Assessing the Relationship Between Exposure to Toxoplasma gondii and the Development of Schizophrenia

Abstract

Background: Multiple studies have proposed a relationship between infection with the parasite Toxoplasma gondii (T. gondii) and the onset of schizophrenia. Humans are infected with this parasite via exposure to cat feces, ingesting contaminated food and water or through transplacental transmission. It is estimated that roughly 11% of the world population is infected with Toxoplasma1. Schizophrenia is a psychiatric disorder, and affects approximately 1.1% of the population over 18 years old worldwide2. We hypothesize that individuals infected with Toxoplasma may be at an increased risk of developing schizophrenia. Objective/Purpose: To elucidate the relationship between exposure to Toxoplasma gondii and the development of schizophrenia. Methods: Journals such as: Nature, Annals of General Psychiatry, The Journal of Psychoses and Related Disorders, Acta Psychiatric Scandinavia, Infectious Diseases Society of America, Schizophrenia Research and The U.S. National Library of Medicine National Institutes of Health were used to collect information regarding exposure to T. gondii and the development of schizophrenia. Limits of our search involved language filters. Only English journals that contained our keywords: infection, schizophrenia and Toxoplasma gondii, were selected. Results: 9 relevant studies were found. The type of reviews and study designs varied, including 2 meta-analysis, 4 case controls, 1 cross sectional analysis, 1 prospective cohort study and 1 narrative review. 8 of the 9 studies reported statistically significant data showing increased levels T. gondii in schizophrenic patients. P-values, chi-square, and odds ratio measures of association were used to determine statistical significance. Conclusion: There is a growing body of data to indicate that T. gondii infection may be associated with the development of schizophrenia. Further study is needed to determine a concrete association between T. gondii infection and schizophrenia, as well as to elucidate the mechanism relating infection with T. gondii to the development of schizophrenia.