Select Page

Is Your Gut Bacteria Causing Your Depression?

Nearly 1 in 5 in the UK showed signs of depression or anxiety and rates are increasing every year.

We usually look for external sources of stress that might be the cause of our depression.

But could it be due to tiny alien invaders that live in our gut?


What Is the Gut Microbiome and Why Is It Important?

The gut microbiome is what most people mean when using the term ‘gut bacteria’.
The gut microbiome, as defined by molecular biologist Joshua Lederberg, is the totality of microorganisms, bacteria, viruses, protozoa, fungi and their collective genetic material present in the gastrointestinal tract (GIT).

I decided to write on this subject as it’s becoming a popular area of research – in the 1980s there were only 11 studies published on this subject, it was over 1300 in 2018.

I was amazed to find that there was a Human Microbiome Project set up in 2007, its aim as a research initiative is to improve understanding of the microbial flora involved in human health and disease. This initiative is huge and has a large financial backing.

As I’ve read more into this subject, I found it fascinating that we can be affected so much by our gut bacteria. This symbiotic relationship between our body and these tiny bacterial foreign invaders shows that they at least play some role in our mental and physical health.

I think this is also an interesting topic as many of us feel that we have this transcending, unaffected consciousness that we have complete control over. This doesn’t (in my opinion) seem to be the case. Maybe free will is an illusion. Another topic for a future article perhaps?

We have other examples of this symbiotic relationship in nature. A certain fungus infests ants, turning them into a zombie-like state. This fungus then takes over their jaw muscles and forces them to bite down on a leaf or stem of a plant. This is after the fungus instructs them to climb to the highest nearby plant. Fungal stalks start growing out of their head that will eventually release spores that rain down on the ants below, in turn affecting them.

A little creepy, huh?


Another example is the Toxoplasma Gondii parasite. It takes up residence in the brains of rats and suppresses their fear of cat urine. It also stimulates the pleasure centres responsible for sexual behaviour that normally activate after exposure to a female rat.

So not only do they not fear the cat but they are attracted to them. As you can imagine, a rat rampaging towards a cat is only going to end in one way.

Why would a parasite want its host to be eaten?

So it can reproduce in the cat’s stomach.

The cat sheds this parasite in its faeces, other rats eat the food or water contaminated with cat faeces and the cycle repeats.

I hope those examples weren’t too grim but I think they illustrate the point that foreign organisms can affect us in ways we might not think (and I find this stuff fascinating).

Is There a Link Between Gut Bacteria and Depression?

I spent hours and hours of reading and to sum up:

Human and animal studies provide evidence for implying a strong link (Studies listed 7-11) between the gut microbiome composition and the development of mental disorders such as depression and anxiety.

So the answer to this question: yes, but it is just a link. Meaning, it seems to be strongly correlated but not yet proven. 

The gut bacteria in your intestinal tract seems to form a microbiome-gut-brain axis. Some microbes can cause anxiety and depression by affecting certain neurotransmitters in the brain that modulate behaviour (GABA-ergic, glutaminergic NMDA, and serotonergic 5HT1A receptors).

Let’s look at the GABA neurotransmitter as an example.

This is a naturally occurring inhibitory neurotransmitter, it blocks, or inhibits, certain brain signals and decreases activity in your nervous system. When GABA attaches to a protein in your brain known as a GABA receptor, it produces a calming effect.

This can help with feelings of anxiety, stress and fear. A microbe called Evtepia gabavorous gobbles up with GABA (in your gut), therefore your brain can no longer calm itself. This means you may be feeling anxious because of this microbe and not due to some external stress.

You may have heard of the medication called Gabapentin, this is used for pain that arises from the nervous system and has a calming effect. This medication works on the same receptors as the GABA molecule.

Another example (stay with me!), patients diagnosed with major depressive disorder (MDD) have a different faecal microbiome profile compared with healthy individuals.

MDD patients seem to show the increased presence of certain bacteria (Bacteroidetes, Protobacteria, and Actinobacteria) and less of another (Faecalibacterium). The latter has been shown to have the opposite effect on depression when there are increased numbers in the gut.

There may be another indirect mechanism on how the gut bacteria can adversely affect our mental health too. There have been several links made with certain gut bacteria and inflammation. We know there is a link between inflammation and depression. Therefore this bacteria’s ability to affect inflammation might be a cause, although it’s likely to be a combination of several factors. 

I will stop there for fear of losing people to information overload and preventing this article from becoming painfully long.

I feel like this has made my point, although believe me, this is the tip of a very humongous iceberg. I feel so lucky to be born in a time when so many dedicated scientists are working on this and so many studies are being published each day.

To round things off, let’s take a look at how we might be able to ensure we benefit from positive bacteria in our guts. 


How Can We Improve Our Gut Microbiome?


There is a great article that explains how the industrial world we live in has negatively shaped our microbiome by recent progress in medicine, food and sanitation.

Processed foods, infant formula, modern medicines and sanitation have all contributed to a negative impact on our gut microbiomes. Even being born by C-section (as opposed to vaginally) can adversely affect the infant’s gut biome in the short term.

I’ve tried to find advice for things we all can do in our daily lives. These are not solutions like fecal transplants. Yes, they are a thing (and the most promising way of fixing faulty gut biomes) and no you should not try this at home (I’ve read stories that people have). Most of the advice is not rocket science, but if you implement some of these, they could have a beneficial effect.

1. Eat Microbiota-Accessible-Carbohydrates

 Examples are legumes and wholegrains (like oats and barley).

2. Eat fermented foods 

Kefir, kimchi, miso and sauerkraut. You can try kombucha which is my favourite way of getting fermented foods (it’s a type of tea). Kombucha is great and comes in different flavours containing no sugar. Not to mention they taste amazing. 

3. Eating less processed foods

Shocker!! Including sugar. 

4. Golden kiwi fruit 

This one isn’t so obvious. I’ve read studies that found that this helped Faecalibacterium (the bacterium I mentioned before). Researchers used it in supplement form called Livaux. Now this seems a little hard of getting hold of and possibly expensive. So I’m unsure of the cost-benefit ratio.

5. Eat more vegetable and fruits

Especially asparagus, bananas, chicory, garlic, Jerusalem artichoke and onions.

6. Reduce Stress 

Which, if we could do with a simple click of our fingers, I’m sure we all would. But just think you have to do it for your little helpless gut bacteria. Studies show that stressors reduce the variety of gut bacteria. Stressors include sleep deprivation – you can read my article on how to get a good night’s sleep here.


I think that’s enough for the time being. Remember to write some of these pointers down so you are more likely to implement them.

I hope you enjoyed this and that it shows how taking care of our bodies, inside and out, is vital for all-round good health. Good luck!

Studies Featured

Join Us

Get our latest ways to improve your health & wellbeing, straight to your inbox. Nothing else.

Produced with Fellow