How Gut Bacteria and Depression Are Connected

Have you ever had a “gut feeling” about something? This phrase, often used to describe intuition, may have more to do with your actual gut than you think. Research shows a fascinating connection between your gut and brain; this is just one of the many ways your body and mind interact, and is commonly referred to as the gut-brain axis.

Maintaining a healthy diet and exercising regularly are known physical ways to care for your mental health. These time-tested methods prove that taking care of your physical health can affect your mind. It turns out that taking care of your gut may also help improve your mood. 

Researchers and medical experts have become increasingly interested in how gut bacteria, which were thought to have only one role—helping with the digestive process—can potentially impact mental health. We'll explore the state of research about the gut-brain connection and suggest practical tips for caring for your gut for a healthier body and a happier mind.

Gut Bacteria and Depression

The idea that your gut bacteria can affect your mental health, including conditions like depression, is backed by a growing body of scientific research. These studies show that the types and amount of bacteria in your gut can affect your brain chemistry and, in turn, your mood and susceptibility to developing certain mental health conditions, such as depression.

Gut Health and Inflammation

There’s evidence that gut bacteria influence inflammation throughout your body. Inflammation has been linked to numerous conditions including depression in several studies. In a 2020 report, it was found that certain gut microbiota were associated with markers of increased inflammation that may contribute to the development of depression, suggesting a connection.

There is a bi-directional relationship between our gut and our brain, with some research showing a connection between stress and dysbiosis (a negative imbalance of good to bad bacteria), which may result in increased inflammation in the body. Chronic inflammation may be linked to anxiety and depression in some individuals, says Kara Landau, a registered dietitian at Gut Feeling. 

The Role of Serotonin

Serotonin is a key chemical messenger connected to your mood. This neurotransmitter is mostly produced in your gut; in fact, more than 90% of the serotonin your body produces comes from the intestine. In fact, certain gut bacteria may secrete serotonin.

There are many ways in which your gut can potentially influence your mood. Although there is limited evidence to support that specific ways of taking care of your gut with particular medications and therapies can improve mental health symptoms, one recent review did suggest a potentially beneficial role of probiotics on depression and anxiety. 

The Role of Gut Bacteria in Mental Health

When you think about factors that could affect your mental health, you’re generally likely to consider things like stress and genetics. If you have a family history of mental illness, for example, you’re more likely to develop one yourself.

These tiny organisms do more than help you digest food; they can possibly affect how you think, feel, and even how you handle stress. The gut-brain axis refers to the connection between your gut and brain. This connection goes both ways: your brain sends signals to your stomach when you’re hungry or thirsty, while your gut sends signals to your brain that affect your emotions and how your brain processes information. 

Bacteria in our gut influence gut functioning and can either increase or decrease states of inflammation, partly through effects on the vagus nerve, says Timothy Sullivan, MD, chair of Psychiatry and Behavioral Sciences at Staten Island University Hospital.

Inflammation itself leads to the production of substances such as cytokines that influence mental functioning, including mood. In addition, gut bacteria directly produce neurotransmitters like GABA and other substances that are psychoactive; and play a role in regulating our body’s stress response.

Anxiety

Studies have found a link between the balance of bacteria in your gut and anxiety. In one report, researchers found that people with social anxiety disorder have different types and amounts of gut bacteria compared to those without the disorder. This difference in gut bacteria may affect brain function and anxiety levels.

A diverse and balanced gut microbiome doesn’t just help with digestion—it can make you more resilient to stress. Some studies show that people with healthier gut bacteria tend to have a better emotional response to stress and may stay calmer in challenging situations.

Cognition

Your gut bacteria can also influence your memory and decision-making skills. There is increasing evidence of the association between your gut bacteria and cognitive functioning. Although the mechanism of this is not entirely clear, it is known that your gut bacteria produce a variety of neurotransmitters and hormones which have significant effects on cognition in the brain.

What Influences Your Gut Bacteria? 

Your gut bacteria are affected by numerous factors. Understanding what influences them can help you better care for your mental and physical health through your gut.

Diet

Unsurprisingly, what you put in your body is probably the most significant factor in determining your gut microbiota composition. Foods rich in fiber, like fruits, vegetables, and whole grains, promote the growth of beneficial bacteria. 

On the other hand, a diet high in processed foods and sugars can favor harmful bacteria, upsetting your gut balance. Probiotics found in yogurt and fermented foods like kimchi and sauerkraut can also help boost the diversity of your microbiome. When it comes down to it, what you eat matters.

The goal is to figure out which foods can boost gut health and, as a result, mental well-being. Landau recommends turning to an anti-inflammatory and gut-friendly diet to support mood and anxiety health. This would include enhancing nutrients such as prebiotics and probiotics, dietary fiber, omega 3’s, Vitamin D, and even vitamins and minerals such as B6 and magnesium, known to play a part in the serotonin pathway.

Stress

The effects of stress on your mental and physical health are well documented, and your gut health isn’t exempt. Chronic stress can make your gut less hospitable, leading to a decrease in microbial diversity and an increase in the types of bacteria associated with poor health. Managing stress through meditation, exercise, and getting enough sleep can help maintain a healthier gut microbiota.

Medications, especially antibiotics, which are crucial for treating infections, can also impact many of the good bacteria in your gut, disrupting the balance. Other medications, like antacids and anti-inflammatories, can also affect your microbiome. If you have to use any of these medications, it’s crucial to consult with your healthcare provider first.

Lifestyle Choices

Besides diet and stress, lifestyle choices like drinking alcohol excessively, smoking, and not getting enough exercise can affect your gut bacteria. On the other hand, there is some evidence regular exercise can increase the diversity of gut bacteria, which is linked to better health. 

Our microbiome is affected principally by diet but also by stress, bodily states (infection and inflammation, and other illnesses), and medications, in particular antibiotics. Dr. Sullivan says the best approach to sustaining a healthy gut is minimizing sugar and fatty foods and adopting a diet similar to the often-mentioned Mediterranean diet.

How Gut Bacteria Can Help

The gut-brain axis provides a two-way communication system where not only does your brain influence your guT, but also your gut health can directly impact your mood and emotional well-being. A balanced gut microbiome produces various chemicals and hormones that are critical for brain health, including those that influence your mood.

Some observational studies have shown that patients with major depressive disorder (MDD) have distinct microbial patterns that might be associated with their symptoms.

Modulating these bacteria through dietary interventions could potentially provide a unique approach to treatment, complementing traditional therapies like medication and psychotherapy​​​​, says Scott Keatley, a registered dietitian and co-owner of Keatley MNT, a private nutrition practice in New York.

Increasing studies have explored how dietary changes and probiotics can impact mental health. For example, a 2023 report found that people who followed a diet rich in certain prebiotics experienced less depressive symptoms than those who did not.

How to Incorporate Probiotics

Some researchers are pretty excited about the potential of adding probiotics to your diet and its effect on your mental health. Probiotics are live bacteria and yeasts that are good for your health influencing your digestive system. Studies show that these beneficial microorganisms can help restore the balance of the gut microbiome, which factors like poor diet, stress, and medication use can disrupt.

According to Landau, probiotic supplements can help boost the good bacteria that may have dropped due to lifestyle choices that negatively impact our gut bacteria. She recommends being clear on which strains you are taking in regard to which health condition.

While the efficacy of treating depression by focusing on gut health is still being studied, current research supports the idea that caring for your mental health by paying attention to your overall physical health, including your gut health, is beneficial.

It’s clear that what you eat, how you live, and how you manage stress significantly affect your gut bacteria and, by extension, your mental well-being. 

Final Thoughts on Your Gut and Your Brain

If you’re considering changing your diet or lifestyle to improve your gut health and mood, speak to your healthcare provider. They can guide you on the best changes to make based on your health needs and whichever conditions you may be dealing with.

The brain alone isn’t responsible for mental well-being; it’s also influenced by the trillions of microorganisms in your gut. Alongside traditional treatments for mental health conditions, such as medication and psychotherapy, dietary and lifestyle changes to improve gut health could play an important role. While more research is needed to understand how exactly this works and the most effective methods, the current studies are encouraging.

According to Keatley, maintaining a healthy gut microbiota through diet, lifestyle choices, and potentially the use of prebiotics and probiotics can be a valuable component of a comprehensive approach to mental health, particularly in managing your mood. As research evolves, the gut-brain axis could become a key target for developing novel psychiatric treatments.