Background: Psychiatric disorders negatively affect individuals' quality of life. It is believed that latent toxoplasmosis is associated with mental illnesses and personality changes due to its neurotropic nature. Experimental evidence in rodent models and controlled behavioral studies in people that show elevated seropositivity of anti-toxoplasma antibodies in individuals with mental problems all strongly support this theory. In this study, we tried to shed light on the role of toxoplasmosis as a risk factor for some psychiatric disorders, aiming to treat those patients and improve their life performance.

Methods: A case control study was performed in the psychiatry outpatient clinic, Zagazig University Hospital and Medical Parasitology Department, Faculty of Medicine, Sharkia Governorate, Egypt. This study included 152 subjects (76 patients with major psychiatric disorders and 76 healthy control subjects). The diagnosis of psychiatric disorders was according to the DSM-5 criteria for major psychiatric disorders. ELISA was used to test patients for anti-T. gondii IgG seropositivity.

Results: According to our findings, psychiatric patients had a greater seroprevalence of Toxoplasma IgG (64.5%; 49/76) than the control group (13.2%; 10/76) (p<0.001). Also, patients with major depressive disorders (MDD) had the highest prevalence of latent T. gondii infection, followed by patients suffering from schizophrenia and bipolar.

Conclusions: Patients with some psychiatric disorders showed higher seropositivity of anti-Toxoplasma IgG compared with the control group. This was evident in those with MDD. Understanding the risk factors for Toxoplasma infection may be the first step in developing future preventative measures for patients with mental illness.