Gut Problems Can Cause Anxiety: Role of the Gut-Brain Axis

Anxiety is complex with many causes, none of which are personal flaws or weaknesses. In fact, researchers have discovered and are working to understand yet another reason anxiety is not your fault. Anxiety (depression, too, actually) is well-known as a mental health experience. It turns out that anxiety and depression are very much physical health conditions, too. As scientists learn more about the gut-brain axis, the more they understand that problems in the gut can cause anxiety and depression.^1,2 

What Is the Gut-Brain Axis?

People used to understand the brain as a sophisticated organ that controlled the rest of the body and was the only part of us involved in thoughts and emotions. The digestive system, or the gut, was understood as a collection of things like organs and glands that digested our food. When the brain needed fuel, it told the gut to feel hungry. That was once thought to be the extent of the interaction between brain and gut. 

Our knowledge is ever-changing, though, and we're beginning to know how very limited and wrong this original understanding was. The brain and the gut are each highly complex, and together, they are both directly responsible for how we interpret and react to our experiences and how we feel both mentally and physically. The highly sophisticated connection between the gut and the brain is known as the gut-brain axis, and it has an important role in our mental health. 

The gut has its own nervous system (called the enteric nervous system [ENS]), and while it doesn't think the way the brain does, our gut and ENS have nonetheless been dubbed our "second brain."³ The ENS is independent yet intricately connected to the central nervous system (CNS). It produces hormones, neurotransmitters (including the well-known mood neurotransmitter serotonin), and substances connected to the immune system. 

The gut also has its own living ecosystem of numerous species of microorganisms, including many types of bacteria and yeast. This system is the gut microbiota, and it influences our physical and mental health and overall functioning. 

The gut and brain constantly (as in every second of our lives) send messages back and forth along the gut-brain superhighway. The gut-brain axis is largely responsible for how we feel, including our moods and our stress levels. 

What Does the Gut-Brain Axis Have to Do with Anxiety and Depression? 

The gut-brain axis has a great deal to do with our mental health, including anxiety and depression. While researchers are still studying this complex system and how it impacts us on every level, it is now widely accepted that stress and emotions cause problems in the gut, and, separately, problems in the gut can cause mental health disorders.

A few things we know when it comes to the gut, anxiety, and depression:

• Gut dysbiosis can cause anxiety and depression. Gut dysbiosis is a disruption in the balance of the microbiota. This change, this imbalance, can happen because of stress, diet, and/or medications. Changes in this living system impact every cell in the body and brain and are directly linked to mental illness (not just anxiety and depression, but schizophrenia and neurodevelopmental conditions like autism, too). 
• Inflammation in the gut can cause anxiety and depression. An inflamed gut releases cytokines and neurotransmitters into our total system. Cytokines are a variety of substances secreted by immune system cells (which are part of the enteric nervous system) that affect other cells in the body. Elevated levels of some cytokines are associated with a compromised blood-brain barrier. As unwanted substances "leak" into the brain, problems like anxiety, depression, and memory loss can develop. Cytokines can also stimulate our stress reaction, causing the hypothalamic-pituitary-adrenal axis to activate and, among other things, flood the body with stress hormones like cortisol. This negatively affects mental health.
• Stress and emotions affect both the brain and the gut. Distress and emotions are experienced by both the brain and the gut. When one is under any type of stress, it signals the other to react. Whether anxiety and stress originate in the brain or the gut, both "brains" are impacted. The result is often a loop of distress between the CNS and ENS that causes, perpetuates, and intensifies anxiety, depression, and other challenges. 

The relationship is so complex that it can be hard to tease out which comes first. Does emotional stress aggravate the gut, or do problems in the gut aggravate the brain, mood, and mental health? At this point in our understanding, it seems like it can be both. Mental health is also gut health, and vice versa.

Therefore, it is important to care for your entire self, your whole body-mind together. To manage and treat anxiety, then, tend to your gut as much as your mind. 

Sources

1. Clapp, M. et al., "Gut Microbiota's Effect on Mental Health: The Gut-Brain Axis." Clinics and Practice, September 2017. 
2. Harvard Medical School, "The Gut-Brain Connection." Harvard Health Publishing, April 2021. 
3. Hadhazy, A., "Think Twice: How the Gut's 'Second Brain' Influences Mood and Well-Being." Scientific American, February 2010.