MedicalResearch.com: What is the background for this study? What are the main findings?
Response: Our hypothesis was that people who grew up in cities with more than 100.000 inhabitants and without pets will show a more pronounced immune activation towards psychosocial stressors compared with people raised in rural areas in the presence of farm animals. This hypothesis is based on the fact that stress-associated psychiatric disorders, which are linked to or even promoted by an over(re)active immune system and chronic low grade inflammation, are more prevalent in urban compared with rural areas. One possible explanation for a hyper(re)active immune system in people raised in urban relative to rural environments might be a reduced contact to immunoregulatory microorganisms (the so called “old friends”), which is significantly increased in rural people with regular contact with farm animals compared with urban people in the absence of pets.
Our results show that a standardized laboratory psychosocial stressor causes a greater inflammatory response in young healthy participants with an urban upbringing in the absence of pets, relative to young healthy participants with a rural upbringing in the presence of farm animals.
MedicalResearch.com: What should clinicians and patients take away from your report?
Response: Together, our findings support the hypothesis that urban vs. rural upbringing in the absence or presence of animals, respectively, increases vulnerability to stress-associated physical and mental disorders by compromising adequate resolution of systemic immune activation following social stress and, in turn, aggravating stress-associated systemic immune activation. This is of particular importance, as urbanization and the associated socioeconomic consequences are increasing.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Response: We hope to expand the study to larger samples, women, and new locations and try to parse out how much of the benefit is coming from exposure to pets and how much is coming from rural living.
For now, the authors advise eating foods rich in healthy bacteria, or probiotics, spending time in nature and getting a furred pet. Although a lot of research still needs to be done, it looks as if spending as much time as possible, preferably during upbringing, in environments offering a wide range of microbial exposures has many beneficial effects.
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Till S. Böbel, Sascha B. Hackl, Dominik Langgartner, Marc N. Jarczok, Nicolas Rohleder, Graham A. Rook, Christopher A. Lowry, Harald Gündel, Christiane Waller, Stefan O. Reber. Less immune activation following social stress in rural vs. urban participants raised with regular or no animal contact, respectively. Proceedings of the National Academy of Sciences, 2018; 201719866 DOI: 1073/pnas.1719866115
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