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Research on infectious agents as a possible cause of schizophrenia has become prominent in the past decade. Toxoplasma gondii has emerged as a prime candidate for a variety of reasons; (i) many studies have reported that individuals with schizophrenia, compared to controls, have a higher prevalence of antibodies to T. gondii, (ii) some individuals with adult toxoplasmosis develop psychotic symptoms similar to those of schizophrenia, (iii) epidemiologically, there are many similarities between toxoplasmosis and schizophrenia, (iv) antipsychotic drugs known to be effective in schizophrenia also inhibit some parasites, including T. gondii, (v) Toxoplasma has been shown to induce elevated levels of dopamine in experimentally infected animals (elevated dopamine is commonly seen in individuals with schizophrenia) and (vi) studies have shown that individuals with schizophrenia, compared to controls, have had greater exposure to cats in childhood. A number of questions remain concerning a role for Toxoplasma in the aetiology of schizophrenia, including the roles of strain variation, the timing and source of infection, and the role of host genes in determining disease susceptibility. The establishment of a firm association between Toxoplasma and the aetiology of schizophrenia and related disorders would represent a major breakthrough in the understanding of these disorders and would lead to novel methods for their treatment and prevention.