New research reveals that children raised in a rural environment, surrounded by animals and bacteria-laden dust, grow up to have more stress-resilient immune systems and might be at lower risk of mental illness than pet-free city dwellers.

The study, co-written by integrative physiology professor Christopher Lowry, adds to mounting evidence supporting the “hygiene hypothesis,” which suggests that overly sterile environments can breed health problems. The findings also suggest that raising kids around pets might be good for mental health.

“It has already been well documented that exposure to pets and rural environments during development is beneficial in reducing risk of asthma and allergies later in life,” Lowry says. “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.”