Decreased level of psychobiological factor novelty seeking and lower intelligence in men latently infected with the protozoan parasite Toxoplasma gondii Dopamine, a missing link between schizophrenia and toxoplasmosis?
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Abstract
Toxoplasma gondii, a parasitic protozoan, infects about 30-60% of people worldwide.
The latent toxoplasmosis, i.e. life-long presence of cysts in the brain and muscular
tissues, has no effect on human health. However, infected subjects score worse in
psychomotor performance tests and have different personality profiles than Toxoplasma-negative
subjects. The mechanism of this effect is unknown; however, it is supposed that presence
of parasites' cysts in the brain induces an increase of the concentration of dopamine.
Here we search for the existence of differences in personality profile between Toxoplasma-positive
and Toxoplasma-negative subjects by testing 857 military conscripts using a modern
psychobiological questionnaire, namely with Cloninger's Temperament and Character
Inventory (TCI). ANCOVA showed that Toxoplasma-positive subjects had lower Novelty
seeking (NS) scores (P=0.035) and lower scores for three of its four subscales, namely
Impulsiveness (P=0.049), Extravagance (P=0.056) and Disorderliness (P=0.006) than
the Toxoplasma-negative subjects. Differences between Toxoplasma-negative and positive
subjects in NS was inversely correlated with duration of toxoplasmosis estimated on
the basis of concentration anti-Toxoplasma antibodies (P=0.031). Unexpectedly, the
infected subjects had also lower IQ (P(2)=0.003) and lower probability of achieving
a higher education (P(2)<0.0000). Decrease of NS suggests that the increase of dopamine
in brain of infected subjects can represent a missing link between toxoplasmosis and
schizophrenia.