The answer is most likely yes, your gut can cause anxiety. And make it worse!
Extensive studies have validated the presence of the brain-gut connection, with the bi-directional relationship between the two systems now clear and variable in its presentation. In this article, we’re going to help you understand the different ways digestion and your brain interact to either amplify your anxiety or create it in the first place.
Pre-COVID-19 studies suggest that just over a third of people will experience an episode of anxiety in their lives.[1]
In Hong Kong, an estimated 26 per cent of people have reported mental health deterioration since the pandemic began.[2] How these local and global numbers have increased coming to the beginning of 2022 remains to be seen.
Pandemic aside, for those with another illness such as irritable bowel syndrome (IBS), the prevalence of an accompanying anxiety disorder can be up to 70 per cent.[3] Panic attacks, social anxiety, generalised anxiety disorder (GAD) and other phobia based experiences are most prevalent. Regardless of their description, they can all be equally debilitating in their unique way.
In some cases, when I see people who present to me with anxiety, they have already identified it using their self-awareness or have had it diagnosed via another mental health professional. A common denominator is a burden that all carry, interfering with personal relationships, sleep and work productivity, amongst other things.
Introducing the gut-brain connection and how it is crucial in anxiety
In other articles, I’ve mentioned how often I have patients who have been offered a “get your stress under control” type of solution after being diagnosed with IBS. It’s fair to say now that this chicken and egg situation has flipped with the bacterial environment within the gut or microbiome having multiple influences on the emotional and cognitive centres of the brain.[4]
One of the clearest examples of the intimate relationship between the brain and the gut is the creation of serotonin. Ninety per cent of serotonin needed for regulating mood, behaviour and sleep, amongst a host of functions in the central nervous system, is made in the gut.[5] Now consider that the first option for treating anxiety within modern medicine is antidepressant therapy, making the brain and gut connection hard to overstate. It’s often a new piece of information for my patients. How about you?
The gut-brain axis also encompasses the hypothalamic-pituitary-adrenal (HPA) axis, among other vital networks, such as the central nervous system.
This axis expresses the relationship between the hypothalamus and the pituitary gland in the brain, two significant pillars linking the brain to the endocrine system that manages your hormones.[6] Together with the adrenal gland, the HPA axis is a central player in keeping balance, also known as homeostasis, and how the body uses energy and responds to stress.[7]
The HPA axis is part of the limbic system, a vital part of the brain predominantly involved in memory and emotional responses when it comes to anxiety. It is also considered the core axis that coordinates how the body responds to stress of any kind.[8]
Remember, the HPA axis is part of the gut-brain axis. Yep, the three pillars that govern how your body responds to the stimuli in its environment, externally and internally (I’m referring to your thoughts here), are under the influence of your digestion and the processes within it. It now brings us to the immune system and how it’s wise not to forget its conversations as part of the gut-brain axis and how this leads to anxiety.
Inflammation that originates in the brain can cause anxiety
Fun fact. Seventy per cent of the immune system resides in the digestive system.[9] To understand how the immune system, the brain, and digestion communicate in this sense, we need first to explore a couple of fundamentals.
The brain also has immune system representatives in the form of cells called microglia. Your microglia mature just two weeks or so after you’re born. Their main job is to survey their immediate surroundings (read, the brain) and maintain the homeostatic landscape crucial for our nervous system’s supercomputer to avoid any insults.
When there is an immune stimulus or some form of tissue damage, such as traumatic brain injury[10], microglia activate inflammation to either clear pathogens from infection or restore brain health. As is usually the case with these processes, they are essential to your and my survival. The problem occurs when the microglia fail to turn off due to some form of chronic stress.[11]
When the microglial cells stay activated, we see higher levels of inflammation in the brain.
Have you heard of the term neuroinflammation before?
If you are new to this, neuroinflammation is simply an inflammatory response localised in the brain and central nervous system, including the spinal cord.[12]
Neuroinflammation is one of the critical mechanisms for the onset of anxiety disorders, such as generalised anxiety disorder.[13] Sequentially, these same neuroinflammatory processes have been linked with the treatment resistance to antidepressant interventions used regularly as a first-line treatment in various anxiety conditions.[14]
The interaction between dietary fibre and your digestion influences neuroinflammatory processes and can suppress the immune response that causes anxiety.
Now that you are familiar with microglia, their job and the consequences of their long-term activation, there’s an important point. The gut-brain axis heavily affects microglia development in the first two weeks of life and their behaviour throughout life. One of the main ways this is thought to happen involves your diet.
The final metabolites (think end products) of your fibre consumption, called short-chain fatty acids (SCFA), can cross the blood-brain barrier (BBB), affecting the central nervous system and consequently the microglia.
As of writing this, though, the effects they have are unknown. Still, studies are looking into the role of SCFAs in influencing neuroinflammation, the creation of serotonin, building new neurons and other pathways that directly affect emotion, cognition and the development of other brain disorders.[15] A bonus to this is that another vital role of one of the particular SCFAs, butyrate. Butyrate strengthens the integrity of the blood-brain barrier, which can become leaky, just like the picture we see with leaky gut.[16]
The main takeaway here is that dietary fibre, which is also prebiotic, is, directly and indirectly, involved in your emotional and cognitive health, including anxiety. Following this, if you are low in fibre, then the functions of these short-chain fatty acids (SCFA) are less pronounced, potentially leading to more inflammation that can lead to anxiety.
Can probiotics help with the management of anxiety?
The answer is that it certainly seems so. There are a few different species that are important in helping people manage anxiety. I could write a whole article and plan on it, but why don’t we continue with neuroinflammation here.
Fun fact. Did you know that microbes, such as some well-known probiotic species, are involved in the production of neurotransmitters? So let’s try and break it down, so it’s easier to match the brain chemical with the probiotic:
- Acetylcholine (important for focus cognition) can be derived from the Lactobacillus species.
- GABA, the only inhibitory or relaxing neurotransmitter, can be derived from the Lactobacillus[17] and Bifidobacteria[18] species.
- Serotonin, often referred to as the mood chemical, can be derived from Enterococcus and Streptococcus species.[19]
One of the common themes that bring these probiotic-derived neurotransmitters together is their ability to, directly and indirectly, influence the microglial activation we’ve been talking about in this article.[20]
The connection between digestion and the brain may be contributing to your anxiety, and you can influence it.
It’s easy to see just how amazing our understanding of the systems of the body is becoming. More interesting to me, and hopefully, you, is how we can harness the bridges between these body systems to help ourselves and each other.
I hope this article shows that the conversation between the brain and digestion is exceptionally intimate, especially when it comes to anxiety. It can be challenging to know what is affecting what at any one time, especially when the immune system wants to have its say. This highly nuanced connection doesn’t mean that you can’t influence this conversation by assessing your daily fibre intake and looking into how probiotics might help your anxiety through the brain-gut link.
Someone equipped to help you understand yourself better, such as a councillor or psychologist, can help you with your anxiety.
I’ve just spent this long article talking about how the gut-brain connection plays a role in anxiety, from prebiotic fibre to probiotics and their relationship to your neurotransmitters. Still, before I conclude this article, I want to mention something important about anxiety.
Anxiety, restlessness, agitation and how you, or someone close to you, are experiencing it are unique and often caused by some more underlying patterns within your or your friend’s personality. I’m not necessarily referring to sickness or pathology there, but something a little more existential.
Still, it does mean that getting some counselling and talking about what’s going on is just as important as unlocking your gut-brain connection. Sometimes, not all the time, a way of thinking or even being hurt by something or someone decades ago can persist in such a way over time that you might never know it’s making you feel unsafe. Ok, lecture over.
Hope this article helps!
References
[1] Bandelow B, Michaelis S. Epidemiology of anxiety disorders in the 21st century. Dialogues Clin Neurosci. 2015;17(3):327-335. doi:10.31887/DCNS.2015.17.3/bbandelow
[2] Choi EPH, Hui BPH, Wan EYF. Depression and Anxiety in Hong Kong during COVID-19. Int J Environ Res Public Health. 2020;17(10):3740. Published 2020 May 25. doi:10.3390/ijerph17103740
[3] Remes O, Brayne C, van der Linde R, Lafortune L. A systematic review of reviews on the prevalence of anxiety disorders in adult populations. Brain Behav. 2016;6(7):e00497. Published 2016 Jun 5. doi:10.1002/brb3.497
[4] Carabotti M, Scirocco A, Maselli MA, Severi C. The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Ann Gastroenterol. 2015;28(2):203-209.
[5] Abdel-Haq R, Schlachetzki JCM, Glass CK, Mazmanian SK. Microbiome-microglia connections via the gut-brain axis. J Exp Med. 2019;216(1):41-59. doi:10.1084/jem.20180794
[6] Dr. Boeree, C. George. “The Emotional Nervous System”. The Limbic System. Viewed 18th November 2021.
[7] Miller WL. The Hypothalamic-Pituitary-Adrenal Axis: A Brief History. Horm Res Paediatr. 2018;89(4):212-223. doi:10.1159/000487755
[8] Carabotti M, Scirocco A, Maselli MA, Severi C. The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Ann Gastroenterol. 2015;28(2):203-209.
[9] Vighi G, Marcucci F, Sensi L, Di Cara G, Frati F. Allergy and the gastrointestinal system. Clin Exp Immunol. 2008;153 Suppl 1(Suppl 1):3-6. doi:10.1111/j.1365-2249.2008.03713.x
[10] Donat CK, Scott G, Gentleman SM, Sastre M. Microglial Activation in Traumatic Brain Injury. Front Aging Neurosci. 2017;9:208. Published 2017 Jun 28. doi:10.3389/fnagi.2017.00208
[11] Wang, YL., Han, QQ., Gong, WQ. et al. Microglial activation mediates chronic mild stress-induced depressive- and anxiety-like behavior in adult rats. J Neuroinflammation 15, 21 (2018). https://doi.org/10.1186/s12974-018-1054-3
[12] DiSabato DJ, Quan N, Godbout JP. Neuroinflammation: the devil is in the details. J Neurochem. 2016;139 Suppl 2(Suppl 2):136-153. doi:10.1111/jnc.13607
[13] Rooney, S., Sah, A., Unger, M.S. et al. Neuroinflammatory alterations in trait anxiety: modulatory effects of minocycline.Transl Psychiatry 10, 256 (2020). https://doi.org/10.1038/s41398-020-00942-y
[14] Rooney, S., Sah, A., Unger, M.S. et al. Neuroinflammatory alterations in trait anxiety: modulatory effects of minocycline.Transl Psychiatry 10, 256 (2020). https://doi.org/10.1038/s41398-020-00942-y
[15] Dalile B, Van Oudenhove L, Vervliet B, Verbeke K. The role of short-chain fatty acids in microbiota-gut-brain communication. Nat Rev Gastroenterol Hepatol. 2019;16(8):461-478. doi:10.1038/s41575-019-0157-3
[16] Dalile B, Van Oudenhove L, Vervliet B, Verbeke K. The role of short-chain fatty acids in microbiota-gut-brain communication. Nat Rev Gastroenterol Hepatol. 2019;16(8):461-478. doi:10.1038/s41575-019-0157-3
[17] Komatsuzaki N., Shima J., Kawamoto S., Momose H., and Kimura T.. 2005. Production of γ-aminobutyric acid (GABA) by Lactobacillus paracasei isolated from traditional fermented foods. Food Microbiol. 22:497–504. 10.1016/j.fm.2005.01.002
[18] Pokusaeva K, Johnson C, Luk B, et al. GABA-producing Bifidobacterium dentium modulates visceral sensitivity in the intestine. Neurogastroenterol Motil. 2017;29(1):e12904. doi:10.1111/nmo.12904
[19] Yano JM, Yu K, Donaldson GP, et al. Indigenous bacteria from the gut microbiota regulate host serotonin biosynthesis [published correction appears in Cell. 2015 Sep 24;163:258]. Cell. 2015;161(2):264-276. doi:10.1016/j.cell.2015.02.047
[20] Abdel-Haq R, Schlachetzki JCM, Glass CK, Mazmanian SK. Microbiome-microglia connections via the gut-brain axis. J Exp Med. 2019;216(1):41-59. doi:10.1084/jem.20180794
