Results from a French study support an association between Toxoplasma gondii infection and bipolar disorder (BD).
Ryad Tamouza (University Paris Diderot) and team found that patients with BD were more than twice as likely to test positive for T. gondii antibodies as mentally healthy individuals.
The magnitude of the association was similar to that previously observed in patients with schizophrenia, note the researchers in the Journal of Affective Disorders.
"If confirmed, the herein reported association between BD and T. gondii will have major impact on diagnostic and treatment of bipolar patients," they comment.
The team studied 110 BD patients and 106 mentally healthy controls who supplied blood samples for assessment of T. gondii antibodies and interleukin 6 (IL-6) transcript levels - a marker of inflammation.
There were no significant differences between the groups regarding gender distribution, ethnicity, education level, working status, season of birth, rural/urban dwelling, and contact with a cat during childhood.
Overall, 76.9% of BD patients tested positive for immunoglobulin G antibodies to T. gondii compared with 48.2% of controls.
The high prevalence of T. gondii antibodies in both the BD patients and controls reflects high infection rates reported in the general population of France - a country with an increased consumption of high-risk foods, such as uncooked meat and unpasteurized cheese.
After accounting for age, the researchers found that BD patients were significantly more likely to test positive for T. gondii antibodies than controls, at an odds ratio (OR) of 2.17.
"This OR is close to the values observed for schizophrenia patients (OR=2.70-2.73)," writes the team.
There was no significant association between T. gondii status and IL-6 transcript levels, however.
Tamouza et al conclude: "Although our results are to be interpreted with caution because of the small sample size, they do raise the possibilities of developing therapeutic strategies that take into account the immuno-inflammatory and serological status of BD patients in the future."
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