4. DISCUSSION
In this case-control study, we used serological and molecular techniques to elucidate a possible connection between T. gondii and schizophrenia patients compared to healthy people. To the best of our knowledge, this is the first case-control study conducted in schizophrenia and healthy individuals with the diagnosis of T. gondii by serological and also molecular methods. Overall, T. gondii positivity was found more common in patients with schizophrenia (53.8%), compared to healthy individuals (27.5%) by ELISA in this study (p < 0.001).
Conventional diagnostic approaches for T. gondii infection include microscopical, cultural, serological, and radiological methods. Because of the fact that natural scantness of conventional diagnostic techniques, PCR may be adopted to diagnose T. gondiiinfection.13 As far as we know, there is only one study14 that has limitations such as the lack of a healthy control group and targeting the SAG1 and B1 regions in the molecular diagnosis of T. gondii , although it is approximately similar in general concept to our study. Despite its limitations in this retrospective study, the authors highlighted that the prominence to use serological and molecular techniques for correct identification ofT. gondii in schizophrenia patients.14
In recent years there has been a burgeoning concern about the influence of latent T. gondii infection on mental disorders, especially schizophrenia. The nature of this connection remains unclear, although it is conceivable that they manifest causality.15 To date, numerous studies have been carried out showing the relationship between T. gondii and schizophrenia.16–19Likewise, these studies and also our study, a meta-analysis reveals a general significant relation having with T. gondii latent infection and schizophrenia. Also, this well-designed and highly scientific paper saying that the latent T. gondii acts an impact on human behavior as well.20 After two years of this meta-analysis, a case-control study has been published to determine the association between schizophrenia and T. gondii conducted with 99 schizophrenia patients and 152 healthy blood donors. Although only serological methods were used in this study and using only this analysis has some limitations, the authors reported a positive relationship between T. gondii and schizophrenia.21
In contrast to various publications that declared a significant correlation between T. gondii and schizophrenia, some studies unable to show a significant relationship.22–24Nevertheless, it should not be underestimated that the quality and quantity of studies showing the percentages of T. gondii , which has only approximately 30% positivity in a healthy population worldwide25, was found to be elevated especially in patients with schizophrenia. In this manner, it is clear that further research is still warranted.
Suicide is a crucial emerging health problem, commonly seen in people with mental disorders, and previous suicide attempts or even suicide ideation are the best indicators of possible suicide risk.26 In 2019, a meta-analysis with the aim to determine if T. gondii is linked with suicide attempt was published.12 In this meta-analysis, 14 studies about suicide attempts were included and the authors have calculated a statistically highly significant correlation for T. gondii IgG antibodies with suicide attempters (OR = 1.39; 95% CI 1.10–1.76, p = 0006). Moreover, the authors reported that latent T. gondiiinfection may play a significant role in the risk of suicide attempts and potential agents should be evaluated further.12
Besides the contribution of our study with preliminary results ofT. gondii and suicidal attempt history relation in patients with schizophrenia, there are two major limitations in this study that could be addressed in future further research. First, we enrolled a relatively small sample size (in 117 patients with schizophrenia), which would bias the results of our overall and subdivided schizophrenia group analyses toward the null hypothesis. Second, we were unable to evaluate the first-episode psychosis in stages of schizophrenia in the case group. As previously noticed27, if patients with the first-episode psychosis of schizophrenia were possible to include in our study, these outcomes would provide an idea or even insight into howT. gondii behaves during the development of this surreptitious disease.