Gut Feelings: Can probiotics treat depression?

By Lynette Roberts

Discipline of Clinical Psychology, Graduate School of Health, University of Technology Sydney

1 in 6 people will suffer from depression in their lifetime. This could be you or someone you know. Why do people experience this condition? Researchers have found that many things can contribute to depression including low levels of certain chemicals in your brain, your genetics, stressful negative life events, as well as your psychology; that is how you interpret and respond to situations.

Now researchers are beginning to discover that our mental health is also affected by our gut health. They call this the “gut-brain” axis. Understanding more about this link means that we can explore novel treatments for depression and other emotional disorders.

How do we know our gut health is important for our mental health?

The balance of good to bad bacteria is important. We need bacteria in our gut for important body functions such as; to help us digest food, support the growth of beneficial bacteria in the gut, communicate with the immune system, and influence brain function. We can see that people with depression have different gut compositions than people without depression. People with gut issues like irritable bowel syndrome (IBS) also have higher rates of anxiety and depression. Finally, if you transplant fecal matter from depressed adults to mice, then the mice will get depressed. Overall, these studies show us that there is something different about the gut bacteria in people who are experiencing depressive symptoms.

Interesting research shows us that our gut and brain communicate with each other. 

Researchers are beginning to work out how our gut, brain and mood are all connected. There is a direct connection via the “vagal nerve”, where the gut can directly communicate with the brain. There are also indirect pathways involving the interaction of our stress, immune and central nervous systems. For instance, chronic stress, poor diet, and antibiotics, can affect the health of our gut, particularly the lining or barrier that keeps bacteria within our gut and out of our bloodstream. If our gut is ‘leaky’, toxins can cross into our bloodstream, activating the immune system and causing an inflammation response, where these “pro-inflammatory cytokines” can alter the production of chemicals important in regulating our mood.

Where do probiotics fit in?

Probiotics are beneficial bacteria for our gut that can be found in cheese, natural yoghurt and other fermented products. Probiotics can help ‘plug the holes’ in an inflamed and leaky gut. We know that when you give probiotics to depressed and anxious rats, healthy human volunteers, or people with gut issues like IBS, they all feel better! We see improvements in thinking, distress, and brain activity, as well as reduced levels of cortisol, a stress hormone.

A new treatment for depression?

There is no magic bullet for a complex and multifaceted condition like depression. However, probiotics may offer an additional treatment option, either by itself or in conjunction with other established treatments, to help treat depressive symptoms. Researchers are now starting to look at whether probiotics can be useful as treatment for people experiencing depression

Interested in participating?

We are currently investigating whether probiotics can be used to treat depression through a clinical trial at the University of Technology Sydney, Australia. Participants in the study either drink a probiotic or a placebo daily for 8 weeks. We won’t know which one it is either until the end of the study, to reduce bias when we look at the results. This is known as a “double blind” trial. To see the effects of the supplement, we also take measures of participant’s physical and mental health at the start and at the end of the study. The probiotics are safe and well-tolerated. Participants receive $50 gift certificate for taking part in the study. If you’re interested in helping us find out more about the effects of probiotics on depression, the last day for enrolment for the year is October 21st 2016, and can be done here.

Studies like the one we’re running can help us work out whether probiotics in the treatment of depression, are indeed “science or science fiction?”