Can the common brain parasite, Toxoplasma gondii, influence human culture?

The latent prevalence of a long-lived and common brain parasite, Toxoplasma gondii, explains a statistically significant portion of the variance in aggregate neuroticism 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.

Country of birth and hospital admission rates for mental disorders: a cohort study of 4.5 million men and women in Sweden.

This study analysed the association between country of birth and psychotic, affective, and neurotic disorders in seven immigrant categories, after adjustment for demographic and socioeconomic factors. A 2-year national cohort study of 4.5 million individuals in the age group 25-64 years was performed. Swedish national registers including individual demographic and socioeconomic data were linked to the hospital discharge register. Cox regression was used in the analysis. Several groups of immigrants, both men and women, had risks of hospital admission for psychotic, affective, or neurotic disorders compared to the Swedish-born reference group. The impact of demographic and socioeconomic factors on these risks seemed to be larger for men than for women. For foreign-born men, several of the risks no longer remained significant after adjustment for income and marital status. In contrast, most of the risks for foreign-born women remained significant after adjustment for income and marital status. Low income and being single were associated with an increased risk of psychiatric hospital admission. These results represent important knowledge for clinicians and public health planners who are involved in treatment and prevention of mental disorders among certain groups of immigrants, and among low income men and women irrespective of immigrant status.

[Reactivity of toxoplasmin intradermal test in neurotic and manic-depressive patients]. / Reactividad a la prueba intradérmica con toxoplasmina en enformos neuróticos y psicóticos maniacodepresivos.

Fifty patients with manic-depressive psychosis, 120 neurotics and 100 healthy individuals were studied. They underwent the toxoplasmin intradermal test. The highest percentage of reactors was found among patients with manic-depressive psychosis (66,0%). Patients with depressive neurosis accounted for the highest number among neurotics (55,6%). The intensity of reaction was higher among patients with manic-depressive psychosis. Neurotic patients were compared to schizophrenic patients from a previous study conducted by one out of the authors. It is concluded that the percentage of reactors is higher among patients with depressive mental disorders, and also that this percentage increases with mental deterioration in patients.