Node Smith, ND

A new study from the University of Colorado at Boulder shows that people raised in an urban environment without pets around have a less resilient immune system and may be at higher risk for mental illness.1 This research furthers the conversation of the “hygiene theory” into realm of mental health, connecting some of the factors known to affect mental health such as microflora, and immune function with growing up in an urban versus rural environment.

Over 50 percent of the world’s population now lives in cities

Because of this change, people are exposed to microorganisms at vastly different levels that in previous generations. This change in microorganism exposure, especially at younger ages may be influencing more than just gastrointestinal health, but immune function and psychological health as well.

Study furthers theory that overly sterile environments actually promote certain health problems due to lack of healthy microorganism exposure

The current study was conducted by researchers at both the University of Ulm in Germany and the University of Colorado at Boulder. It serves to further the theory that overly sterile environments actually promote certain health problems out of a lack of healthy microorganism exposure. The paper does correlate pets with having a beneficial impact as well on mental health.

Study looked at 40 German men (20 – 40 years of age)

The study looked at 40 German men (20 – 40 years of age). Half the group grew up on a farm with animals, while the other half were raised in a city and did not have any pets. The participants were put through a stressful scenario, which included giving a speech in front of a group, then asked to perform difficult math equations in a certain amount of time. Blood and saliva were analyzed 5 minutes before and after the stressful scenario was undergone, as well as at 15 minutes, 1 hour, 90 minutes and 2 hours post-scenario.

City group had much higher levels of peripheral blood mononuclear cells (PBMCs)

The city group had much higher levels of an immune cell line called peripheral blood mononuclear cells (PBMCs) after the stressor. IL-6, an inflammatory cytokine was also elevated, and anti-inflammatory cytokine, IL-10 was decreased.

Conclusion: individuals who grew up in city areas had a significantly higher level of inflammation in response to a stressor vs. those who grew up in rural environments

The conclusion of the study was that individuals who grew up in city areas had a significantly higher level of inflammation in response to a stressor, and it persisted for a longer period of time than those who grew up in rural environments. Interestingly, this group did not report feeling stressed, and in fact, the rural group reported feeling more stressed performing the tasks.

Results point out that there could be a significantly more dramatic response to stress occurring within this population which remains unknown

These results are interesting because they point out that there could be a significantly more dramatic response to stress occurring within this population that they don’t even know about. Other studies have suggested that individuals with a greater inflammatory response are more likely to develop PTSD and/or depression disorders later in life.

Microbial impact on immune function is shaped relatively early in life

Since research is fairly clear that microbial impact on immune function is shaped relatively early in life, the authors discuss the likelihood that growing up in a city versus a rural environment may impact these mental health concerns. Part of this may be the increased exposure to animals in individuals growing up in rural environments.

Source:

  1. Bobel TS, Hackl SB, Langgartner D, et al. Less immune activation following social stress in rural vs. urban participants raised with regular or no animal contact, respectively.PNAS. March 28 2018. doi:10.1073/pnas.1719866115

 

Photo by Matthew Hamilton on Unsplash


Node Smith, ND, is a naturopathic physician in Portland, OR and associate editor for NDNR. He has been instrumental in maintaining a firm connection to the philosophy and heritage of naturopathic medicine among the next generation of docs. He helped found the first multi-generational experiential retreat, which brings elders, alumni, and students together for a weekend camp-out where naturopathic medicine and medical philosophy are experienced in nature. Four years ago he helped found the non-profit, Association for Naturopathic ReVitalization (ANR), for which he serves as the board chairman. ANR has a mission to inspire health practitioners to embody the naturopathic principles through experiential education. Node also has a firm belief that the next era of naturopathic medicine will see a resurgence of in-patient facilities which use fasting, earthing, hydrotherapy and homeopathy to bring people back from chronic diseases of modern living; he is involved in numerous conversations and projects to bring about this vision.

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