Toxoplasmosis infection and schizophrenia: Elevated IgM reactivity index as a predictor of symptom worsening in chronic schizophrenia

Abstract

The association between schizophrenia and toxoplasmosis has been studied for decades; however, most studies have small sample sizes, and few have investigated the relationship between toxoplasmosis and schizophrenia symptoms. This study aimed to compare the prevalence of toxoplasmosis seropositivity between schizophrenia patients and healthy controls in a large Brazilian sample and to investigate the association between IgM and IgG reactivity index (RI) and the severity of schizophrenia symptoms. A multicenter, cross-sectional study assessed Positive and Negative Symptoms Scale from patients, seropositivity to toxoplasmosis as well as serointensity (RI) of IgM and IgG from blood samples of 705 subjects: 313 healthy controls and 392 schizophrenia patients (313 chronic patients and 76 first episode of psychosis). The prevalence of seropositivity to toxoplasmosis was higher in schizophrenia than in controls (OR of 1.52, 95 % CI 1.11–2.07, p = .008), especially in those in FEP (OR = 1.99, 95 % CI 1.02–2.97, p = .042). Also, IgM RI was positively associated with the PANSS total (p = .012, R² = 0.17), positive (p = .017, R² = 0.17), and general scores (p = .018, R² = 0.14) in chronic patients. Toxoplasmosis is associated with schizophrenia, especially in patients in their first psychotic episode; moreover, RI of IgM was positively associated with the severity of the psychosis in chronic patients, which suggests that new infection may worsen symptomatology.