Parasitic Infection Linked to Self-Directed Violence in Recent Mothers

A new study has found that mothers with positive antibody titers to Toxoplasma gondii at delivery had a higher risk of later self-directed violence or suicide.

Researchers at Aarhus University (Aarhus, Denmark;) conducted a register-based prospective cohort study involving 45,788 women in Denmark whose level of Toxoplasma-specific IgG antibodies was measured in connection with childbirth between 1992 and 1995; the women were followed up from the date of delivery until 2006. The main outcome measures included incidence rates of self-directed violence, violent suicide attempts, and suicide in relation to T. gondii seropositivity and serointensity.

The results showed that there were 488 attempts at self-harm among the cohort, for an incidence rate of 8.20 per 10,000 person-years. T. gondii–infected mothers had a relative risk of self-directed violence of 1.53 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, and for suicide, 2.05. A similar association was found for repetition of self-directed violence, with a relative risk of 1.54. The researchers suggested that a likely mechanism by which T. gondii could provoke self-harm is through a “neuroimmune path,” particularly by proinflammatory cytokines such as interleukin-6 and tumor necrosis factor-alpha. The study was published early online on July 2, 2012, in the Archives of General Psychiatry.

“Our results are consistent with the hypothesized association between T. gondii infection and self-directed violence and, in concert with other converging evidence and better understanding of underlying mechanisms, if confirmed in future studies, may lead to new prognostic, prophylactic, and therapeutic approaches to suicide prevention,” concluded lead author Marianne Pedersen, MSc, and colleagues of the Danish national center for register-based research at Arhus.

Toxoplasma gondii is a common protozoa that if ingested can migrate to the brain, where it can remain in a cystic form in glial cells and neurons. Areas in the brain favored by the parasite include the amygdala and prefrontal cortex, regions that play prominent roles in the regulation of emotion and behavior, and that show abnormalities in patients with schizophrenia. Typical sources of infection include cat litter boxes, undercooked meat that contains parasite cysts, and unwashed vegetables.

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