The balance of evidence “suggests” some kind of association between T. gondii, a common parasite found in cats, and schizophrenia, bipolar, obsessive-compulsive disorder and addiction, according to a meta-analysis in Acta Psychiatrica Scandinavica. However, the relationship does not seem to be as strong as has been argued by other researchers such as E. Fuller Torrey, the authors wrote.
A team of researchers in The Netherlands reviewed 50 studies looking at the potential association of T. gondii to psychiatric disorders. There did seem to be significant associations especially with schizophrenia, they reported, but there was also significant publication bias, including many unpublished studies.
“After controlling for evidence of publication bias, the association of Toxoplasma gondii infection with schizophrenia seems to be smaller than previously estimated,” the authors wrote. Furthermore, other moderating factors, such as the level of existing infection in a general population, “accounted for 56% of the observed variance in study effects.”
“We hypothesize that there is a limited population at risk, by which T. gondii infection plays a role,” wrote the researchers. They also noted that being diagnosed with, developing, or being treated for schizophrenia seemed to be associated with a recurrence of a latent infection. “These findings suggest that T. gondii infection is associated with several psychiatric disorders and that in schizophrenia reactivation of latent T. gondii infection may occur,” they wrote.
The researchers argued that “uncertainty concerning the support for a causal etiology still remains.”
Sutterland, A. L., G. Fond, A. Kuin, M. W. J. Koeter, R. Lutter, T. van Gool, R. Yolken, A. Szoke, M. Leboyer, and L. de Haan. “Beyond the Association. Toxoplasma Gondii in Schizophrenia, Bipolar Disorder, and Addiction: Systematic Review and Meta-Analysis.” Acta Psychiatrica Scandinavica, April 1, 2015, n/a – n/a. doi:10.1111/acps.12423. (Abstract)