A vicious cycle
The gut and the brain communicate back and forth via the vagus nerve, which runs from the brain to the large intestine. However, signals from the gut can also operate independently to influence and control our digestive tract – especially during times of stress.
And, people living with ongoing GI symptoms may actually be more susceptible to the effects of stress than the general population.
Environmental factors such as physical and emotional stress early in life also have potential impacts on how the gut’s nervous system (ENS) develops and on its lifelong physiological function. These factors can lead to GI dysfunction developing, even later in life.
Studies show that people with irritable bowel syndrome and Crohn’s disease have a reduced vagal tone, which may indicate a communication breakdown between the brain and the gut.(2) People with irritable bowel syndrome can misperceive the gut’s signals, causing emotional reactions that in turn increase GI symptoms, like urgency, bloating, nausea, and abdominal pain.
Gut-brain communication goes both ways. Stress signals in the brain that cause depression and anxiety can also trigger a response from the gut, resulting in GI discomfort. And, a distressed gut will send signals to the brain that cause emotional distress.
In other words, stress and digestive distress can become a vicious cycle.
Fight or flight vs. rest and digest
One example of how the brain and gut are connected is the “fight or flight” reaction. When we experience big emotional shifts such as fear, anxiety, or even excitement, a cascade response happens in the body. During a fight or flight reaction, you may feel heart rate and blood pressure increase while your breathing becomes faster and shallower.
Fight or flight mode, especially when chronic, disrupts normal gut-brain communication.
Because the body focuses on warding off a perceived threat, it conserves energy in other ways. For example, the gut’s nervous system (known as the enteric nervous system, or ENS) slows digestion in response to stress, resulting in abdominal discomfort, pain, and sometimes even feelings of urgency.
Over time, a heightened response to stress can cause:
- Worsening of GI symptoms, such as abdominal pain, bloating, and reflux
- Dysregulation of the GI tract, leading to difficulty swallowing, diarrhea, or constipation
- Visceral hypersensitivity, in which nerves in the gut are overly sensitive to gas, movement, and secretions
To counteract this natural stress response, we need to activate our body’s opposing system – the relaxation response via the parasympathetic nervous system, which is known as our “rest and digest” state.
We can begin to train the body to proactively activate this state, even in stressful situations.