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According to researchers, certain mental disorders are linked to toxoplasmosis, a disease mainly transmitted by domestic animals, in particular by cats. Explanations.
It is a disease that most often goes unnoticed… 80% of affected individuals, including pregnant women, experience no symptoms. This pathology is toxoplasmosis – an infection caused by a parasite which reproduces in the intestine of cats. However, the “toxoplasma gondii“is now suspected of promoting the occurrence of certain psychiatric disorders, such as schizophrenia and bipolar disorders.
Toxoplasmosis, an infection that most often goes unnoticed
Toxoplasmosis is a disease with potentially serious consequences in pregnant women, but often goes unnoticed in the rest of the population, due to its asymptomatic nature.
The disease is usually contracted by contact with cats carrying the parasite, by cleaning their litter. It can also be contracted through the consumption of poorly cleaned foods (especially vegetables) or undercooked (raw or smoked meats and fish).
Acute infections linked to certain psychiatric disorders
Several teams of researchers have already looked into the subject, as reported by our colleagues from Parisian.
In 2013, four biologists from the University of California at Berkeley noticed that mice infected with the “toxoplasma gondii” parasite no longer feared felines. However, this surprising behavioral change persisted even after the infection disappeared.
“It is possible that Toxoplasma gondii causes a permanent change in the brain during an acute infection“, had then concluded the researchers.
Another study on the subject, this time dating from 2015, had pointed to a higher than average prevalence of toxoplasmosis “in people with schizophrenia and obsessive-compulsive disorder“.
At the same time, a survey relayed by Inserm indicated that in infected patients, the use of psychotropic drugs with an anti-toxoplasmic effect reduced “more the frequency of depressive episodes than psychotropic drugs without effect on the parasite“.
Many studies have thus linked this infection with schizophrenia or tantrums or intermittent explosive disorder (IED). Strangely, other studies had it down to our political orientations or even our potential for seduction.
Correlation is not causation
If the toxoplasmosis-mental health association seems plausible on paper (the parasite Toxoplasma gondii can survive in brain cells involved in the dopaminergic circuit, itself associated with psychiatric illnesses such as schizophrenia), no causal link could be demonstrated.
“Correlation is not causation, and that’s certainly no reason to get rid of your cats“, confided Royce Lee, professor of psychiatry and behavioral neurosciences at the University of Chicago, himself co-author of a study on toxoplasmosis and aggression. “We do not yet understand the mechanisms involved: it could be an increased inflammatory response, direct modulation of the brain by the parasite, or even reverse causation, whereby aggressive individuals tend to have more cats or eat more undercooked meat.”
It is therefore difficult to draw (too) hasty conclusions on the association toxoplasmosis and mental health, “even if this link is getting closer“, concludes Inserm.