A Gut Feeling

By Kristin Hirsch

Depression is a highly prevalent disorder in the United States, with approximately 16 million people experiencing at least one major depressive episode in a given year. This disorder is associated with memory problems, blunted emotions, negative worldviews,w social withdrawal, and many other symptoms. Some people have treatment-resistant depression, which doesn’t get better with the medicine on the market today. Since depression can be a debilitating disorder, it’s important that we have enough different treatment options for everyone to have the opportunity to recover from depression. The bacteria in our gut, collectively known as gut microbiota, have been shown to regulate many functions in our bodies, including brain function and mental health. Because of this, changing the health of our gut microbiota could be an effective way to treat mental disorders such as depression. Understanding how gut microbiota influence mental health may allow us to develop treatments that would prevent or treat depression, and doing so will help improve the overall life satisfaction of countless people.

The gut microbiota and the brain communicate through the microbiota-gutbrain axis, and what happens in one area likely relates to what happens in the other. Gut microbiota can alter brain function and mental health using neurotransmitters, the chemical messengers which tell the nervous system how to function. When gut microbiota are out of balance, they cannot communicate properly with the brain, and mental health issues are more likely to arise.

Surprisingly, depression can be caused by using certain medications. Antibiotics, for example, may help us ward off conditions such as urinary tract infections and strep throat, but they also destroy the good bacteria in our gut that keep us healthy. Because they kill helpful gut bacteria, antibiotics cause microbiota dysfunction and increase our chances of other complications, such as depression. Several studies have found that there is a positive correlation between antibiotic doses and higher depression risk, meaning that the more antibiotics you take, the greater risk you have of developing depression. This effect can last for up to ten years after taking antibiotics, so it is best to use antibiotics sparingly, especially if there is a history of mental illness in your family.

Another common yet unavoidable issue, which negatively impacts our health, is stress. While some stress is necessary for us to perform well in high-pressure situations, chronic stress can be detrimental to our health. When our stress response system is activated for too long, it becomes fatigued and stops functioning properly. This leaves us susceptible to immune system complications, and since gut microbiota are related to both our immune system and our brain functioning, a weakened immune system can lead to a depressed mind.

One way to improve dysregulated gut microbiota is to use probiotics, or live beneficial bacteria, and prebiotics, or nondigestible fiber which promotes growth of healthy gut bacteria. In chronically stressed people, prebiotics have reduced extended stress response activation, improved gut microbiota dysregulation, and influenced people to view life more positively. Some probiotics have had similar effects. One strain decreased people’s stress levels and improved their memory, another improved people’s ability to have emotional responses, and a final probiotic strain improved depressive symptoms and gastrointestinal problems in people with irritable bowel syndrome and depression.

Although more research is required before we fully understand the relationship between gut microbiota and depression, improving our gut microbiota health may be a safer and more effective way to treat mental illnesses. A healthy gut can properly communicate with our brains to keep us functioning at our best, and it seems that we may be headed in the right direction to create treatment options for those with treatment-resistant depression.