1. INTRODUCTION
Toxoplasma gondii (T. gondii ) is a neurotropic parasite affecting warm-blooded animals including humans1 and is found in more or less 30% of people.2 Felines are the final host for T. gondii , shedding in their feces up to millions of oocyst stages daily, which become contagious in nature.3 In people, the infection may be transmitted by the ingestion of water or food. In this way, the majority of T. gondii infections remain asymptomatic or maybe produce infectious mononucleosis in people who have an intact immune system. Severe toxoplasmosis may develop if T. gondii infects immunocompromised patients such as acquired immunodeficiency syndrome (AIDS).4 In parallel with the achievements after the concept of microbiota, it is thought that microorganisms may be associated with non-infectious pathological changes.
The pathophysiology of schizophrenia is tangled, and biological factors are among the leading causes.5 Thus, studies focusing to elucidate the possible agents in schizophrenia have been carried out. In many studies conducted for this purpose, T. gondii has been evaluated as the prominent agent in this relationship due to its tropism and persistence in the brain.6 Several reports are describing that T. gondii is linked to the elevated risk of mice catching by felines,7 to modulated behavioral change by influencing neurotransmitters in the human brain.8In humans, dysregulation of some neurotransmitters is significantly related to schizophrenia. T. gondii can synthesize tyrosine hydrolase and thus dopamine dysregulation may occur. Furthermore,T. gondii also modifies the level of a vast of other neurotransmitters, including glutamate, serotonin, norepinephrine, and γ-aminobutyric acid (GABA).9 The link between schizophrenia and T. gondii seems to be vigorous, as evidenced by numerous seroprevalence and neurotransmitter studies.
Worldwide, almost 800.000 people die by suicide and roughly 10 million individuals attempt suicide annually. Suicide attempts are recognized to be a complex mechanism, with psychological, social and biological perspectives involved.10 In 2009, T. gondii , a hitherto unforeseen agent, has been associated with the suicide attempt. The possible relationship between T. gondii and suicide attempts has also been shown in a current seroprevalence study. According to the author, T. gondii IgG positivity was statistically highly correlated with lower agreeableness, lower conscientiousness and higher neuroticism personality types.11 Overall, topic-related and current studies provide considerable evidence for the hypothesis that T. gondii infections maybe take a key position in the risk of the suicide attempt.12
In this case-control study, it was aimed to elucidate the relationship between T. gondii , which was detected by serological and molecular methods, and patients with schizophrenia, and the suicide attempt by comparing it with the healthy individuals.