By Leah Harris

Could Your Gut Influence Fear Responses in PTSD? New Study Suggests the ‘Gut-Brain Axis’ May Provide Clues for Trauma Recovery

For many years, mental disorders were simplistically understood as imbalances or deficits in the neurotransmitters in the brain. Recent research has debunked the “chemical imbalance” theory, and has given rise to more complex understandings around how the various systems of the body interact to influence physical and mental health. For example, many people are unaware that 95% of the “feel-good” neurotransmitter serotonin in the body is produced in the intestinal tract.

In recent years, scientists have begun to study what is known as the “gut-brain axis,” or the system of communication between the brain and the gut. Scientists have discovered what could be called “a second brain,” located in the walls of the digestive system. This “second brain” is referred to in scientific literature as the enteric nervous system (ENS), made up of two thin layers of more than 100 million nerve cells that line the gastrointestinal tract from esophagus to rectum. Increasingly, science is coming to understand that the ENS interacts in complex and significant ways with the central nervous system (CNS) via the vagus nerve and what is known as the “adaptive immune system.” 

The recognition of the complex and delicate interactions between different systems in the body has given rise to a new field called “psychoneuroimmunology.” 

A new study published in the journal Nature has found that a community of microbes that live in the gut – known as our microbiome – can make it harder to overcome conditioned responses to fear that are characteristic of Post-Traumatic Stress Disorder (PTSD). In the study, mice whose microbiomes were altered by the introduction of antibiotics, continued to show elevated fear responses, even when the initial threat was no longer present. 

This study is particularly significant, because it marks the first time scientists have been able to show a reduction in what is known as “fear extinction” – or the ability to forget a learned response to a fearful situation – based on changes in the gut that may result from the introduction of antibiotics, stress, and diet. One of the study’s authors, Professor David Artis, told The Independent: “It has implications for our understanding of how diet, infection and lifestyle influence brain health and subsequent susceptibility to neuro-psychiatric disorders.”

“The gut-brain axis impacts every single human being, every day of their lives,” Dr. Artis told Science Daily. “We are beginning to understand more about how the gut influences diseases as diverse as autism, Parkinson’s disease, post-traumatic stress disorder and depression. Our study provides a new piece of understanding of how the mechanisms operate.”

Scientific understandings of the gut-brain axis hold promise not just for the alleviation of troubling symptoms of PTSD, but also add to our understanding of how common digestive disorders, such as Irritable Bowel Syndrome (IBS) can influence mental health.

While science has much more to learn about these complex gut-brain interactions and how they influence trauma recovery, there are steps you can take right now to improve your gut health. These include introducing more fermented foods into your diet, which can help to restore healthy gut flora, reducing the consumption of inflammatory foods like processed sugar and dairy products, and avoiding unnecessary or excessive use of antibiotics. 

If you must take antibiotics, you can balance out your gut bacteria by taking a probiotic supplement. According to an article in the Harvard Health Blog, “Studies have shown that when people take probiotics (supplements containing the good bacteria), their anxiety levels, perception of stress, and mental outlook improve, compared with people who did not take probiotics.”

To learn more about the gut-brain axis, see: