The Brain-Gut Connection: A Connection to Consider When Experiencing any Mood Disorder
The brain and the gastrointestinal tract (the gut) are much closer friends than we once thought.
Symptoms of anxiety and depression and symptoms of poor gut-health often co-exist. Why is that?
If you are part of the 30-40% of the population who has suffered from a functional bowel disorder, you may know that mood symptoms often accompany the uncomfortable gastrointestinal symptoms.
Depression and anxiety are known to be closely tied to disorders of the gut, and for a long time, it wasn’t clear why. We now know that the communication between the brain and the gut is a two-way street. And it’s no country road. It’s more like an 8-lane highway.
Anxiety and mood disorders (such as depression) have been shown to exacerbate symptoms of gastrointestinal distress such as bloating, constipation, diarrhea, and stomach pain. However, gastrointestinal irritation can also alter your mood. And it isn’t as simple as feeling frustrated by your symptoms.
The enteric nervous system
You may have heard of the pathway known as the microbiome-gut-brain axis. This axis describes the flow of information between the big brain in our heads and the “second brain” in our guts. This second brain is the enteric nervous system (ENS), the gut’s own robust communication system. This ENS communicates the state of our guts to our brains while also listening to communication from the brain. In fact, most information moves from the gut to the brain, not the other way around.
The enteric nervous system functions separately from the central nervous system (which consists of the brain and spinal cord) but is in constant communication with it. The ENS lines the entire gastrointestinal tract from the esophagus to the rectum and is responsible for managing the complex process of digestion. We now know that it is also partly responsible for regulating our moods.
To understand how the ENS regulates mood, we need to look to the microbiome – the new (but not new) mental health superstar.
The gut microbiome refers to all the microscopic organisms that live in our guts. There are a staggering number of microorganisms that call our bodies home. In fact, there are at least as many bacterial and other microbial cells in the human body as there are human cells. Most of these microorganisms are beneficial to us - we can add these tiny helpers to our gratitude lists. The gut microbiome, in particular, is immensely important to our well-being. These bacteria live in harmony with us, helping us digest our food, producing vitamins, and helping our immune systems function properly.
Though the benefits of a healthy microbiome for digestion are well known, until recently, we didn’t know just how important the microbiome is for mental health. Recent research has found that the microbiome and the enteric nervous system, the gut’s surprisingly sophisticated communication system, establish a relationship with one another and begin to mature as soon as we are born. These two grow up together. We get our first dose of microbes from our mothers at birth and we are born with immature enteric nervous systems. There is now evidence that the microbiome actually regulates the development of the enteric nervous system. An unhealthy microbiome does not allow the enteric nervous system to develop properly. However, when healthy gut bacteria are introduced into the gut, the enteric nervous system begins to function normally again.
The Brain-Gut Connection
A healthy microbiome then is vitally important for a fully functioning enteric nervous system (which positively impacts mood). A healthy microbiome, in addition to helping us digest food, restricts the growth of harmful bacteria, just as a healthy lawn restricts the growth of weeds. When the healthy bacteria are waning because their environment is not hospitable, harmful bacteria have a chance to take over. When the lawn dies away, the weeds take over. Studies have shown that depression is associated with a lack of diversity and richness of microorganisms in the gut. A healthy microbiome is diverse. When harmful bacteria are proliferating, the diversity in the gut plummets. It has been hypothesized that chronic dysbiosis, an imbalance of bacteria in the gut, can reduce serotonin levels, a neurotransmitter that positively impacts mood. Low serotonin often leads to depression. A popular class of anti-depressant medications, in fact, is selective serotonin reuptake inhibitors (SSRIs) which can alleviate depression by making serotonin more available to the brain. At least 90% of serotonin is produced in the gut. When the gut is unable to produce serotonin, mood is affected. This is one of the reasons why mood and anxiety disorders are so deeply intertwined with functional bowel disorders.
So why does the microbiome get out of sorts?
Chronic stress
A diet that lacks sufficient nutrition
Use of antibiotics
Low fiber intake
Lack of physical movement
Let’s look at a couple of these in more detail.
Stress
Chronic stress is harmful. Psychological stress can reduce both the abundance and the diversity of our gut microbes. This depletion of the microbiome cripples the gut which can then lead to worsening symptoms of anxiety or depression. If you’ve found yourself in this cycle, know that there is help. When stress has kick-started gut dysfunction, therapy can help get both the gut and brain back on track.
Diet
The microbes in our guts are quite sensitive to dietary changes. Whole plant foods keep the microbes happy by nourishing both us and them. A diet heavy in meat, dairy products, or processed food does not provide sufficient nourishment to the microbes we need and they begin to die off. Fiber is another important piece of the puzzle. You probably know that you should eat plenty of fiber, but you might not know why. The microbes we want in our guts feed off fiber (which is readily found in whole plant foods). Plant foods high in fiber support a healthy and diverse microbiome which in turn boosts our immune systems and reduces inflammation in the body. Chronic inflammation is associated with depression as well as many chronic physical illnesses.
Note: I’m all for variety and balance in a diet. The way you decide to eat is unique to you. Practice releasing any judgment you may have for the way you eat and get curious about how your diet may be affecting your gut health and your mental health.
What changes can you make?
Schedule an appointment with a therapist to help you manage any psychological symptoms you are experiencing. Remember that therapy is not just for people with severe mental illness. Therapy is for anyone who could use some assistance working through the challenges of life. Gut dysfunction is a challenge with strong links to mental health. Caring for your mental health is a critical step to take for your overall health.
Reset Brain and Body offers integrative mental health care that supports your brain…and your body.
Notice how what you eat affects your mental health and your physical symptoms. Bring awareness to the patterns you see in your gut symptoms, how you’re eating, and how you’re feeling mentally. Speak with a dietician to help you best nourish your body and your mind.
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