in connection with child birth between 1992 and 1995.

Results T gondii– infected mothers had a relative risk of self-directed violence of 1.53 (95% CI, 1.27-1.85) compared with noninfected mothers, and the risk seemed to increase with increasing IgG antibody level. For violent suicide attempts, the relative risk was 1.81 (95% CI, 1.13-2.84) and for suicide, 2.05 (95% CI, 0.78-5.20). A similar association was found for repetition of self-directed violence, with a relative risk of 1.54 (95% CI, 0.98-2.39).

Journal of Nervous & Mental Disease:
The strongest association was in the 60- to 74-year-old group where, after adjustment for GDP, the relationship (p = 0.007) resisted Bonferroni adjustment for multiple comparisons. In conclusion, the results suggest that a positive relationship between rates of infection with T. gondii and suicide is apparent in women of postmenopausal age. Prospective studies are necessary to further confirm this association predictively and to explore mechanisms mediating this relationship.
These three studies are referenced in Wikipedia for the statement that T. gondii seems to elevate suicide risk.  Other studies suggest increased risk of schizophrenia (which has a high suicide rate) as well.
There appears to be about double the rate of suicide in patients with antibodies to T. gondii.  This suggests that this neurotrophic parasite may affect a person’s thinking.  This is especially troubling in light of the discovery that T. gondii infection causes mice and rats to become attracted to cat urine instead of fearful of it.
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