Toxoplasma gondii, trait aggression and impulsiveness in healthy adults (Cook et al. 2015)
Impulsivity and aggression have been described as endophenotypes for suicidal behaviour (Mann et al. 2009, Gould et al. 2017). For inclusion in the control group (N = 1000), individuals needed to meet two criteria: they HAD TO have no history of suicide attempts and had to show no evidence of DSM-IV Axis I or Axis II disorders when evaluated using the Structured Clinical Interview. Blood samples were drawn for all participants and plasma antibodies against T. gondii and two other latent neurotropic pathogens (HSV-1 and CMV) measured with ELISA. Participants were assessed with a German version of the Buss-Durkee Hostility and with the Disinhibition subscale of the Sensation Seeking Scale-V for measuring impulsive sensation-seeking.
Our study revealed a gender-specific relationship be- tween T. gondii infection and personality traits of aggression and impulsivity (Cook et al. 2015). Female subjects who tested positive for T. gondii IgG antibodies demonstrated significantly elevated trait reactive aggression scores (p <0.01), while male subjects showed no such correlation. Additionally, among males (age 60 or below), T. gondii seropositivity correlated with higher impulsive sensation-seeking behaviour. The study also investigated potential associations with HSV-1 and CMV, but no statistically significant relationships were observed for either pathogen (Cook et al. 2015).
The gender differences were consistent with the pio- neering initial studies of Flegr and his group (described in Flegr 2025 in this issue). However, our study’s unique feature is the exclusion of psychopathology, including of personality disorders, using the Structural Clinical Interview for DSM-IV (SCID). This minimised the possibility of a link between T. gondii with impulsivity/aggression via the previously documented associations between T. gondii and psychopathology (described in more detail in Postolache et al. 2021), and between psychopathology and impulsivity /aggression.
Publication Date: 2025-09-05