It has long been known that stress can wreak havoc with your digestive tract. Two new studies are proving that the sword cuts both directions. Problems in your digestive tract can wreak havoc in your brain, causing anxiety and depression.
Researchers have observed that around 15% – 20% of people struggle with recurring pain or discomfort in their upper abdominal area and these people are also more likely to be anxious or depressed. It is typical that their digestive problems were present in early childhood, prior to the onset of psychological struggles. These observations led Stanford University researchers1 to conduct an experiment to see if gut problems could be causing mood problems.
They exposed 10-day-old rats to mild inflammatory digestive injury, a time when gene settings relating to stress are taking hold, which may have an impact on the stability and health of the nervous system. The digestive inflammation healed, and then the rats behavior was followed as they grew older compared to a control group. By weeks 8 – 10 the rats had developed anxiety and depression. They had higher levels of stress hormones as a baseline and an exaggerated response when exposed to stress.
“The gut and the brain are hardwired together by the vagus nerve, which runs from the brain to the body’s internal organs” said Pankaj Pasricha, MD, professor and chief of gastroenterology and hepatology at Stanford University School of Medicine. “In addition, the gut has its own nervous system that is relatively independent. So the communication between the gut and the adult brain is elaborate and bi-directional, and changes in the gut are signaled directly to the brain. It seems that when the rats are exposed to gastric irritation at the appropriate point in time there is signaling across the gut to the brain that permanently alters its function.”
In a second study researchers at McMaster University in Canada2 used mice to show that administration of antibiotics altered the behavior of the mice, resulting in anxiety and changes in brain chemistry that could lead to depression. When the antibiotics were discontinued the behavior returned to normal (many humans may not be so fortunate). They next conducted experiments with germ-free mice by exposing them to the gut bacteria of other mice with specific behaviors. When the germ-free mice were colonized with the gut bacteria of active and daring mice they took on those traits. When they were colonized with bacteria from passive mice they become passive.
The researchers were quite excited about their work. They believe that these results lay the foundation for investigating the therapeutic potential of probiotic bacteria (friendly flora) in the treatment of behavioral disorders, particularly those associated with gastrointestinal conditions such as irritable bowel syndrome.
In my recent article How Digestive Problems Prevent Weight Loss I explore other aspects of this issue as it relates to metabolism. It is quite interesting that the hunger hormone ghrelin is associated with digestive inflammation. In fact, ghrelin release acts as a primary anti-inflammatory to the vagus nerve. This indicates that craving behaviors for food in particular, and possibly many other substances, have an overheated vagus nerve as part of the problem. Because the overheated vagus nerve could be coming from bacterial imbalance or infection with subclinical amounts of E. coli, salmonella, or staphylococcus it is now becoming clear that gut problems may pose huge issues for brain function.
Decades of reckless antibiotic use by the medical profession, has clearly caused ongoing digestive misery for millions of Americans. It can now be hypothesized that it has caused millions a fair amount of emotional trauma as well. The new science says that it is more than a gut feeling.
- ^ Early Life Digestive Distress May Promote Later Life Depression and Anxiety PLoS ONE Liansheng Liu, Qian Li, Robert Sapolsky, Min Liao, Kshama Mehta, Aditi Bhargava, Pankaj J. Pasricha.
- ^ Antibiotics Alter Behavior Via Bacterial Imbalance in the Gut Gastroenterology Emmanuel Denou, Wendy Jackson, Jun Lu, Patricia Blennerhassett, Kathy McCoy, Elena F. Verdu, Stephen M. Collins, Premysl Bercik.