The Gut Brain Connection and Its Impact on Mood, Behaviour and Mental Health
- 3 days ago
- 7 min read
I'm an international holistic health practitioner, specialising in supporting individuals with ADHD, autism, allergies, sleep issues, and gut problems using natural medicine. I help people uncover and treat root causes so they can reclaim their health and thrive.
For decades, mental health was considered solely a brain issue, dominated by neurotransmitters, psychology, stress, trauma, genetics, and medication. Emerging research now reveals a far more complex and hopeful reality, mental health is profoundly connected to the gut. Your brain is not working in isolation.
Hidden within the digestive tract lives an entire ecosystem of bacteria, mycobiota, and other microorganisms that are in constant communication with the brain every second of the day. This intricate communication network, now known as the gut-brain axis, is rapidly transforming the way we understand mood, anxiety, depression, neurodiversity, and emotional wellbeing. Most importantly, it helps explain why so many people struggling with mental health symptoms also experience digestive issues, inflammation, fatigue, food sensitivities, sleep disturbances, and immune dysregulation. Assisting my patients with these conditions makes up a large part of my clinical practice.
The gut and brain are not separate systems. They are deeply intertwined.
Your gut is constantly talking to your brain
Inside the digestive tract live trillions of microorganisms collectively known as the gut microbiome. Once thought to simply assist digestion, we now understand that these microorganisms influence almost every major system in the body, including the nervous system, immune system, hormones, and brain chemistry. In fact, there is almost no function in the body untouched by the microbiome.
What happens in the gut can influence mood and emotional regulation, stress resilience, sleep quality, inflammation, cognitive function and concentration, behaviour, immune responses, hormone balance, and neurotransmitter production. This communication occurs through multiple pathways, including the vagus nerve, inflammatory signalling, immune messengers, and microbial metabolites. The gut is, quite literally, in conversation with the brain.
The surprising link between gut health and neurotransmitters
One of the most fascinating discoveries in recent years is that many neurotransmitters associated with emotional wellbeing are heavily influenced by the gut.
Serotonin, often referred to as the “feel-good” neurotransmitter, is predominantly produced in the digestive tract. The gut microbiome also influences dopamine and GABA, key neurotransmitters involved in motivation, calmness, emotional stability, and stress regulation. When the gut microbiome becomes disrupted, neurotransmitter production and signalling can also become impaired.
This imbalance, known as dysbiosis, occurs when beneficial bacteria are overcrowded by inflammatory or opportunistic microbes. Dysbiosis has been associated with increased inflammation, altered stress responses, digestive symptoms, anxiety, low mood, irritability, and even behavioural changes. For many individuals, mental health symptoms may not simply be “all in the head.” They may be deeply connected to what is happening in the gut.
Inflammation: The missing piece in mental health
One of the strongest emerging themes in modern research is the role of inflammation in mental health conditions.
Chronic inflammation can alter neurotransmitter activity, increase oxidative stress, disrupt brain signalling, and influence emotional regulation. Inflammatory chemicals produced in the gut can travel throughout the body and communicate directly with the brain.
This may help explain why individuals with inflammatory conditions often experience anxiety, depression, brain fog, fatigue, poor concentration, mood instability, and sleep issues.
Many everyday factors can contribute to inflammation and microbiome disruption, including ultra-processed foods, high sugar intake, chronic stress, pesticides and environmental toxins, antibiotics, poor sleep, excess alcohol, artificial additives, and food intolerances. Over time, this inflammatory load can begin affecting both physical and emotional health. The body keeps score, and often, the gut speaks first.
Children, behaviour, and the gut-brain axis
This connection becomes particularly important when working with children experiencing emotional or behavioural challenges.
In clinical practice, many children struggling with anxiety, emotional dysregulation, hyperactivity, poor focus, aggression, sensory issues, or low mood also present with digestive disturbances, food sensitivities, constipation, eczema, recurrent infections, parasites, or sleep problems. The overlap is rarely coincidental.
Children may express anxiety very differently from adults. Rather than verbalising worry, they may exhibit irritability, meltdowns, stomach aches, headaches, sleep disturbances, emotional outbursts, clinginess, poor concentration, regression in behaviour, or fussy eating.
The gut microbiome plays a powerful role in regulating stress responses and nervous system function during childhood development. When the gut is inflamed or imbalanced, children may become more reactive, more emotionally overwhelmed, and less resilient to stress. This is one reason why supporting gut health can become an important piece of a holistic mental health approach.
Food, mood and microbial diversity
The microbiome thrives on diversity. A wide variety of colourful wholefoods, fibres, and fermented foods helps nourish beneficial bacteria and strengthen the gut ecosystem. Prebiotic foods such as garlic, onions, leeks, asparagus, oats, and legumes feed beneficial bacteria, while probiotic foods such as kefir, sauerkraut, kimchi, and yoghurt can introduce beneficial strains into the gut. The Western diet, however, often lacks the fibre and diversity needed to sustain a healthy microbiome. Highly processed foods rich in sugar, refined carbohydrates, and additives may fuel inflammation while reducing microbial diversity. Research and clinical practice continue to suggest that dietary patterns rich in whole foods, omega-3 fats, antioxidants, and plant diversity are associated with better mental wellbeing and lower rates of depression and anxiety. Food is not simply calories, it is information for the brain, immune system, and microbiome.
Stress works both ways
Many people think stress only impacts the mind, but stress profoundly alters the gut. When the nervous system remains stuck in chronic fight-or-flight mode, digestion slows, stomach acid changes, intestinal permeability may increase, and beneficial bacteria can decline. At the same time, an unhealthy gut can increase stress sensitivity and amplify anxious feelings or depression. This creates a vicious cycle in which stress disrupts the gut, a gut imbalance worsens mood, a low mood increases stress, and chronic inflammation intensifies the cycle. Supporting the nervous system and microbiome together is often far more effective than addressing either in isolation.
A more integrated approach to mental health
Mental health is complex and deeply individual. There is rarely one single cause behind anxiety, depression, or emotional dysregulation. However, what we now know is that the gut profoundly matters. While psychological support, trauma care, lifestyle medicine, and appropriate medical intervention remain incredibly important, the microbiome has emerged as a powerful missing link in the mental health conversation.
Supporting gut health may involve improving diet quality, reducing inflammatory foods, addressing food intolerances or food allergies, increasing fibre and plant diversity, supporting sleep, reducing toxic load, managing stress, restoring healthy microbial balance, and improving digestive function. These foundational changes can have ripple effects throughout the entire body, including the brain.
The future of mental health is more holistic
Science is finally beginning to validate what many holistic practitioners have observed clinically for decades, the brain cannot be separated from the body. In 1992, my naturopathic lecturer used to say, "It all starts in the gut." From 2009 to 2011, I was working with an orthomolecular psychiatrist, Prof. Dr. Michael Maes, in an integrative health and wellness center. At that time, he was conducting research on the microbiome and depression and publishing his groundbreaking findings.
For many individuals, mental health symptoms may not simply be “all in the head.” Gut microbiome disruption can impair neurotransmitter production and signalling. They may be deeply connected to what is happening in the gut. Serotonin helps regulate mood, sleep, emotional resilience, and feelings of wellbeing. When serotonin levels become disrupted, individuals may experience anxiety, low mood, irritability, overwhelm, poor sleep, or a loss of enjoyment in things they once loved. Dopamine is closely linked to motivation, focus, reward, and pleasure pathways in the brain. Low dopamine activity may contribute to poor concentration, fatigue, emotional withdrawal, addictive tendencies, low motivation, and feelings of hopelessness. GABA, or gamma-aminobutyric acid, acts as the nervous system’s calming neurotransmitter. Healthy GABA activity helps promote calmness, relaxation, emotional regulation, and restful sleep. When GABA signalling is impaired, individuals may experience racing thoughts, heightened anxiety, inner tension, overstimulation, and difficulty switching the brain off.
The future of mental health care may not lie solely in silencing symptoms but in understanding the conversations happening throughout the body, especially between the gut and the brain. Frequently, healing the mind begins by nourishing the ecosystem within, and nothing does this better than natural medicine.
Discover which neurotransmitters may be affecting your mood and wellbeing
If you’ve recognised yourself or your child in symptoms such as anxiety, overwhelm, low mood, poor focus, emotional dysregulation, or sleep issues, your neurotransmitters may be playing a much bigger role than you realise. I’ve created a Neurotransmitter Assessment designed to identify patterns associated with key brain chemicals, including serotonin, dopamine, and GABA. This practitioner-designed questionnaire explores which neurotransmitters may be imbalanced and provides practical everyday strategies to help support healthier neurotransmitter balance through daily activities.
For those wanting deeper personalised support, you also have the option to book a one-on-one consultation where we can explore root causes contributing to symptoms, including gut health, inflammation, food sensitivities, nervous system dysregulation, sleep, stress, nutritional imbalances, and lifestyle factors. Together, we work to create an individualised and holistic path toward improved mood, behaviour, focus, and overall wellbeing. Here is my link.
Read more from Tina Horrell
Tina Horrell, Natural Health Care Practitioner
Tina Horrell is an integrative homeopath and naturopath with over 25 years of international experience. Tina supports individuals and families with a range of health concerns, specialising in autism, ADHD, allergies, gut issues, and sleep problems. She also offers targeted detox programs for heavy metals and environmental toxins. Her work blends homoeopathy, nutrition, herbal medicine, and detoxification to restore clients' balance and vitality, mentally, emotionally, and physically. Tina consults with clients worldwide via online video sessions and is a regular health writer for Brainz Magazine.
References:
John F. Cryan & Ted Dinan (2012). Mind-altering microorganisms: The impact of the gut microbiota on brain and behaviour.
Michael Maes et al. (2008). The gut-brain barrier in major depression: Intestinal mucosal dysfunction with an increased translocation of LPS from gram negative enterobacteria (“leaky gut”) plays a role in the inflammatory pathophysiology of depression.
Foster, J. A., & McVey Neufeld, K. A. (2013). Gut-brain axis: How the microbiome influences anxiety and depression. Trends in Neurosciences, 36(5), 305–312.
Ngo, D.-H., & Vo, T. S. (2019). An Updated Review on Pharmaceutical Properties of Gamma-Aminobutyric Acid. Molecules, 24(15), 2678.
