University of Colorado Boulder researchers believe their findings prove that kids need to be out in nature more, as environments too sterile can have an impact on mental health.
Human are become less exposed to microorganisms as close to 50% of the globe's population living in area.
"It has already been very well documented that exposure to pets and rural environments during development is beneficial in terms of reducing risk of asthma and allergies later in life," author of the study Christopher Lowry, a professor of integrative physiology at CU Boulder, told Daily Mail. Adding, "This study moves the conversation forward by showing for the first time in humans that these same exposures are likely to be important for mental health."
40 German men between the ages of 20 to 40 years old participated in the study. 20 were raised on farm, while the rest were city folk.
The participants had to give a speech in front of people who showed no reaction to test their stress levels. They also had to solve math equation and given a certain amount of time.
The men also provided blood and saliva samples so researchers could monitor their immune response. Those results proved to be very insightful. Levels of peripheral blood mononuclear cells (PBMCs) were much higher in men who were raised in cities.
"People who grew up in an urban environment had a much-exaggerated induction of the inflammatory immune response to the stressor, and it persisted throughout the two-hour period," Professor Lowry explained in the report.
He added: "If you are not exposed to these types of organisms, then your immune system doesn't develop a balance between inflammatory and anti-inflammatory forces, and you can develop a chronic, low-grade inflammation and exaggerated immune reactivity that makes you vulnerable to allergy, autoimmune disease and, we propose, psychiatric disorders."