The Brain and the Gut

Mar 5, 2017 by

You can have me read this article to you instead of reading it yourself…

Or you can read it the old-fashioned way below…

At this point we have built a great general understanding for the GI tract and its inhabitants.  But in order to get a good, 360-degree view of our gastrointestinal system, we have to look at another organ entirely – the brain.

The Human Brain and Nervous System

The human brain is a powerful thing. It is the most complex brain known to exist on this planet, and  it is the most complex organ in the human body.  Without it, the body ceases to function. It contains around 86 billion neurons (nerve cells) and trillions of synapses (brain cell connections).

The human nervous system is split into two separate components. The brain is part of what is called the Central Nervous System (CNS), which basically acts as the command center for the body. The CNS also includes the spinal cord and the retina, which is part of the eye.

The rest of the nervous system, which connects all of the nerves in the body back to the spinal cord and brain, is called the Peripheral Nervous System (PNS). This expands out into your hands and arms, feet and legs.

There is another way that the human nervous system is divided up – functionally. This means that the human nervous system actually works in two very different ways in the body.


The somatic functions are the ones that we most often associate with the nervous system – coordinating all of our senses and movements. As I type this paragraph, my brain is instructing my somatic nervous system to move my fingers across the keys.  And as my fingers are touching the keys that they are pressing, my somatic nervous system is sending a signal to my brain where it will be interpreted into a feeling.


This is the oft forgotten portion of the nervous system.  It is responsible for all of the things that our bodies do that we don’t have to think about, such as breathing and regulating blood pressure.  It is also responsible for a function of the GI tract that we have already discussed – stimulating peristalsis.

These are referred to as involuntary movements, because they are done without conscious thought.  As you can imagine, the GI tract must belong to the autonomic nervous system, because we do not consciously will our GI tracts to function.  But it gets even more specific from there.

The Second Brain

The autonomic nervous system has a subdivision below it that is called the enteric nervous system. As you would expect for a part of the autonomic system, it also controls involuntary movements.  However, this part of the nervous system is specifically dedicated to the gastrointestinal system.

This is the highly specialized portion of the nervous system that is responsible for those coordinated muscle contractions that create peristalsis.  In fact, it is so complex, it contains the same number of neurons as the spinal cord.  It can even conduct its function completely alone, without any input from the brain!

The enteric nervous system has earned the special distinction of being called the Second Brain. This is due to its complexity and the large number of neurons that it contains.  It was not until recently that research started to unravel some of the additional functions that this second brain may actually be involved in.

When Two Brains Talk

One of the most interesting things about the enteric nervous system is that even though it can function on its own, it still communicates regularly with the central nervous system and the brain.  This is done to add more functionality and make the gut a team player with the rest of the body.

For instance, the brain can have a say in how quickly or slowly the food moves through the GI tract. It can also translate the sight of certain foods into preparatory secretion of specific chemicals in the stomach and intestine. There is a lot more that the brain can do in relation to the enteric nervous system, but for the sake of relevance, we’ll stop there.

The complexity of this nervous system is far outside of the scope of this article, so I won’t waste any time trying to explain it in great detail.  Instead we’ll take this information and move right along into why this is important to someone with a chronic GI condition (because it really, really is!).

From this point on, I’m going to do us a favor and simply refer to “the gut” – the combination of the enteric nervous system and the GI tract.

Brain-Gut Axis

The brain and the gut have what we now understand to be two-way communication. That means that the brain can have an influence on what is happening in the gut and the gut can have an influence on what is happening in the brain.  This communication stream has been referred to as the brain-gut axis.

In fact, this axis has actually been demonstrated to connect the emotional centers of the brain with the GI system.  This has some very clear implications to anyone that has or has had a GI condition. Have you ever noticed that stress triggers a worsening of symptoms?  That challenges in life seem to compound on each other by adding challenges from your gut as well? Or that focusing on your symptoms negatively affects your mood and psyche?

It turns out that this is not in your head and that there is a very real correlation between what your brain is experiencing in the rest of your life and what your GI tract is experiencing from your chronic condition. We will get into more discussion about this connection in just a bit.

The Brain, The Gut, and…Bacteria?

A very interesting and somewhat unexpected discovery in recent years is how important our gut bacteria might be to this communication axis. As we discussed previously, there are thousands of bacterial species in the gut, each with their own unique function and role that we, for the most part, have yet to fully understand.  Recent research has indicated that these same bacteria are also responsible for sending signals to the enteric nervous system regarding their responses to medications and foods in the GI tract.

This is one of those evolving fields of science where we don’t have very much confirmed information yet.  Validating the early discoveries and what we think we know in this field will take years.  So for now we have to be skeptical and hesitant regarding any sensational news releases until more information is available.

Your GI Diagnosis: The Chicken or the Egg?

We have established that there is an undeniable two-way connection between our brains and our guts that goes so far as to actually impact our emotions and moods. But do we know if one of those connections is stronger? Or if we can tell which one is pushing harder at any given time and overriding the other? Is our gut bringing us down, or are we actually making our symptoms worse?

When an undesirable mental state occurs for those with a chronic GI condition, it may be viewed differently depending on what life was like prior to the diagnosis. For instance, people that considered their lives generally happy and balanced prior to developing symptoms may blame the GI condition for any current depression or anxiety.  This is a reasonable conclusion, considering the social isolation and sudden changes in lifestyle that often come with GI conditions.

Studies even exist showing that depression and anxiety occur often in those with GI conditions, and that this can go in both directions.  For those that dealt with depression or anxiety prior to the development of gastroparesis symptoms, they might note that their mental state remains the same. Or they may see a very real connection between their GI symptom severity and their mental state as it changes.

There is evidence to support the idea that those with depression or anxiety may be more likely to develop certain GI conditions. And it is very accepted that certain psychiatric medications are capable of treating some GI disorders and symptoms, although we are still learning which ones to use, and when.

What Does the Research Say?

The accurate explanation for any situation will depend completely on the personal factors involved, and will be different for each person. Let’s take a look at some of the studies that confirm that these considerations truly do exist.


One of the largest and most valid studies that has been conducted on this topic evaluated people with IBS, GERD and IBD. In this study, they sent out a survey that asked questions about mood and psychological state to a random group of people. Of the 1,000 people that responded, 376 had one of these GI conditions.

Twelve years later, they sent out the same survey again. At that time, some GI conditions had resolved, but others had developed a GI condition, leaving the total number of people with GI conditions about the same.

Let’s take a look at what they found:

  • A high level of anxiety at baseline led to a higher chance of developing IBD.  A higher level of depression at baseline led to a higher chance of developing GERD.
  • Developing these GI conditions increased the chance that someone could develop anxiety or depression.


A different study looked specifically at people with gastroparesis.  This one was a little bit different, and not as robust (there weren’t as many participants).  In this study, depression and anxiety surveys were obtained from 300 people with gastroparesis.  These surveys were correlated with questions related to the severity of gastroparesis symptoms.

And in this study they found:

  • Depression and anxiety did appear to worsen as the severity of the gastroparesis increased. Specifically, the worsened symptoms included nausea, vomiting, bloating, and feeling full after eating.
  • This indicates that the severity of the psychological condition worsened alongside the severity of certain gastroparesis symptoms.  This was not associated with the rate of gastric emptying or with what caused the gastroparesis in the first place.

What Does it Mean?

The two studies we have already looked at provide interesting points for contemplation.  It does appear that GI conditions and psychological conditions can have an impact on each other. It appears that the GI condition may be the chicken or the egg, depending on the specific situation, and that the messages can go in either direction at different times.

There are a number of additional studies that have looked at various GI conditions and established a correlation between psychological state and GI disease severity.  There are also some other conversations that have been ongoing regarding the consideration of psychological state in the treatment of gastroparesis and other GI conditions.  For the sake of brevity, I won’t discuss these very similar findings here, but the links are available if you are interested in reading more.

It is also important to recognize that the correlation between these two factors actually provides a huge opportunity for us to make an impact on our own situations.  We might not have control over the involuntary movement of the second brain in our guts, but we do have some ability to reign in the primary one in our heads.

Putting it Into Action

It is crucial to realize the psychological impact that a GI diagnosis and the symptoms that come with it can have on every person.  It is also important to recognize that anxiety, depression, and negative thoughts can actually worsen symptoms even more.  It is a vicious cycle that is all too easy to get caught up in.

While it may sound endlessly cheesy to say, the importance of positivity cannot be stated enough.  And I can say from my own experience that distractions and staying busy are almost as important as a positive perspective.  Seeing a counselor, learning coping strategies, and being open to treatments that you may need to keep your psychological symptoms under control – these are just as important as getting a handle on your GI symptoms.

Whether we like it or not, our brains and our guts go hand-in-hand – a lesson that I wish I had learned much earlier on.  Harnessing the leverage that comes with this understanding can be the game-changer that sets you on your path to better health!



Refer back to the GI Tract Info Hub for more information on the GI tract.

Or learn all about chronic GI diagnoses, like IBD, gastroparesis, and IBS.

Related Posts


Share This

Share This