A Traumatic Experience Can Reshape Your Microbiome

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I’m not disputing the scientific soundness of the whole brain-gut connection, but it really does sound a little bit like something out of a science-fiction story. I mean, you’re telling me that the trillions of tiny organisms that live in my gut, chomping up my food for me and maintaining my digestive system, have an impact on what I think and do and say? That the content of my thoughts might be at least partially determined by the eggs I had for breakfast, or the vitamin C I haven’t consumed enough of? It boggles the mind (at least, a mind influenced by my microbiome, fueled almost exclusively by Sour Patch Kids).

Strange as it may seem, though, it’s also a case of our science finally catching up to our idioms. Without realizing it, we’ve been talking about the link between brain and gut for a long time: Ever had a gut-wrenching car ride, or a gut instinct about someone, or butterflies in your stomach? In less colorful terms, the stomach and the mind really do talk to one another; in one study, for example, tentative mice that received gut bacteria transplants from braver ones became more fearless, exploring a maze with less hesitation. So strong is the microbiome’s impact that some have deemed it the “second brain.” And recently, a team of researchers found that our guts may harbor evidence of difficult life experiences many years after the fact, changing everything from how we digest food to how we process stress. In fact, these changes in our “second brain” may substantially alter the structure of our first, creating a feedback loop between the two.

For the study, published last month in the journal Microbiome, the authors analyzed the microbiomes of a group of students with irritable bowel syndrome, or IBS, a fairly common chronic condition marked by pain in the stomach, gas, and indigestion. (Though there are ways to manage IBS, many of which involve reducing stress, we don’t know what causes the syndrome.) They did the same for a control group of healthy volunteers, and also collected brain scans, stool samples, and behavioral and biographical information from participants in both categories.

The results were startling: Across the board, those in the IBS group were far more likely to exhibit anxiety and depression. When the researchers further divided IBS-afflicted subjects into two smaller groups — those with a microbiome undistinguishable from that of a healthy control, and those with noticeable differences — they found that the subgroup with different microbiomes also had more history of early life trauma, and their IBS symptoms lasted longer. “It is possible,” the authors wrote, “that the signals the gut and its microbes get from the brain of an individual with a history of childhood trauma may lead to lifelong changes in the gut microbiome.”

It’s also possible — or even probable — that the relationship isn’t uni-directional. The researchers noticed that the people with altered microbiomes had differently shaped brains, too, suggesting that the impacted gut may have doubled back and impacted certain brain regions — though they noted in the study that they don’t have enough information to be sure that’s the case, and cautioned against leaping to conclusions. Even more than the science of the gut on its own, the science of what how it affects the brain is still in its infancy; rather than arriving at any firm conclusions, this study is meant to open up the field more, laying a foundation for future researchers to build on.

If it’s true that the gut influences the brain just as the brain impacts the gut, though, then these findings may have tremendous implications for both mental and physical health. It might be a stretch to say that anxiety meds could one day be supplemented with kombucha, but it’s not too wild to imagine a future where treating ailments of the mind also involves treating the digestive system, or vice versa (already, some people are using talk therapy to ease IBS). For now, it can’t hurt to remember the connection between the two, and do everything in your power to live a life that gives you peace of mind — because it’ll give you peace of stomach, too.

A Traumatic Experience Can Reshape Your Microbiome