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IBD Awareness Week: The Role of Stress, Part 2

Today I'm going to talk about the brain-gut connection and how it may play a role in IBD symptoms.  Yesterday I gave an overview of the HPA Axis, which recent research is implicating in the presence of inflammation and other changes in the digestive tract.  The brain-gut connection has some overlap to what I went over, so I'll try not to be repetitive.

Historically, the brain-gut connection has been connected with more "functional" conditions, such as Irritable Bowel Syndrome or Functional Dyspepsia.  Functional conditions are a class of disorders that are caused by problems with how the digestion system functions (see, medicine isn't all convoluted all the time), typically at the neurological or muscular level.

When a person with IBS has a colonoscopy, there is no evidence of inflammation either visibly or under the microscope when biopsies are taken and analyzed.  Their colon looks like that of a healthy person, even though they may have chronic abdominal pain, bloating, diarrhea, or constipation.

Isn't that pretty?
Don't let the lack of inflammation fool you. IBS is a very debilitating disease and costs billions of dollars every year in medical costs and lost productivity.  It affects between 25 and 45 million people in the US, can take on average 7 years to diagnose, and has limited medical treatments.  Many medications that have come to market for IBS have been pulled because of fatal side effects (e.g. Zelnorm, Lotronex).  Those that remain have about a 25-30% success rate, which isn't much better than placebo.

Remember these ads?  
So what is the prevailing theory behind IBS?  The brain-gut connection.  Although more recent studies are finding that there is some sort of inflammatory process in IBS, and some researchers are theorizing that IBS and IBD are related and lie on a continuum.  Others don't agree, and believe that IBS and IBD are distinct diseases that may overlap.  More on this later.

If you think about it, the brain-gut connection is part of our everyday language.  "Gut feelings." "Gut-wrenching." "Butterflies in my stomach."  Stress and emotions have a direct, and considerable, effect on our digestive system.  The gut has been called our second brain and is run by something called the enteric nervous system.  This system contains over 100 million neurons (more than are in your spinal cord or peripheral nervous system).  It also contains more of a chemical called serotonin than your brain (95% of it is in your gut, not your head).  You may have heard of serotonin as a chemical that's too low in people with depression.

Schematic of the BGC
Wired into the enteric nervous system is the autonomic nervous system, which I mentioned briefly yesterday. This system does a lot, but what's important for this post is that a sub-part of it (the sympathetic nervous system) drives the fight-or-flight response (aka, the stress response).  A lot of physical changes happen when we're perceiving a threat - our heart rate goes up, our breathing increases, blood is diverted to larger muscles (that's why cold hands and feet are a sign of chronic stress), we start sweating.  This system also tells the gut to stop digestion - because when you're about to get eaten by the saber tooth tiger, digesting your mammoth burger is a low priority.

Captain Caveman had to have had digestive problems.
I want to make clear that the fight-or-flight response isn't an all-or-nothing phenomenon.  Meaning, it's engaged whenever we experience stress.  Whether it's that irritating co-worker, an upcoming deadline, or almost being hit by a bus.  We don't have to feel the full effects of an adrenaline rush to know that the stress response is happening inside of us.  I often use the tachometer in your car as a way to think about this.  When your car is in neutral and you push on the gas pedal, the needle goes up.  You can do this gradually or you can stomp on the gas, sending it into the red.  The needle moves up and down according to how much pressure is on the pedal.  The same is true of the stress-response.

Who is Margret, and why are we always telling her to "punch it!"?
In conditions like IBS, the communication between the enteric nervous system and the brain is thrown off.  Unfortunately, researchers don't know why or how this happens.  Often times, the nerves in the gut become hypersensitive so people with a kooky (technical term) brain-gut interaction feel sensations in their bowels that they shouldn't, and are more likely to experience these sensations as painful.  Something called visceral hypersensitivity.

As I previously mentioned, there's some debate among gastroenterologists if a person with IBD can go on to develop IBS so they have both conditions.  Typically this idea is floated when an IBD patient comes to the doctor's office with symptoms but their bloodwork and colonoscopies are clear.  How frustrating, right?

At first I thought this was a silly idea, but as I thought about it and read the research, it makes some sense.  Chronic inflammation from IBD causes damage that you would think would affect the enteric nervous system, somehow.  Also, if stress has a direct effect on the functioning of the digestive system it would make sense that symptoms like diarrhea, pain, or bloating could be from this brain-gut connection and not an IBD flare.  It's tricky for patients and physicians to tease this out when the typical "red-flag" IBD symptoms aren't present.

I hope my 2 posts on stress and IBD have been informative.  For Part 3, I'd like to get reactions from people about these stress theories.  Do you agree?  Disagree?  What has your experience been with stress and your IBD symptoms?  It'll probably take me a few days to get feedback, so Part 3 will hopefully happen in the next week or so.

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