Authors: Emy Beaumont, Jacques Brodeur, Frédéric Thomas, Antoine M. Dujon, Sonia Lupien

Source: Psychoneuroendocrinology (Feb 2024)

Abstract

Background: Schizophrenia is a mental illness that affects approximately 24 million people worldwide. Vulnerability to schizophrenia has been linked by some epidemiologic studies to Toxoplasma gondii (TG), an intracellular protozoan parasite that can form permanent cysts in the brain. Knowing that stress can increase the permeability of the blood-brain barrier, we hypothesized that stress could facilitate brain infection by TG, thus promoting the development of schizophrenia symptoms. The objective of this study was to test if different types of stress: acute stress (salivary cortisol), chronic stress (hair cortisol), or childhood adversity (Childhood Experiences of Violence Questionnaire), modulate the link between TG (TG antibodies in serum) and schizophrenia.

Method: Data and biospecimens (saliva, hair and serum) from 226 schizophrenic patients and 129 controls from the Signature Bank of the Centre de recherche de l’Institut Universitaire en Santé Mentale de Montréal were analysed. Hypothesis was tested using logistic regressions. Sex and age were included as covariates.

Results: Interaction effects revealed that the relation between TG seropositivity and the risk of developing schizophrenia was modulated by levels of hair cortisol (chronic stress; OR = 3.97, CI₉₅ = 1.01- 15.71, p=.049). However, salivary cortisol (acute stress; OR = 1.72, CI₉₅ = 0.60-4.95, p=.315) and childhood adversity (OR = 1.01, CI₉₅ = 0.85-1.19, p=.931) did not increase the risk of schizophrenia in TG infected patients.

Conclusion: These results provide a step towards a better understanding of the role of stress in the association between TG and schizophrenia.