Is there a relation between the manipulative activity of Toxoplasma and personalized medicine?
Flegr, J.
Expert Review of Anti-Infective Therapy 2018; 16: 1-3
Puppet master: possible influence of the parasite Toxoplasma gondii on managers and employees
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The article reviews recent literature on the effects of host manipulation by the parasite Toxoplasma gondii (prevalent in about a third of the world's population) on perception, cognition, and behavior of humans, and on the changes in their physical appearance and personality characteristics. I argue that the mind-affecting parasite paradigm offers many research opportunities for management sciences, especially for organizational psychology and neuroscience. The article summarizes the parasite's physiological mechanisms of affecting the host; highlights important behavioral effects of the infection in humans; and speculates on the possible impacts on skills and careers of employees and managers, organizational dynamics, intercultural management, and gender work roles. The conclusion shows limitations of the presented speculations and possible directions for future research on Toxoplasma's effect on organizational dynamics.
Does Toxoplasma infection increase sexual masochism and submissiveness? Yes and no
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Flegr, J.
Communicative & Integrative Biology 2017; http://dx.doi.org/10.1080/19420889.2017.1303590
Flegr, J.
Communicative & Integrative Biology 2017; http://dx.doi.org/10.1080/19420889.2017.1303590
Click for abstract
The parasite
Toxoplasma
needs to get from its intermediate hosts, e.g. rodents, to its definitive
hosts, cats, by predation. To increase the probability of this occurrence,
Toxoplasma
m
anipulates
the behavior of its hosts, for example,
by the demethylation of promoters of certain genes in
the host’s amygdala. After this modification, the stimuli that normally activate fear
-
related
circuits, e.g. the smell of a cat,
or smell of leopards in chimpanzee,
start to additionally co
-
activate se
xual arousal
-
related circuits in the infected rodents. In humans, the increased
attraction to masochistic sexual practices was recently observed in a study performed on
36,564 subjects. Here I show that lower rather than higher attraction to sexual masochi
sm and
submissiveness among infected subjects is detected if simple univariate tests instead of
multivariate tests are applied to the same data. I show and discuss that
when analyzing
multiple effects of complex stimuli on complex biological systems we n
ee
d to use multivariate
techniques and very large data sets. We must also accept the fact that any single factor usually
explains only a small fraction of variability in the focal variable
Toxoplasma gondii infection: Relationship with aggression in psychiatric subjects
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Coccaro, E. F., Lee, R., Groer, M. W., Can, A., Coussons-Read, M., Postolache, T. T.,
Journal of Clinical Psychiatry 2016; 77: 334-341.
Coccaro, E. F., Lee, R., Groer, M. W., Can, A., Coussons-Read, M., Postolache, T. T.,
Journal of Clinical Psychiatry 2016; 77: 334-341.
Click for abstract
Objective: Toxoplasma gondii (T. gondii), a protozoan parasite that persists in host tissues, including brain, has been associated with several psychiatric disorders and with suicidal behavior. We sought to test the hypothesis that latent T. gondii infection, as manifest by circulating immunoglobulin G (IgG) antibodies to T. gondii, is associated with both categorical and dimensional measures of aggression.
Method: IgG antibodies to T. gondii were collected between 1991 and 2008 from 358 adult subjects with DSM-5 intermittent explosive disorder (IED), non-IED psychiatric disorders (psychiatric controls), or no evidence of any psychiatric diagnosis (healthy controls). Assessments of aggression, anger, and impulsivity, as well as state/trait anger, depression, and anxiety were completed. T. gondii seropositive status (IgG > 12 IU) was the primary outcome measure for this study.
Results: T. gondii seropositive status (IgG > 12 IU) was associated with higher aggression (P = .022) and impulsivity (P = .05) scores. When both aggression and impulsivity scores were controlled for, however, only aggression scores were higher in seropositive subjects (P = .011). In addition, T. gondii seropositive status and marginal mean +/- SE aggression scores increased from healthy controls (9.1% and -0.66 +/- 0.05) to psychiatric controls (16.7% and -0.27 +/- 0.05) to subjects with IED (21.8% and 1.15 +/- 0.06; P = .05). These findings were not accounted for by the presence of other syndromal/personality disorders or by states or traits related to depressed or anxious moods.
Conclusions: These data are consistent with previous studies suggesting a relationship between T. gondii and self-directed aggression (ie, suicidal behavior) and further add to the biological complexity of impulsive aggression both from a categorical and a dimensional perspective.
Possible link between Toxoplasma gondii infection and mood disorders in Lorestan Province, Western Iran
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Kheirandish, F., Nazari, H., Mahmoudvand, H., Yaseri, Y., Tarahi, M. J., Fallahi, S., Ezatpour, B.
Archives of Clinical Infectious Diseases 2016; 11.
Kheirandish, F., Nazari, H., Mahmoudvand, H., Yaseri, Y., Tarahi, M. J., Fallahi, S., Ezatpour, B.
Archives of Clinical Infectious Diseases 2016; 11.
Click for abstract
Background: A large number of epidemiological evidence in humans and experimental studies in rodents have hypothesized that Toxoplasma gondii is a potentially relevant etiological factor in some mood disorders.
Objectives: The aim of this study was to investigate whether latent toxoplasmosis has any role in mood disorders such as schizophrenia and bipolar disease in Western Iran.
Patients and Methods: A total of 170 patients including 85 schizophrenia and 85 bipolar patients referred to the only psychiatric hospital in Lorestan province in Khorramabd city, Western Iran, and 170 healthy volunteers were screened for IgG and IgM anti-T. gondii antibodies by the Enzyme Linked Immunosorbent Assay (ELISA). Structured questionnaires were used to obtain information on risk factors for T. gondii infection.
Results: Out of the 170 psychiatric patients, 103 (63.5%) patients were seropositive for IgG antibody and 14 (8.2%) were seropositive for IgM antibody. Of the 85 bipolar patients, 54 (63.5%) and 6 (7%) were found positive for anti-T. gondii IgG and IgM antibodies, respectively; whereas among 85 schizophrenia patients, 49 (57.6%) and 8 (9.4%) samples were found positive for anti-T. gondii IgG and IgM antibodies, respectively. From 170 healthy volunteers, 73 (42.9%) tested seropositive for anti-T. gondii antibodies; 65 (38.2%) tested seropositive for IgG antibody and 8 (4.7%) tested seropositive for IgM antibody. There was a significant difference in T. gondii IgG positivity between the psychiatric patients and control groups (P = 0.009). Several risk factors, which were significantly related to T. gondii seropositivity in psychiatric patients are being in contact with cats (P = 0.004), eating unwashed raw vegetables (P < 0.001), raw-milk/egg consumption (P = 0.001), and drinking clean water (P = 0.035).
Conclusions: We concluded that psychiatric patients in general and schizophrenia and bipolar cases in particular had a significantly higher relative frequency of T. gondii infection than healthy individuals of Lorestan Province, Western Iran.
Reciprocal moderation by Toxoplasma gondii seropositivity and blood phenylalanine – tyrosine ratio of their associations with trait aggression
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Mathai, A. J., Lowry, C. A., Cook, T. B., Brenner, L. A., Brundin, L., Groer, M. W., Peng, X. Q., Giegling, I., Hartmann, A. M., Konte, B., Friedl, M. Fuchs, D. Rujescu, D. Postolache, T. T.
Pteridines 2016; 27: 77-85.
Mathai, A. J., Lowry, C. A., Cook, T. B., Brenner, L. A., Brundin, L., Groer, M. W., Peng, X. Q., Giegling, I., Hartmann, A. M., Konte, B., Friedl, M. Fuchs, D. Rujescu, D. Postolache, T. T.
Pteridines 2016; 27: 77-85.
Click for abstract
We previously reported that trait aggression, proposed as an endophenotype for suicidal behavior, is positively associated with Toxoplasma gondii (T. gondii) seropositivity in females, but not in males. Additionally, older males seropositive for T. gondii had lower scores on measures of trait aggression, including self-aggression. Trait aggression may be influenced by dopaminergic signaling, which is known to be moderated by gender and age, and potentially enhanced in T. gondii positives through the intrinsic production of dopamine by the microorganism. Therefore, we investigated associations between trait aggression and interactions between T. gondii enzyme-linked immunoabsorbant assay (ELISA) IgG titer-determined seropositivity and high-performance liquid chromatography-(HPLC-) measured blood levels of dopamine precursors phenylalanine (Phe), tyrosine (Tyr), and their ratio in a sample of 1000 psychiatrically healthy participants. Aggressive traits were assessed using the questionnaire for measuring factors of aggression (FAF), the German version of the Buss-Durkee hostility questionnaire. We found that 1) the decrease in trait aggression scores in T. gondii-positive older males was only present in individuals with a low Phe:Tyr ratio, and 2) that there was a positive correlation between Phe: Tyr ratio and total aggression and selected subscales of aggression in T. gondii-positive males, but not in T. gondii-negative males. These findings point toward a gender-specific reciprocal moderation by Phe: Tyr ratio and T. gondii seropositivity of their associations with aggression scores, and lead to experimental interventions geared to manipulating levels of dopamine precursors in selected T. gondii positive individuals with increased propensity for aggression.
The relation of Toxoplasma infection and sexual attraction to fear, danger, pain and submissiveness
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Flegr, J., Kuba, R.
Evolutionary Psychology 2016; 1-10, DOI: 10.1177/1474704916659746
Flegr, J., Kuba, R.
Evolutionary Psychology 2016; 1-10, DOI: 10.1177/1474704916659746
Click for abstract
Behavioral patterns, including sexual behavioral patterns, are usually understood as biological adaptations increasing the fitness of
their carriers. Many parasites, so-called manipulators, are known to induce changes in the behavior of their hosts to increase their
own fitness. Such changes are also induced by a parasite of cats,
Toxoplasma gondii.
The most remarkable change is the fatal
attraction phenomenon, the switch of infected mice’s and rat’s native fear of the smell of cats toward an attraction to this smell.
The stimuli that activate fear-related circuits in healthy rodents start to also activate sex-related circuits in the infected animals.
An analogy of the fatal attraction phenomenon has also been observed in infected humans. Therefore, we tried to test a
hypothesis that sexual arousal by fear-, violence-, and danger-related stimuli occurs more frequently in
Toxoplasma
-infected
subjects. A cross-sectional cohort study performed on 36,564 subjects (5,087
Toxoplasma
free and 741
Toxoplasma
infected)
showed that infected and noninfected subjects differ in their sexual behavior, fantasies, and preferences when age, health, and the
size of the place where they spent childhood were controlled (
F
(24, 3719)
¼
2.800,
p
< .0001). In agreement with our a priori
hypothesis, infected subjects are more often aroused by their own fear, danger, and sexual submission although they practice
more conventional sexual activities than
Toxoplasma
-free subjects. We suggest that the later changes can be related to a decrease
in the personality trait of novelty seeking in infected subjects, which is potentially a side effect of increased concentration of
dopamine in their brain.
Assessment of toxoplasma seropositivity in children suffering from attention deficit hyperactivity disorder
Afsharpaiman, S., Khosravi, M.H., Faridchehr, M., Komijani, M., Radfar, S., Amirsalari, S., Torkaman, M., Shirbazoo, S.
Galen Medical Journal 2016; 5: 188-193
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Background: Toxoplasmosis, a protozoan infection caused by Toxoplasma gondii, is suggested to be a risk factor for many psychological disorders such as schizophrenia and depression. Attention deficit hyperactivity disorder (ADHD) is one of the most common psychiatric disorders among children. Previous studies have assessed the correlation between ADHD and infectious diseases like toxoplasmosis. So we aimed to investigate the possible correlation between Toxoplasma seropositivity and ADHD in children. Materials and Methods: In this cross-sectional study children with signs of ADHD were regarded as patients and underwent clinical assessments. Diagnosis of these patients was based on DSM-IV-TR system which was performed by a pediatric psychiatrist. Forty-eight Children without signs of ADHD or other psychic disorders were considered as control, and 48 patients were considered as case group. Parents were asked to answer a questionnaire including demographic, pregnancy and habitual questions. Blood samples were taken from all individuals and assessed for anti-Toxoplasma IgM and IgG antibodies. Results: Ninety-six male and female patients with a mean age of 8.12 years underwent analysis. Seropositivity rate for anti-T.gondii IgG antibody was 4.2% in the case and 2.1% in control individuals (P=0.92). Anti-T.gondii IgM antibodies were not found in control individuals while it was found in 2.1% of case individuals (P=0.74). There was no statistically significant association between seroprevalence of IgM (P=0.74) and IgG (P=0.92) antibodies and ADHD in study individuals. Conclusion: Our findings showed that the toxoplasmosis seropositivity has no significant difference between children with and without ADHD. Further studies are needed with a larger amount of individuals.
Relationship between Toxoplasma gondii and mood disturbance in women veterans
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Duffy, A. R., Beckie, T. M., Brenner, L. A., Beckstead, J. W., Seyfang, A., Postolache, T. T., Groer, M. W.
Military Medicine 2015; 180: 621-625.
Duffy, A. R., Beckie, T. M., Brenner, L. A., Beckstead, J. W., Seyfang, A., Postolache, T. T., Groer, M. W.
Military Medicine 2015; 180: 621-625.
Click for abstract
Background: Toxoplasma gondii is an intracellular protozoan parasite with zoonotic potential that causes acute and chronic diseases, which has been associated with schizophrenia, depression, bipolar disorder, and suicidal behavior. Military personnel may be at increased risk for exposure to the parasite when deployed to countries with high prevalence rates. Methods: Women Veterans were recruited to participate in the study at an event to recognize women Veterans and later through e-mails. Blood samples were collected from 70 women Veterans (mean age: 47 years) and analyzed for T. gondii IgG titer. Participants completed a demographic instrument, Center for Epidemiologic Studies Depression scale, Profile of Mood States (POMS), and Post-Traumatic Stress Disorder Checklist-Military. Results: The infectivity rate was lower than the rate in the United States (11.4% [8 out of 70 were seropositive], but 6 of the 8 [75%] had been deployed outside the United States. Pearson correlations and t tests showed significant relationships between T. gondii seropositivity and Center for Epidemiologic Studies Depression score), POMS-depression, POMS-confusion, and POMS-anger subscale scores, and total mood disturbance score. Conclusions: This study is the first to describe biobehavioral relationships between chronic T. gondii infection, depression, and dysphoric moods in a military veteran population
Toxoplasma gondii and anxiety disorders in a community-based sample
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Markovitz, A. A., Simanek, A. M., Yolken, R. H., Galea, S., Koenen, K. C., Chen, S., Aiello, A. E.
Brain Behavior and Immunity 2015; 43: 192-197
Markovitz, A. A., Simanek, A. M., Yolken, R. H., Galea, S., Koenen, K. C., Chen, S., Aiello, A. E.
Brain Behavior and Immunity 2015; 43: 192-197
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A growing body of literature suggests that exposure to the neurotropic parasite Toxoplasma gondii (T. gondii) is associated with increased risk of mental disorders, particularly schizophrenia. However, a potential association between T. gondii exposure and anxiety disorders has not been rigorously explored. Here, we examine the association of T. gondii infection with both anxiety and mood disorders. Participants (n = 484) were drawn from the Detroit Neighborhood Health Study, a population-representative sample of Detroit residents. Logistic regression was used to examine the associations between T. gondii exposure (defined by seropositivity and IgG antibody levels) and three mental disorders: generalized anxiety disorder (GAD), posttraumatic stress disorder (PTSD) and depression. We found that T. gondii seropositivity was associated with a 2 times greater odds of GAD (odds ratio (OR). 2.25: 95% confidence interval (CI), 1.11-4.53) after adjusting for age, gender, race, income, marital status, and medication. Individuals in the highest antibody level category had more than 3 times higher odds of GAD (OR, 3.35: 95% Cl, 1.41-7.97). Neither T. gondii seropositivity nor IgG antibody levels was significantly associated with PTSD or depression. Our findings indicate that T. gondii infection is strongly and significantly associated with GAD. While prospective confirmation is needed, T. gondii infection may play a role in the development of GAD.
Effect of toxoplasmosis on personality profiles of Iranian men and women
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Khademvatan, S., Khajeddin, N., Saki, J., Izadi-Mazidi, S.
South African Journal of Science 2013; 109: 92-95
Khademvatan, S., Khajeddin, N., Saki, J., Izadi-Mazidi, S.
South African Journal of Science 2013; 109: 92-95
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There is evidence to suggest that the protozoan Toxoplasma gondii, which causes toxoplasmosis, changes the personality of people who are infected with it. The aim of this study was to compare the personality characteristics of Iranian students with and without latent toxoplasmosis. A total of 237 students (111 men and 126 women) of Jundishapur University of Medical Sciences (Ahvaz, Iran) were tested for the presence of anti-Toxoplasma antibodies and completed demographic questionnaires and Cattell's 16 Personality Factor Questionnaire. Data were analysed using multiple univariate analyses of variance. Women with latent toxoplasmosis had a significantly different personality profile from women without toxoplasmosis, namely higher O (apprehension), N (privateness) and Q(4) (tension) scores, and lower Q(1) (openness to change) scores. Infected men had significantly higher L (vigilance, mistrust) scores compared to non-infected men. Factors E (dominance) and Q(1) (openness to change) tended to be higher in infected men than non-infected men but the difference was not quite statistically significant. Our findings have, for the first time, independently confirmed that personality profile is affected by latent toxoplasmosis.
Toxoplasmosis-associated difference in intelligence and personality in men depends on their Rhesus blood group but not ABO blood group
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Flegr, J., Preiss, M., Klose, J.
PLoS ONE 2013; 8(4): e61272. doi:10.1371/journal.pone.0061272
Flegr, J., Preiss, M., Klose, J.
PLoS ONE 2013; 8(4): e61272. doi:10.1371/journal.pone.0061272
Click for abstract
Background:
The parasite
Toxoplasma gondii
influences the behaviour of infected animals and probably also personality of
infected humans. Subjects with a Rhesus-positive blood group are protected against certain behavioural effects associated
with
Toxoplasma
infection, including the deterioration of reaction times and personality factor shift.
Methodology/Principal Findings:
Here, we searched for differences in the toxoplasmosis-associated effects between RhD-
positive and RhD-negative subjects by testing 502 soldiers with two personality tests and two intelligence tests. The
infected subjects expressed lower levels of all potentially pathognomic factors measured with the N-70 questionnaire and in
neurasthenia measured with NEO-PI-R. The RhD-positive,
Toxoplasma
-infected subjects expressed lower while RhD-
negative,
Toxoplasma
-infected subjects expressed higher intelligence than their
Toxoplasma
-free peers. The observed
Toxoplasma
-associated differences were always larger in RhD-negative than in RhD-positive subjects.
Conclusions:
RhD phenotype plays an important role in the strength and direction of association between latent
toxoplasmosis and not only psychomotor performance, but also personality and intelligence
Association between Toxoplasma gondii infection and TCI personality traits
Kamal, S. A., Sleemi, A., Ashraf, A., Hinman, S. J., Giegling, I., Hartmann, A. M., Konte, B., Friedl, M., Rujescu, D., Postolache, T. T.
Biological Psychiatry 2013; 73: 280-280
Higher extraversion and lower conscientiousness in humans infected with Toxoplasma
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Lindová, J., Příplatová, L., Flegr, J.
European Journal of Personality 2012; 26: 285–291
Lindová, J., Příplatová, L., Flegr, J.
European Journal of Personality 2012; 26: 285–291
Click for abstract
oxoplasmosis is associated with speci
fi
c differences in the personality
of infected subjects relative to
non-infected subjects. These differences are usually cons
idered to be a side effect of the manipulative activity of
the parasite aimed to increase the probability of its
transmission from the intermediate host to the de
fi
nitive host
by predation. The personality of infected s
ubjects was studied mostly using the Cattell
’
s questionnaire. However,
this questionnaire is now considered outdated and has been mostly substituted with the Neuroticism
–
Extraversion
–
Openness Personality Inventory
—
Revised (NEO-PI-R) questionnaire in clinical practice. Here, we searched for the as-
sociation between toxoplasmosis and the personality by screening a population of students with the NEO-PI-R question-
naire. We found that Toxoplasma-infected male and female students had signi
fi
cantly higher extraversion and lower
conscientiousness. The conscientiousness negatively correlated with the length of infection in men, which suggested that
the toxoplasmosis associated differences were more probably the result of slow cumulative changes induced by latent
toxoplasmosis, rather than transient side effect of acute Toxoplasma infection. The existence of this correlation also sup-
ported (but of course not proved) the hypothesis that Toxoplasma infection in
fl
uenced the personality, rather than the
hypothesis that the personality in
fl
uenced the probability of the infection.
Toxoplasma gondii associated behavioural changes in mice, rats and humans: Evidence from current research
Bech-Nielsen, S.
Preventive Veterinary Medicine 2012; 103: 78-79
Rhesus factor modulation of effects of smoking and age on psychomotor performance, intelligence, personality profile, and health in Czech soldiers
Flegr, J., Geryk, J., Volny, J., Klose, J., Cernochova, D.
Plos One 2012; 7: ARTN e49478 10.1371/journal.pone.0049478
Click for abstract
Background: Rhesus-positive and rhesus-negative persons differ in the presence-absence of highly immunogenic RhD protein on the erythrocyte membrane. This protein is a component of NH3 or CO2 pump whose physiological role is unknown. Several recent studies have shown that RhD positivity protects against effects of latent toxoplasmosis on motor performance and personality. It is not known, however, whether the RhD phenotype modifies exclusively the response of the body to toxoplasmosis or whether it also influences effects of other factors.
Methodology/Principal Findings: In the present cohort study, we searched for the effects of age and smoking on performance, intelligence, personality and self-estimated health and wellness in about 3800 draftees. We found that the positive effect of age on performance and intelligence was stronger in RhD-positive soldiers, while the negative effect of smoking on performance and intelligence was of similar size regardless of the RhD phenotype. The effect of age on four Cattell's personality factors, i.e., dominance (E), radicalism (Q(1)), self-sentiment integration (Q(3)), and ergic tension (Q(4)), and on Cloninger's factor reward dependency (RD) was stronger for RhD-negative than RhD-positive subjects, while the effect of smoking on the number of viral and bacterial diseases was about three times stronger for RhD-negative than RhD-positive subjects.
Conclusions: RhD phenotype modulates the influence not only of latent toxoplasmosis, but also of at least two other potentially detrimental factors, age and smoking, on human behavior and physiology. The negative effect of smoking on health (estimated on the basis of the self-rated number of common viral and bacterial diseases in the past year) was much stronger in RhD-negative than RhD-positive subjects. It is critically needed to confirm the differences in health response to smoking between RhD-positive and RhD-negative subjects by objective medical examination in future studies.
The relation of cortisol and sex hormone levels to results of psychological, performance, IQ and memory tests in military men and women
Flegr, J., Hampl, R., Černochová, D., Preiss, M., Bičíkova, M., Sieger, L., Příplatová, L., Kaňková, S., Klose, J.
Neuroendocrinology Letters 2012; 33: 224-235
Click for abstract
BACKGROUND: Cortisol, along with other hormones of hypothalamo-pituitary-adrenal axis, belongs to one of the main factors influencing psychological and pathognomic factors, intelligence, and memory.
METHODS: The aim of our study was to review a large battery of psychological, performance, IQ and memory tests as to their relation with cortisol, testosterone and estrogen levels in groups of 100 men and 93 women who attended the Central Military Hospital in Prague for regular entrance psychological examinations for military personnel.
RESULTS: In men, we detected positive correlations between cortisol and emotional lability, and negative correlations with impulsivity, while in women hypochondria and psychopathology were negatively correlated, and aggression measured with the Meili selective memory test had a positive relation to cortisol level. Testosterone correlated positively with emotional liability and negatively with impulsivity in men, and negatively with hypochondria and psychasteny, indirect aggression, irritability and paranoia in women. Estradiol correlated positively with psychopathology in men, and negatively with phobia. It was positively correlated with negativism in women. No clear correlation was observed between the concentration of steroid hormones and psychomotor performance or intelligence.
CONCLUSIONS: Concentrations of steroid hormones correlate with results of several psychological tests, the sign and magnitude of these correlations, however, very often differ in military men and women.
Pattern of money allocation in experimental games supports the stress hypothesis of gender differences in Toxoplasma gondii-induced behavioural changes
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Lindová, J., Kubena, A.A., Sturcová, H., Krivohlavá, R., Novotná, M., Rubesová, A., Havlícek, J., Kodym, P. , Flegr, J.
Folia Parasitologica 2010; 57: 136-142
Lindová, J., Kubena, A.A., Sturcová, H., Krivohlavá, R., Novotná, M., Rubesová, A., Havlícek, J., Kodym, P. , Flegr, J.
Folia Parasitologica 2010; 57: 136-142
Click for abstract
Latent toxoplasmosis has been previously found to cause behavioural and personality changes in humans, which are
specific for each gender. Here we tested the stress hypothesis of these gender differences based on the assumption that latent toxo
-
plasmosis causes long-term subliminal stress. In line with this hypothesis, the gender difference will appear specifically in situations
with interpersonal context because in contrast to the typical individualistic coping style of men, women have a tendency to express
elevated prosocial behaviour under stress. Altogether 295 biology students (29/191 females and 27/104 males infected by
T. gondii
)
played a modified version of the Dictator Game and the Trust Game. As predicted, a gender difference in the effect of latent toxo
-
plasmosis was found for the measure of reciprocal altruism in the Trust Game (
p
= 0.016), but both genders appeared less generous
when infected in the Dictator Game modified to minimize social connotation (
p
= 0.048).
The influence of RhD phenotype on toxoplasmosis- and age-associated changes in personality profile of blood donors
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Flegr, J., Novotná, M., Fialová, A., Kolbeková, P., Gasová, Z.
Folia Parasitologica 2010; 57: 57: 143-150
Flegr, J., Novotná, M., Fialová, A., Kolbeková, P., Gasová, Z.
Folia Parasitologica 2010; 57: 57: 143-150
Click for abstract
Toxoplasma gondii
, a parasite infecting 20–60% of humans in various countries, influences the behaviour of infected
animal and human hosts. Infected human subjects have changes in several of Cattell’s and Cloninger’s personality factors. Recently,
three independent studies have shown that Rh-positive subjects are protected against the
T. gondii
-induced changes of reaction times
and increased risk of traffic accidents. Here we searched for evidence of similar effects of RhD phenotype on toxoplasmosis- or
aging-associated changes in the personality profile of about 302 blood donors. We found that Rh-positive and Rh-negative subjects
responded differently to toxoplasmosis. In addition to the already known effects of toxoplasmosis on novelty seeking, self transcend
-
ence, superego strength and protension, we also found effects of RhD phenotype on ego strength, protension, and praxernia, as well
as opposite effects of toxoplasmosis on ego strength, praxernia, ergic tension and cooperativeness in Rh-positive and Rh-negative
subjects. Moreover, our results indicate that RhD phenotype might influence not only the effect of toxoplasmosis but also the effect
of aging on specific personality traits.
Higher perceived dominance in Toxoplasma infected men – a new evidence for role of increased level of testosterone in toxoplasmosis-associated changes in human behavior
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Hodková, H., Kolbeková, P., Skallová, A., Lindová, J. , Flegr, J.
Neuroendocrinology Letters 2007; 28: 110-114
Hodková, H., Kolbeková, P., Skallová, A., Lindová, J. , Flegr, J.
Neuroendocrinology Letters 2007; 28: 110-114
Click for abstract
Toxoplasma
is parasite of cats that uses any warm-blooded animals as intermediate
hosts. It is known to induce shifts in behavior, physiology and even morphology
of its intermediate hosts, including humans. The lower second to fourth digit ratio
(2D:4D ratio) in infected man and women, and higher height in infected man sug
-
gest that sex steroid hormones like testosterone could play a role in these shifts.
Here, we searched for another indirect indication for a higher postnatal testosterone
level, i.e. increased perceived dominance and masculinity in infected men. We
showed portrait pictures of 89 male students of which 18 were
Toxoplasma
-
infected to 109 female students. When we statistically corrected for age, men with
latent toxoplasmosis were perceived as more dominant (p=0.009) and masculine
(p=0.052). These results support the idea that the higher level of testosterone could
be responsible for at least some of the toxoplasmosis-associated shifts in human and
animal behavior.
Effects of Toxoplasma on human behavior
Click for abstract
Although latent infection with
Toxoplasma gondii
is among
the most prevalent of human infections, it has been gener-
ally assumed that, except for congenital transmission, it is
asymptomatic. The demonstration that latent
Toxoplasma
infections can alter behavior in rodents has led to a recon-
sideration of this assumption. When infected human adults
were compared with uninfected adults on personality ques-
tionnaires or on a panel of behavioral tests, several differ-
ences were found. Other studies have demonstrated reduced
psychomotor performance in affected individuals. Possible
mechanisms by which
T. gondii
may affect human behavior
include its effect on dopamine and on testosterone.
Can the common brain parasite, Toxoplasma gondii, influence human culture?
Lafferty, K.D.
Proceedings of the Royal Society B-Biological Sciences 2006; 273: 2749-2755.
Click for abstract
The latent prevalence of a long-lived and common brain parasite, Toxoplasma gondii, explains a statistically significant portion of the variance in aggregate neuroticisin among populations, as well as in the 'neurotic' cultural dimensions of sex roles and uncertainty avoidance. Spurious or non-causal correlations between aggregate personality and aspects of climate and culture that influence T gondii transmission could also drive these patterns. A link between culture and T gondii hypothetically results from a behavioural manipulation that the parasite uses to increase its transmission to the next host in the life cycle: a cat. While latent toxoplasmosis is usually benign, the parasite's subtle effect on individual personality appears to alter the aggregate personality at the population level. Drivers of the geographical variation in the prevalence of this parasite include the effects of climate on the persistence of infectious stages in soil, the cultural practices of food preparation and cats as pets. Some variation in culture, therefore, may ultimately be related to how climate affects the distribution of T gondii, though the results only explain a fraction of the variation in two of the four cultural dimensions, suggesting that if T gondii does influence human culture, it is only one among many factors.
Gender differences in behavioural changes induced by latent toxoplasmosis
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Lindová, J., Novotná, M., Havlícek, J., Smídová, E., Skallová, A., Kolbeková, P., Hodný, Z., Kodym, P. , Flegr, J.
International Journal for Parasitology 2006; 36: 1485-1492
Lindová, J., Novotná, M., Havlícek, J., Smídová, E., Skallová, A., Kolbeková, P., Hodný, Z., Kodym, P. , Flegr, J.
International Journal for Parasitology 2006; 36: 1485-1492
Click for abstract
There is growing evidence that the protozoan
Toxoplasma gondii
modifies behaviour of its intermediate hosts, including humans,
where it globally infects about 20–60% of the population. Although it is considered asymptomatic in its latent stage, it was previously
found to have remarkable and gender different effects on the personality factors A (warmth), G (rule consciousness), L (vigilance, mis-
trust) and Q3 (self-control, self-image) from Cattell’s 16PF Questionnaire. We performed a double blind experiment testing 72 and 142
uninfected men and women, respectively, and 20 and 29 infected men and women, respectively, in order to verify these gender differences
using behavioural experiments. Our composite behavioural variables Self-Control and Clothes Tidiness (analogue to the 16PF factors G
– conscientiousness and Q3 – self-control) showed a significant effect of the toxoplasmosis–gender interaction with infected men scoring
significantly lower than uninfected men and a trend in the opposite direction in women. The effect of the toxoplasmosis–gender inter-
action on our composite behavioural variable Relationships (analogue to factor A – warmth) approached significance; infected men
scored significantly lower than uninfected men whereas there was no difference in women. In the composite behavioural variable Mistrust
(analogue to factor L), the pattern was affected by environment (rural versus urban). Possible interpretations of the gender differences are
discussed.
Look what the cat dragged in: do parasites contribute to human cultural diversity?
Lafferty, K.D.
Behavioural Processes 2005; 68: 279-282
Decreased level of novelty seeking in blood donors infected with Toxoplasma
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Skallová, A., Novotná, M., Kolbeková, P., Gasová, Z., Veselý,V., Sechovská, M., Flegr, J.
Neuroendocrinology Letters 2005; 26: 480-486
Skallová, A., Novotná, M., Kolbeková, P., Gasová, Z., Veselý,V., Sechovská, M., Flegr, J.
Neuroendocrinology Letters 2005; 26: 480-486
Click for abstract
OBJECTIVES
:
Toxoplasma gondii
, a parasitic protozoan, infects about 30–60% of
people worldwide.
Toxoplasma
is known to induce behavioral changes and an
increase of dopamine in mice. The presence of anti-
Toxoplasma
antibodies (latent
toxoplasmosis) is also a risk factor for schizophrenia. Latent toxoplasmosis in
men (male soldiers) is associated with lower novelty seeking. As the novelty seek
-
ing is supposed to negatively correlate with level of dopamine, the observed effect
was interpreted as indirect evidence of increased dopamine levels in subjects with
toxoplasmosis. However, it is also possible that the observed effect was caused by
association of both novelty seeking and
Toxoplasma
infection with a third factor,
e.g. size of place of residence.
METHODS
:
Personality profile of 290 blood donors (205 men and 85 women) were
measured by Cloninger’s TCI (Temperament and Character Inventory) and their
blood samples were assayed for the presence of anti-
Toxoplasma
antibodies. Dif
-
ference between
Toxoplasma
-infected and
Toxoplasma
-free subjects was tested
with ANCOVA method with gender, size of place of residence, and age as covari
-
ates.
RESULTS
:
The present analysis revealed that lower novelty seeking was associ
-
ated with latent toxoplasmosis both in men and women. The effect of infection
on novelty seeking remained significant even after adjustment for size of place of
residence (p<0.0).
CONCLUSION
:
Decreased novelty seeking in
Toxoplasma
-infected subjects have
been already confirmed in three independent populations (male soldiers and
male and female blood donors). These findings suggest that the local inflamma
-
tion-induced increase in dopamine in the brain of infected subjects can represent
a missing link between toxoplasmosis and schizophrenia
Probable neuroimmunological link between Toxoplasma and cytomegalovirus infections and personality changes in the human host
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Novotná, M., Hanusova, J, Klose J., Preiss, M., Havlicek, J., Roubalová, K., Flegr, J.
BMC Infectious Diseases 2005; 5: 54
Novotná, M., Hanusova, J, Klose J., Preiss, M., Havlicek, J., Roubalová, K., Flegr, J.
BMC Infectious Diseases 2005; 5: 54
Click for abstract
Background:
Recently, a negative
association between
Toxoplasma
-infection and novelty s
eeking was reported. The
authors suggested that changes of pers
onality trait were caused by manipula
tion activity of the parasite, aimed at
increasing the probability of tr
ansmission of the parasite from an intermedia
te to a definitive host
. They also suggested
that low novelty seeking indicated an in
creased level of the neurot
ransmitter dopamine in the
brain of infected subjects,
a phenomenon already observ
ed in experimentally infected ro
dents. However, the changes in
personality can also be just
a byproduct of any neurotropic infection
. Moreover, the association between a pe
rsonality trait and
the toxoplasmosis
can even be caused by an independent
correlation of both the probability of
Toxoplasma
-infection and the personality
trait with the third factor, namely with th
e size of living place of a subject. To
test these two alternative hypotheses, we
studied the influence of another neurotropic pathogen, the cyto
megalovirus, on the personali
ty of infected subjects, and
reanalyzed the original data after the
effect of the potential confounder, the si
ze of living plac
e, was controlled.
Methods:
In the case-control study, 533 conscr
ipts were tested for to
xoplasmosis and presence
of anti-cytomegalovirus
antibodies and their novelty se
eking was examined with Cloninger's TCI questionnaire. Possible association between the
two infections and TCI dimensions was analyzed.
Results:
The decrease of novelty seeking is as
sociated also with cytomegalovirus infe
ction. After the size of living place
was controlled, the effect of to
xoplasmosis on novelty seeking increased. Si
gnificant difference in novelty seeking was
observed only in the largest city, Prague.
Conclusion:
Toxoplasma
and cytomegalovirus probably induce a decrease
of novelty seeking.
As the cytomegalovirus
spreads in population by direct contact (not by predation as with
Toxoplasma
), the observed changes are the byproduct
of brain infections rather than
the result of manipulation activity of a parasite
. Four independent line
s of indirect evidence,
namely direct measurement of neurotransmi
tter concentration in mice, the nature of
behavioral changes in rodents, the
nature of personality changes in humans, and the observed
association between schizophren
ia and toxoplasmosis, suggest
that the changes of dopamine concentration in brain coul
d play a role in behavioral changes of infected hosts.
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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Flegr, J., Preiss, M., Klose, J., Havlíček, J., Vitáková, M, Kodym, P.
Biological Psychology 2003; 63: 253-268
Flegr, J., Preiss, M., Klose, J., Havlíček, J., Vitáková, M, Kodym, P.
Biological Psychology 2003; 63: 253-268
Click for 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. Howe
v
er, infected subjects score worse in psychomotor performance
tests and ha
v
e different personality profiles than
Toxoplasma
-negati
v
e subjects. The
mechanism of this effect is unknown; howe
v
er, 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
-positi
v
e and
Toxoplasma
-
negati
v
e subjects by testing 857 military conscripts using a modern psychobiological
questionnaire, namely with Cloninger’s Temperament and Character In
v
entory (TCI).
ANCOVA showed that
Toxoplasma
-positi
v
e subjects had lower No
v
elty seeking (NS) scores(
P
/
0.035) and lower scores for three of its four subscales, namely Impulsi
v
eness (
P
/
0.049),
Extra
v
agance (
P
/
0.056) and Disorderliness (
P
/
0.006) than the
Toxoplasma
-negati
v
e
subjects. Differences between
Toxoplasma
-negati
v
e and positi
v
e subjects in NS was in
v
ersely
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 achie
v
ing a higher education (
P
2
B
/
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
Correlation of duration of latent Toxoplasma gondii infection with personality changes in women
Click for abstract
Many parasites induce characteristic changes in behavior of their hosts. In humans latent
toxoplasmosis is associated with changes in personality profiles. It has been already shown
that a decrease in superego strength is correlated with duration of toxoplasmosis in men.
Here we studied changes in personality profiles with Cattell’s 16 PF questionnaire in
Toxoplasma
-infected women. The changes were measured as differences in personality
factors between
Toxoplasma
-infected subjects and uninfected controls of the same age. The
low-rate changes were studied in 230 women diagnosed with acute toxoplasmosis during past
14 years. The results showed the correlation between duration of toxoplasmosis and level of
factors G (high superego strength) and Q3 (high strength of self sentiment). The high-rate
changes were estimated by measuring the correlation between level of
Toxoplasma
-antibody
titers (which rapidly decline after the end of acute phase of toxoplasmosis) and personality
factors in an experimental set of 55 young mothers with latent toxoplasmosis. Again, certain
factors, namely A (affectothymia), F (surgence), G (high superego strength), H (parmia), and
L (protension), correlated with the length of the infection. We suggest that the parasite
induced the changes in the personality profiles of the women because of our observation of
an increasingly different personality profile over time between women with latent infection
and controls. The same evidence questions the view that women with a particular personality profile are more prone to acquisition
Differences in personality profiles of Toxoplasma gondii infected and uninfected biologist
Click for abstract
Parasitic protozoan Toxoplasma gondii induces specific changes the behavior of its intermediate hosts. Human latent toxoplasmosis (presence of anti-Toxoplasma immunity in subjects without any clinical symptoms of acute toxoplasmosis) is known to be associated with specific changes of personality profiles of infected subjects. I the present work we studied the toxoplasmosis-associated differences in personality profiles (monitored by Cattell's 16PF questionnaire) in a population of 443 university students and teachers of biology. Our results show that the factors A, G, L, N and Q3 were shifted in the opposite direction in men and women; the factor O was shifted in the same direction, however, the intensity of the shift in women was relatively low. The men with latent toxoplasmosis had lower factor G (had higher tendency to disregard rules) p=0.049, higher factor L (were more suspecting, jealous, dogmatic) p=0.015, and higher factor O (were more apprehensive, self-reproaching, insecure) p=0.046. The Toxoplasma-infected women had higher factor A (warm-hearted, outgoing, easygoing) p=0.001. Several personality factors were shifted (both in men and women) from extreme values toward the middle of the psychological scales. Therefore, the Toxoplasma-infected subjects expressed less extreme personality attitudes in factors F, M, Q1 and Q4.
Changes in personality profile of young women with latent toxoplasmosis
Click for abstract
Abstract.
Latent toxoplasmosis is the most widesp
read parasite infection in developed
and developing countries. The prevalence
of
Toxoplasma gondii
infection varies mostly between 20 to 80% in differe
nt territories. This form
of toxoplasmosis is generally
considered to be asymptomatic. Recently
published results, however, suggest that the
personality profiles of infected subjects
differ
from those of uninfected controls. Th
ese results, however, were obtained on
non-standard populations (biologists or former acute
toxoplasmosis patients). Here we studied the pers
onality profiles of 191 young women tested for anti-
Toxoplasma
immunity during
gravidity. The results showed
that the differences between
Toxoplasma
-negative and
Toxoplasma
-positive subjects exits also in this
sample of healthy women. The subjects with
latent toxoplasmosis had higher intelligence, lower guilt proneness, and possibly al
so
higher ergic tension. The difference in several other factors (d
esurgency/surgency, alaxia/protension, naiveté/shrewdness, and
self-
sentiment integration) concerned changes in the vari
ances, rather than the mean
values of the factors.
Toxoplasmosis, behaviour and personality
Holliman, R. E.
Journal of Infection 1997; 35: 105-110
Click for abstract
The clinical sequelae of acute and congenital toxoplasmosis are well established, but that of chronic toxoplasma infection remains uncertain. In rodents, chronic toxoplasma infection is associated with altered behaviour leading to an enhanced risk of feline predation and a putative selective advantage to the parasite. It is proposed that neurotropic cysts of toxoplasma exert an effect on animal behaviour, either directly or via the release of metabolic products. Long-standing toxoplasma infection in humans has been linked to cerebral tumour formation and personality shift. In view of the vast population with chronic toxoplasma infection, further studies of the clinical sequelae of this condition are required.
Induction of changes in human behaviour by the parasitic protozoan Toxoplasma gondii
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Toxoplasma gondii, the coccidian parasite, is known to induce changes in the behaviour of its intermediate hosts. The high prevalence of this parasite in the human population (20-80%) offers the opportunity of studying the influence of the parasite on human behaviour by screening of a normal population.
Two hundred and twenty-four men and one hundred and seventy women were tested for toxoplasmosis and their personality profiles were measured by Cattell's questionnaire. Highly significant differences between Toxoplasma infected and uninfected subjects were observed (p < 0.01). For men the factors G (low superego strength, p<0.02), and possibly L (protension), O (guilt proneness), and A (sizothymia) prevailed in infected subjects. For women the prevailing factors were A (afectothymia, p<0.01), and possibly L (alaxia) and N (shrewdness). To reveal whether toxoplasmosis induces personality factor-shifts or whether certain combinations of personality factors influence the probability of acquiring Toxoplasma infection, we examined the personality profiles of 164 male patients diagnosed with acute toxoplasmosis during the past 13 years. The existence of a positive correlation between the duration of latent toxoplasmosis and the intensity of superego strength decrease (p<0.02) suggested that the decrease of superego strength (the willingness to accept group moral standards) was induced by T. gondii infection.
Influence chronic toxoplasmosis on some personality factors
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Abstract. An effect of parasites on host behaviour was tested on the toxoplasma-human model. Three hundred and thirty-eight (338)
people were assessed with Cattell's personality questionnaire and then tested for Toxoplasma gondii infection with a delayed type hypersensitivity
test for Toxoplasma. A highly significant correlation between chronic toxoplasmosis and two personality factors (G- Low
Superego Strength and L- Protension) was found (p =0.0032 and 0.0020, respectively). A correlation of the intensity of the personality
factor-shifts with the duration of the infection (estimated from antibody titer) suggests that toxoplasmosis induces the shift in human personality, rather than the personality factors G and L influence an acquisition rate of Toxoplasma gondii infection.