T. gondii infection linked to bipolar I disorder risk
MedWire News: Infection with Toxoplasma gondii is associated with an increased risk for bipolar I disorder, results from a US study suggest.
Previous studies have indicated that the prevalence of T. gondii seropositivity is 2.7-times higher in schizophrenia patients than the general population, explain Brad Pearce (Emory University, Atlanta, Georgia) and colleagues in Biological Psychiatry.
However, they add that "the relationship of T. gondii infection and mood disorders is less clear."
To investigate further, the team studied data on 7440 respondents, aged 15-39 years, who participated in the Third National Health and Nutrition Examination Survey between 1988 and 1994.
All of the participants were assessed for mood disorders, including severe major depression, major depression, dysthymia with and without a history of major depression, bipolar I disorder, and bipolar II disorder, using DSM-III criteria.
Blood samples collected from the participants revealed that 1211 tested positive for immunoglobulin G antibodies to T. gondii.
After adjustment for factors such as age, ethnicity, gender, poverty level, education level, smoking, foreign birth, and C-reactive protein levels, the researchers found that respondents with a history of severe major depression, major depression, or dysthymia were no more likely to be seropositive for T. gondii than respondents without mood disorders.
However, patients with bipolar I disorder who had experienced both manic and depressive episodes (n=41) were significantly more likely to be seropositive for T. gondii than other respondents, at an adjusted odds ratio of 2.4.
The researchers note that the association between T. gondii seroprevalence and bipolar II disorder could not be assessed because of limited data.
Pearce and team conclude: "Given that most studies have found a connection between T. gondii and schizophrenia, our finding that T. gondii is not associated with unipolar depression but might be associated with a subtype of bipolar disorder is indirect evidence that bipolar disorder and schizophrenia might share at least some etiological pathways."
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By Mark Cowen