T. gondii link to schizophrenia supported

By Mark Cowen

Study results support an associated between maternal infection with Toxoplasma gondii and an increased risk for schizophrenia in offspring.

The researchers found that individuals born to women with evidence of T. gondii infection or cytomegalovirus (CMV) were more than twice as likely to develop schizophrenia as those born to uninfected women.

"This is the third study showing an association between high levels of maternal antibodies directed at T. gondii and the later development of schizophrenia in the offspring," comment Åsa Blomström (Karolinska Institutet, Stockholm, Sweden) and team.

"Thus, the balance of evidence favors a role of T. gondii in the etiology of schizophrenia."

The findings come from a study of 198 individuals with schizophrenia or other non-affective psychoses who were born between 1975 and 1985 and 524 age-, gender, and birth hospital-matched mentally healthy individuals (controls).

Archived neonatal dried blood samples from the participants were assessed for levels of immunoglobulin (Ig)G against T. gondii, cytomegalovirus (CMV), and herpes simplex virus type 1 (HSV-1) and 2 (HSV-2) using immunoassays.

Analysis revealed that levels of IgG against T. gondii above the 75th percentile of those in the general population, indicating maternal infection, were associated with a 2.1-fold increased risk for schizophrenia.

Similarly, levels of IgG against CMV above the 25th percentile of those in the general population were associated with a 2.2-fold increased risk for schizophrenia.

Furthermore, the risk for schizophrenia increased with higher levels of antibodies to T. gondii and CMV, the researchers note.

By contrast, there was no significant association between IgG levels against HSV-1 and HSV-2 and an increased risk for schizophrenia, or between any of the infectious agents assessed and risk for other types of non-affective psychosis.

Blomström and team conclude: "This study supports findings of maternal exposure to T. gondii and schizophrenia risk in offspring, and extends the risk to also include maternal exposure to CMV.

"Future studies should confirm the association with CMV exposure and identify mechanisms underlying these associations."

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