New Research Further Highlights Association Between Gut Bacteria and Mental Health

The human microbiome refers to the trillions of bacteria, fungi, viruses and other microorganisms that share your body and contribute to your overall health. Many of our organs have their own microbial inhabitants, including, perhaps most famously, the gut.

Research has shown that gut health is inextricably linked to mental well-being. In an effort to further understand the gut’s relationship to mental health, a team of researchers analyzed past studies that examined the gut microbiome of individuals living with such mental health conditions as depression, anxiety and bipolar disorder. Their findings reveal a biological overlap of certain gut bacteria in relation to these conditions.

The Research

Researchers looked at 59 case-control studies that evaluated gut-microbe diversity in adults living with major depressive disorder, bipolar disorder, psychosis and schizophrenia, anorexia nervosa, anxiety, obsessive-compulsive disorder, post-traumatic stress disorder, or attention-deficit/hyperactivity disorder.

The findings, published in JAMA Psychiatry, show that the gut microbiomes of individuals experiencing conditions like depression, bipolar disorder, and anxiety, are more likely to be high in pro-inflammatory bacteria and low in anti-inflammatory producing bacteria.

While these shouldn't be considered biomarkers of these conditions, the researchers suggest that gut health should be considered in the treatment of psychiatric disorders.

“Previous meta-analyses of genetic or inflammatory marker studies have reported similar findings, and we have now seen this in the microbiota, as well,” says study author Viktoriya Nikolova, a PhD student at King’s College in London. “This has important implications in how we understand, classify and treat mental health conditions.”

Nutritional psychiatrist Uma Naidoo, MD, author of the national bestseller “This Is Your Brain on Food,” says that highlighting another dimensional component of diagnosing certain conditions could lead to greater accuracy in clinical diagnoses.

“Where talking about the gut or digestive health may have emerged as yet another wellness trend, its importance from the perspective of holistic, whole-body well-being cannot be ignored,” Naidoo says. “The gut does not function simply for its own sake—it profoundly influences our mental health, as well, and this marks an important space for intervention when it comes to how we address mental illness.”

Naidoo notes that this awareness will not only allow for the development of new, targeted therapies that come from a “gut-brain” approach, but it could also empower individuals by increasing access to mental health interventions.

The Importance of Brain Food

Diet adjustments are a common prescription when it comes to concerns for our physical health. But what if it became common practice to include the foods we eat in our pursuit of mental well-being?

“While all the parts of our body are constantly communicating via chemical messengers, it’s compelling to note that the very same embryonic cells which form the brain also form the gut,” Naidoo says. “Thus, by feeding the gut with targeted nutrition, we directly feed the brain, too.”

But the future of treatment could be even simpler than that. An important part of this review’s findings showed that transplanting a sample of the microbiome of someone with symptoms of depression into another person elicited depressive symptoms in that person. The opposite was also found to be true.

“I do wonder if therapeutic intervention may go the route of replacing these strains alone, versus encouraging diet, lifestyle to empirically promote balance of the gut microbiome,” Naidoo says.

As we fill in the blanks of the gut-brain connection, questions continue to arise. But the future of research in this area looks bright, as the strength of these ties becomes more evident.

“A greater appreciation needs to be placed on gut health by both the people struggling with these conditions and their clinicians if we are to achieve better outcomes,” Nikolova says. “However, we still have a lot to learn about how we can translate what we found into treatment.”