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Table 1 Studies reporting on toxoplasmosis and human personality trait variation

From: Failure to replicate associations between Toxoplasma gondii or hepatitis C virus infection and personality traits

Reference Sample Scale Results and conclusions
Flegr and Hrdy 1994 University staff and biology students (195 men and 143 women) Cattell’s 16-factor questionnaire Significant correlation between chronic toxoplasmosis and two personality factors: G—low superego strength (P = 0.003)—and L—protension (suspecting, jealous, and dogmatic) (P = 0.002)
Flegr et al. 1996 First sample: 224 men and 170 women (university staff and students)
Second sample: 190 men diagnosed with Toxo in various Prague hospitals
Cattell’s 16-factor questionnaire For men, factor G (superego strength), L (protension), O (guilt proneness), and Q2 (self-sufficiency) were positively associated with infection. For women, the associated factors were A (Affectothymia), L (protension), O (guilt proneness), and Q2 (self-sufficiency) in the first sample. Second sample: positive correlation between the duration of latent toxoplasmosis and intensity of superego strength decrease (P < 0.02)
Flegr et al. 1998 University students and faculty members (243 men and 343 women) Cattell’s 16-factor questionnaire Contact with cats and history of consumption of raw meat associated with specific personality traits (high “ergic” tension: tense, frustrated, high energy, and time driven). Other traits associated with anti-Toxo cellular immunity
Flegr and Havlicek 1999 Pregnant women (N = 191; 18–39 years old) Cattell’s 16-personality factor (16PF) Subjects with latent infection (asymptomatic) showed higher intelligence, lower guilt proneness, and higher “ergic” tension (tense, high energy, impatient, driven, frustrated, over wrought, time driven)
Flegr et al. 2000 Women diagnosed with acute toxoplasmosis (N = 230) Cattell’s 16 PF questionnaire mailed to participants Significant correlation between duration of toxoplasmosis and scores on factors G (high superego strength) and Q3 (high strength of self-sentiment)
Flegr et al. 2003 Male military conscripts (N = 857) Cloninger’s Temperament and Character Inventory (TCI) Toxoplasma-seropositive participants had lower novelty seeking scores
Lindova et al. 2006 University students (N = 263) Double-blind behavioral experiments Significant interaction between gender and Toxoplasma gondii seropositivity for composite behavioral variables (self-control and clothes tidiness, analogous to the 16PF factors G—conscientiousness—and Q3—self-control)
Novotna et al. 2005 Military personnel (N = 533) tested for cytomegalovirus and toxoplasma gondii exposure Cloninger’s Temperament and Character Inventory (TCI) personality test Toxoplasma and cytomegalovirus exposure were associated with a reduction in novelty seeking
Hashim et al. 2011 Pregnant women (N = 86, toxoplasma antibody seropositive, N = 68, toxoplasma seronegative) A semi- structured interview for assessment of personality and behavior changes Rates of pseudo-psychopathic and limbic personality epilepsy syndrome were significantly higher among toxoplasma seropositive pregnant women
Khademvata et al. 2013 University students (N = 237; 111 men and 126 women) Cattell’s 16 personality factor questionnaire Women with latent toxoplasmosis had a significantly different personality profile from women without toxoplasmosis, namely higher O (apprehension), N (privateness) and Q4 (tension) scores, and lower Q1 (openness to change) scores. Infected men had significantly higher L (vigilance, mistrust) scores compared to non-infected men. Factors E (dominance) and Q1 (openness to change) tended to be higher in infected men than non-infected men, but the difference was not quite statistically significant
Cook et al. 2015 Participants (N = 1000) were recruited as healthy controls as part of a case-control study of schizophrenia at the University of Munich, Germany Participants were assessed by the Questionnaire for Measuring Factors of Aggression, a German version of the Buss-Durkee Hostility Questionnaire. Impulsive sensation-seeking was measured using the disinhibition subscale of the Sensation Seeking Scale-V In a large community sample of psychiatrically healthy volunteers, latent infection with T. gondii was significantly associated with multiple measures of trait aggression and impulsivity. These differences were largely specific to combinations of age and sex. In particular, latent toxoplasmosis was associated with higher reactive aggression scores among women, with an opposite pattern among men. Impulsive sensation-seeking was also associated with T. gondii status among males under age 60