The study, a joint effort between Brigham Young University and Shanghai Jiao Tong University in China, was conducted over a period of 16 weeks. In the first phase, researchers placed a group of eight-week-old mice, split evenly between male and female, on a high-fat diet. Once the 16 weeks were up, the second phase commenced, and all mice, including a group not on the diet, were put into stressful conditions for the following 18 days.
Throughout the course of the experiment, researchers collected samples of microbial DNA from fecal pellets before and after each stress test was conducted over the 18-day course. Once the analysis of the excrement was completed, researchers discovered differences in how male and female participants were affected by stress and anxiety.
"Stress can be harmful in a lot of ways, but this research is novel in that it ties stress to female-specific changes in the gut microbiota," Laura Bridgewater, the lead researcher, said in a statement. "We sometimes think of stress as a purely psychological phenomenon, but it causes distinct physical changes."
But it turns out that the most jaw-dropping find came from the group of female mice that weren't even on the specialized diet. Researchers noted that the gut microbiota — organisms that play a large role in digestive health — shifted in stressed female mice that weren't on the diet to appear as if they were. In other words, mice eating a normal diet, when put under stress, began to physically resemble their unhealthy counterparts.
"In society, women tend to have higher rates of depression and anxiety, which are linked to stress," Bridgewater added. "This study suggests that a possible source of the gender discrepancy may be the different ways gut microbiota responds to stress in males vs. females."
Though the study was limited mice, researchers also noted that their findings could translate to human beings.
In a separate study conducted by the American Psychological Association from August 2016 to January 2017, 80 percent of the participants had experienced at least one symptom of stress, such as headaches, feeling overwhelmed, depressed, nervous or anxious.