Elsevier

Medical Hypotheses

Volume 73, Issue 5, November 2009, Pages 799-801
Medical Hypotheses

Psychosis may be associated with toxoplasmosis

https://doi.org/10.1016/j.mehy.2009.04.013Get rights and content

SUMMARY

Many parasites induce characteristic changes in their host. The effect of Toxoplasma gondii infection on the cerebrum and neuropsychiatric patients has been increasingly emphasized in recent years. T. gondii has a high affinity for brain tissue where tachyzoites may form tissue cysts and persist for a life long time. Some psychiatric symptoms such as schizophrenia and mental retardation may be induced by the infection of T. gondii. Furthermore, experiments demonstrated that some antipsychotics and mood stabilizers used to treat psychosis displayed the function of inhibiting T. gondii replication. Investigations from various regions in China in psychotic patients support the hypotheses that psychosis may be linked to T. gondii infection.

Introduction

Toxoplasma gondii is an intracellular parasite that infects virtually all warm-blooded vertebrates including mans. It is estimated that about 30–60% of the population in both developed and developing countries are infected with this parasite through the ingestion of food and water contaminated with cysts or oocysts [1]. In immunocompetent person who infected with T. gondii, is characterized by reproduction of tachyzoite in cells of different tissues [2] and within weeks or months, tachyzoites disappear and tissue cysts form in various tissues, mainly in brain and muscles. These cysts are believed to persist throughout the life of the immunocompetent hosts in whom psychotic manifestation may be induced. Many epidemiological studies focused on patients with CNS diseases have been carried out in recent years, and increasing evidence supports the hypothesis that T. gondii infection may be an etiological factor for the development of psychosis in some patients [3], [4].

Section snippets

Dopamine modulation and etiological implication of psychosis

Many reports indicated that T. gondii might be an etiological agent in some cases of psychosis. Huber et al. suggested that parasitosis might contribute to the increase of the dopamine level in mice brain [5]. Evidence showed that dopamine is one of the key compounds related to psychosis such as schizophrenia, and bipolar disorder in laten toxoplasmosis patients [6], [7]. Dopamine releasing in the nucleus accumbens by activating the retrohippocampal region can disrupt the fornix section of

Surveying the situation of T. gondii infection in patients with psychosis on the mainland of China

A large number of epidemiologic and clinic studies collected from 1953 to 2008 have shown that T. gondii infection may contribute to some cases of psychosis [16]. In animals, experimental infection indicated that T. gondii can alter their behavior and neurotransmitter levels [17]. In humans, however, clinic evidence appears that the acute infection with T. gondii can produce psychotic symptoms similar to those displayed in persons with schizophrenia. Recently, similar investigations on the

Conclusion

The clinical and epidemiological studies mentioned above showed that there are some positive correlation between T. gondii infection and psychosis. There are some reasons based on:

First, sero-prevalence investigation in various regions of China indicates there is a positive correlation between T. gondii infection and psychotic disease. That is confirmed the results of Mortensen and his colleagues’ found that as compared with the control subjects, the individuals with first-episode schizophrenia

Acknowledgements

This work is supported by grants from Science and Technology Key Projects of Henan Province (#200703008) and China Postdoctoral Science Foundation.

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