Schizophrenia and toxoplasmosis: association with catatonic symptoms

Introduction. The association between schizophrenia and toxoplasmosis has been demonstrated in a number of studies: the prevalence of schizophrenia is significantly higher in toxoplasmosis positive subjects than in those with T. gondii negative status. However, the clinical significance of this association remains poorly understood. Objectives. To identify clinical phenomena that are typical for toxoplasmosis-associated (T. gondii seropositive) schizophrenia compared to Toxoplasma-seronegative schizophrenia. Methods. A retrospective database analysis of serum samples from 105 inpatients with schizophrenia (ICD-10code: F20; including 55 male patients; mean age of 27.4 6.4 years) was carried out. The clinical examination involved a structured interview including ICD-10 and E. Bleulers criteria for schizophrenia and psychometric tests(Positive and Negative Scales of PANSS). Serum antibodies (IgG) to T. gondii were identified using ELISA. The statistical significance of any differences were evaluated using the non-parametric Mann-Whitney (U) and X2 tests. Results. The proportion of seropositive patients in the sample was 16.2%. Comparing schizophrenia patients, who were seropositive or seronegative for toxoplasmosis, there were no statistically significant differences for the mean total PANSS score, mean PANSS-P, PANSS-N or PANSS-G scores. For the majority of PANSS items, differences were also statistically insignificant, except for G5 and G6mannerism and posturing. Seropositive patients had a higher score for this item than seronegative patients: 3.5 versus 2.1 points (U=389.5; р=0.001). Depression, on the contrary,was less pronounced in seropositive than seronegative patients: 1.4 versus 2.4 points (U=509.5; р=0.023). In addition,in seropositive patients, the frequency of symptoms such as mutism according to ICD-10 criteria for schizophrenia was significantly higher (23.5% versus 3.4%, X2=9.27, р=0.013), and the whole group of catatonic symptoms according to the E. Bleulers criteria for schizophrenia was higher (52.9% versus 28.4%, X2=3.916, p = 0.048). Conclusion. The association between a positive toxoplasmosis status in patients with schizophrenia and catatonic symptoms has been revealed for the first time and should be verified in larger studies.


INTRODUCTION
A significant association between schizophrenia and toxoplasmosis caused by the neurotropic pathogen of T.gondii has been identified in a number of clinical and epidemiological studies, the results of which are illustrated, for example, in the meta-analysis by J. Gutiérrez-Fernández et al. [1]. The latter demonstrates a statistically significant correlation between the T.gondii-positive status and schizophrenia with the odds ratio (OR) of 2.50 (95% CI=1. 40-4.47). This was significantly higher (23.5% versus 3.4%, χ 2 =9.27, р=0.013), and the whole group of catatonic symptoms according to the E. Bleuler's criteria for schizophrenia was higher (52.9% versus 28.4%, χ 2 =3.916, p = 0.048).

Conclusion.
The association between a positive toxoplasmosis status in patients with schizophrenia and catatonic symptoms has been revealed for the first time and should be verified in larger studies.

RESULTS
The proportion of seropositive patients in the sample was 16.2% (17 out of 105 cases). When comparing Toxoplasma-seropositive or seronegative schizophrenia patients, no statistically significant differences were found in parameters such as the mean total PANSS score, mean PANSS-P, PANSS-N or PANSS-G scores, although there was a general trend towards a higher mean total score for all subscales and the total PANSS score among patients who were seropositive (Table 1).  Comparing Toxoplasma-seropositive and seronegative schizophrenia patients, no statistically significant differences were found in parameters such as the mean total PANSS score, mean PANSS-P, PANSS-N or PANSS-G scores. In this respect, our data are consistent with the results obtained by F. Dickerson et al. [5] who did not reveal any differences in the total PANSS score and by D. Holub et al. [9] who also found no differences in the PANSS-N or PANSS-G scores. However, D. Holub et al. [9] and H.L. Wang et al. [10] showed a higher PANSS-P in seropositive patients, which differs from our findings.
In our study, although the total PANSS-P scores were higher in seropositive patients, the differences did not reach statistical significance. Moreover, in the study by H.L. Wang et al. [10], seropositive patients were found to have significantly lower PANSS-N scores, which was not observed in our study or by other authors [5,9]. According to the authors, these psychoses could  Some authors believe that the mechanism underlying this association may be due to the ability of T.gondii to increase dopaminergic activity [19,20] or its effects on tryptophan metabolism in the corresponding structures [21], which requires verification in further morphological and neuroimaging studies.
The discussion of the association between depressionrelated symptoms in seropositive patients is beyond the scope of this article. However, we may stipulate that this is consistent with the findings of a clinical and epidemiological study by A.B. Smulevich et al.

Funding:
The study was conducted without the sponsor's support.

Conflict of Interest:
The authors declare no conflicts of interest.
Informed Consent: All patients signed the informed consent form for participation in the study and testing of biological samples.