New findings: Depression, suicide, and Toxoplasma gondii infection

Abstract

Purpose This article provides an overview of the evidence of a potential pathophysiological relationship between depression, suicide, and the Toxoplasma gondii (T. gondii) infection. It discusses the role of inflammatory processes in depressive illness and the infection theory of psychiatric disease. It also provides guidelines for the screening, diagnosis, and treatment of depression for nurse practitioners (NPs). Data source A narrative review was conducted of the literature from PubMed, PsycINFO, and Google Scholar. References of identified articles were also reviewed. Conclusions Seropositivity of the obligate intracellular protozoan parasite, T. gondii is related to various mental health disorders including schizophrenia, suicide attempt, depression, and other neuropsychiatric diseases. Depressive symptoms have been linked to interferon‐γ (IFN‐γ) blocking T. gondii growth by inducing indoleamine‐2,3‐dioxygenase (IDO) activation and tryptophan depletion, which results in a decrease of serotonin production in the brain. Although exposure to T. gondii was considered unlikely to reactivate in immune‐competent individuals, new findings report that this reactivation may be triggered by immune imbalance. Implications for practice NPs caring for patients with psychiatric illness need to understand the potential mechanisms associated with depression and the T. gondii infection in order to provide effective screening, treatment, and disease prevention.

Neurological and Neuropsychiatric Consequences of Chronic Toxoplasma Infection

“…Unipolar Depression Based on observed tryptophan depletion, which results in a decrease of serotonin level in Toxoplasma-infected subjects and increased rates of suicides and suicide attempts (see below), it was speculated that an association between toxoplasmosis and major depression could exist [57,58]. However, a systematic review of modern literature found 10 studies searching for this association with an overall OR 1.21 (CI 95 =0.86-1.7) [15••].…”

Reconceptualizing major depressive disorder as an infectious disease

“…Infection is associated with elevated inflammatory cytokines IL-6, IL-12, TNF, and IFN-γ [32,33], similarly as observed in depressed patients. A study of 20 European countries reported a positive correlation between T. gondii prevalence rates and national suicide rates [34].…”

The association between suicide attempts and Toxoplasma gondii infection

“…5) Although it is thought to be relatively harmless in immunocompetent adults, latent toxoplasmosis has been linked to several psychiatric problems including suicide. 7) For instance, the prevalence of T. gondii seropositivity was found to be higher in schizophrenia patients. 8) Arling et al 9) reported an association of T. gondii antibody titers with suicide attempts, and Coccaro et al 10) reported about the relationship between T. gondii infection and aggression.…”