Background: Toxoplasma gondii (T. gondii), a protozoan parasite is well known for its neuroinvasiveness and persistent effects. This intracellular parasite leads to central nervous system congenital anomalies. Moreover, some delayed less serious neuropsychiatric squeals following T. gondii infection have been reported.
Objectives: To study the correlation between T. gondii infection and schizophrenia, family members of cases were considered as the control group in order to match the two groups in terms of socioeconomic, sanitary, housing conditions and other demographic risk factors described in the etiology of T. gondii infection.
Materials and Methods: A case-control study was performed on 152 patients with schizophrenia diagnosis living in Iran, and 152 individuals from the first relatives of each schizophrenic patient, as the control group. A questionnaire inquiring about socioeconomic status, dietary habits and clinical characteristics was filled for each individual. Blood samples were taken from subjects and evaluated for T. gondii immunoglobulin G (IgG) antibody. Sera with positive results for IgG were further tested for T. gondii immunoglobulin M (IgM) antibody.
Results: The prevalence of T. gondii antibody positive cases among patients showed differences between males and females. In the patient group, IgG was positive in 53.2% whereas, 41.4% of the control group had IgG positive (P = 0.02). Age at the time of diagnosis of schizophrenic
patients with positive T. gondii IgG and IgM was significantly lower than other cases (34.2 ± 14.3 vs. 49.2 ± 11.7; P = 0.01). Patients with family members that had positive results for IgG ELISA test had higher probability for positive IgM seropositivity.
Conclusions: Our results supported the longstanding hypothesis of correlation between T. gondii infection and schizophrenia. We also considered this infection as a possible etiological factor in the development of schizophrenia.