Post-Traumatic Stress and Digestion: What’s the Connection?

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Is there a connection between post-traumatic stress and digestion? Can PTSD cause digestive problems? To answer these questions, let’s look at the nervous system and how it operates, the symptoms of Post Traumatic Stress Disorder (PTSD), and how digestion works. Read on to learn more, and to find out how the healing process takes place.

The Vagus Nerve and Nervous System Arousal

There are two main states of nervous system arousal: 1) parasympathetic and 2) sympathetic. Parasympathetic nervous system arousal is responsible for “rest and digest.” Sympathetic nervous system arousal is responsible for “fight or flight.” The field of neuroscience has shown that nervous system arousal is regulated by the vagus nerve, also called the Xth cranial nerve.

The vagus nerve is basically the parasympathetic nervous system. It innervates the face, heart, and gut, and under stress-free conditions, it keeps us relaxed but alert. It helps our face relax when we see another friendly face. It keeps our heartbeat within a resting rate and keeps our gut working to digest.

However, when our brain’s alarm system, the amygdala, recognizes the danger, muscular tension clamps down on the vagus nerve, and changes occur in the face, heart, and gut. Pupils dilate to see more movement, and their ears perk up to hear even the subtlest sounds. The heartbeat increases to pump blood into our limbs for faster flight or stronger flight.

Blood pumps out of our gut to bias our energy toward movement and away from digestive processes. We may even involuntarily eliminate waste or urine in an attempt to get rid of anything that will slow us down.

When we experience an event that we can neither fight nor flee from, our nervous system kicks into a dual arousal of both sympathetic and parasympathetic nervous system arousal for a freeze response. We simultaneously feel like we are going to die if we move or don’t move. This is where trauma happens. If we cannot process the movements and arousal through our nervous systems, the trauma becomes PTSD.

Post-Traumatic Stress Disorder and Trauma: Five Factors

According to the DSM, there are five major factors that indicate someone is suffering from Post Traumatic Stress Disorder: Stressor, Intrusion symptoms, Avoidance, Negative alterations in mood and cognition, and alterations in arousal and reactivity.


The stressor occurred when the person was exposed to one of the following: death, threatened death, actual or threatened serious injury, or actual or threatened sexual violence. This stressor was either through direct exposure, witnessing the event happening to someone else, or indirectly through hearing about it from a 3rd party source. It can also happen from repeated indirect exposure for first responders to trauma, such as medical and health professionals, and may be referred to as compassion fatigue.

Intrusion symptoms

Intrusion symptoms occur when the traumatic event is consistently re-experienced in one of the following ways: 1) recurrent, involuntary, and intrusive memories, 2) traumatic nightmares, 3) dissociation reactions such as flashbacks, 4) intense or prolonged distress after exposure to traumatic reminders, and 5) marked physiologic reactivity after exposure to trauma-related stimuli.


Avoidance involves avoiding either internal thoughts and feelings related to the traumatic event, or external stimuli that remind the person of the trauma. These can include people, places, activities, or times of the year.

Negative alterations in mood and cognition

When examining negative alterations in mood and cognitions, two of the following seven are present in cases of PTSD: 1) the inability to recall key features of the event (not due to other factors such as head injury or substances), 2) persistent and distorted negative beliefs and expectations about oneself and the world, 3) persistent distorted blame of self or others for causing the trauma, 4) persistent trauma-related emotions such as terror, horror, anger, guilt or shame, 5) markedly diminished interest in pre-traumatic significant activities, 6) feeling alienated from others, and 7) persistent inability to experience positive emotions.

Alterations in arousal and reactivity

In negative alterations in arousal and reactivity, people dealing with PTSD will exhibit two of the following six symptoms: 1) irritable or aggressive behavior, 2) self-destructive or reckless behavior, 3) hypervigilance, 4) exaggerated startle response, 5) problems in concentration, and 6) sleep disturbance.

Post Traumatic Stress and Digestion

So how are post-traumatic stress and digestion related, and what are PTSD digestive problems? When we have unresolved trauma from abuse of any kind, war, or natural disaster, our nervous systems stay in a chronic state of sympathetic nervous system arousal. In sympathetic nervous system arousal, we are hypervigilant and the blood stays in our limbs rather than our bellies for digestion.

Our bodies emotionally and physiologically haven’t gotten the memo that we’ve survived the traumatic events, and are still responding as though they were in the trauma. When our bodies are under post-traumatic stress, they respond to anything as a threat, including food. When we eat under stress, we interrupt all the phases of digestion.

There are four main phases of digestion: 1) cephalic, or head, 2) esophageal, 3) gastric, and 4) intestinal.

The cephalic phase of digestion is the preparation phase. We get our minds in a state of relaxation and readiness for our bodies to digest with saliva and enzymes. When we are hypervigilant, this phase is bypassed almost entirely. We remain in an activated, sympathetic state.

The second phase, esophageal, is affected by PTSD because we are not chewing well. Our bodies are biased toward speed. We aren’t present with our food. Our throat may be tightened as part of our sympathetic arousal. This happens in trauma as a way to clamp down on any noises we may make that could give us away from the threat. Salivary and mucous productions are inhibited, making swallowing harder. This also affects the gastric phase.

The third or gastric phase is where our stomach acids break down food into a paste called chyme, making the nutrients ready for absorption. When stomach acid is too low because the body is in a chronic state of sympathetic nervous system arousal, the chyme will sit in the stomach until the pH balance is right for moving it to the small intestines. This affects transit time for digestion and causes food to sit in the stomach longer. It also interferes with the breakdown of proteins and allows for the growth of harmful bacteria.

When our smooth muscle is hypertonic (tight) or hypotonic (limp) from chronic states of sympathetic activation, it can disrupt the functioning of our pyloric and lower esophageal sphincters. These are the doorways to our stomachs from the lower and upper portions, respectively. We can experience heartburn from stomach acids escaping a weakened lower esophageal sphincter and dumping syndrome from a weakened pyloric sphincter.

By the time the food enters our intestines for absorption in the fourth phase of digestion, our livers are busy trying to filter the higher levels of cortisol flowing in our systems, slowing our blood filtration and immunity. This affects our intestinal ability to absorb nutrients into our bloodstream.

Because the macronutrients may not break down into small enough chains for our bodies to readily absorb, they may enter our bloodstream and appear to be foreign invaders to our immune systems. Food sensitivities may then develop, taxing our digestive systems even more. When our guts are not eliminated properly and are full of harmful bacteria, it increases mood disorders such as anxiety and depression.

There is a parallel process happening in our gut that mirrors the avoidance symptoms of PTSD. There is a “gut brain” that contains 90% of the neurotransmitters found in the head. As post-traumatic stress causes avoidance of painful internal or external stimuli in our conscious lives, our guts avoid stimuli that look like threats in our unconscious lives.

Most health conditions can be linked to or supported by digestive function. All sorts of autoimmune disorders, such as Irritable Bowel Syndrome, Celiac disease, and thyroid conditions are affected by gut health. Post Traumatic Stress Disorder can also affect weight gain. Mood disorders such as anxiety and depression can also be a product of an unhealthy gut microbiome. That is how trauma causes stomach issues.

How to Manage PTSD and Stomach Pain?

As we discuss in the Institute for the Psychology of Eating’s approach to personal transformation, Dynamic Eating Psychology, one of the most important ways to support health is to get the gut functioning properly.

In addition to probiotics and enzymes, learning to mindfully bring yourself out of sympathetic nervous system arousal and into parasympathetic is the most effective way to reverse the negative effects of PTSD and improve digestion.

If you would like more information on how to work with post-traumatic stress and digestion, please see our blog on Resourcing: The Antidote for PTSD. I hope this is helpful!

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