How the Brain and Gut Communicate—and Why It Matters for GI Conditions.
Written by Anna Katherine Black, PhD
Licensed Clinical Psychologist
GI Psychology
The gut and the brain are in constant, two-way conversation. This connection is known as the gut-brain axis, a complex communication network linking your central nervous system (the brain and spinal cord) with your enteric nervous system (the ‘second brain’ in your gut). It plays a crucial role in how we digest food, manage stress, and process pain. For people living with chronic gastrointestinal conditions like Inflammatory Bowel Disease (IBD) and Disorders of Gut-Brain Interaction (DGBIs) such as Irritable Bowel Syndrome (IBS), understanding this axis is not just fascinating—it’s vital.
What Is the Gut-Brain Axis?
At its core, the gut-brain axis is a bi-directional system involving neural pathways, hormones, neurotransmitters, and immune signals. This system ensures that the brain can send signals to the gut—and vice versa. For example, have you ever felt “butterflies” in your stomach before a big presentation? That’s the gut-brain axis at work.
The vagus nerve, a key player in this system, serves as the main communication highway. It allows messages to travel rapidly from the brain to the gut and back. Alongside this, gut microbes produce neurotransmitters like serotonin and GABA, which influence mood and cognition. In fact, over 90% of the body’s serotonin is found in the gut.
When this communication system is healthy, digestion runs smoothly and emotional regulation feels more manageable. But when it’s dysregulated—due to chronic stress, illness, trauma, or inflammation—it can disrupt digestion, amplify pain signals, and worsen mental health symptoms.
One crucial part of this system is the autonomic nervous system, which includes the sympathetic nervous system (fight or flight) and parasympathetic nervous system (rest and digest). When we experience prolonged stress or anxiety, the sympathetic system stays activated, slowing digestion and increasing gut sensitivity.
This is why the gut-brain axis is so important in digestive health: it doesn’t just process what we eat, but how we feel while eating and digesting. It explains why stress can trigger cramps, urgency, or nausea, and why gut inflammation can lead to low mood or fatigue.
Gut-Brain Axis in IBD and DGBIs
Conditions like Crohn’s disease and ulcerative colitis are not just physical; they impact emotional and mental well-being. Research shows up to 57.6% of people with active IBD experience anxiety, while up to 33% report PTSD-like symptoms (Barberio et al., 2021; Petrik et al., 2024).
Even during remission, many patients continue to suffer from pain, bloating, or diarrhea. These symptoms often stem from overlapping Disorders of Gut-Brain Interaction like IBS. In fact, studies estimate that 30-60% of IBD patients in remission also experience functional GI symptoms (Gracie & Ford, 2017).
Key factors include:
- Visceral hypersensitivity: an enhanced response to normal gut activity. For example, a small amount of gas or digestive movement that wouldn’t bother most people might cause pain, bloating, or urgency in someone with IBS or IBD. This happens because the gut is more sensitive and the brain is amplifying those sensations.
- Hypervigilance: the tendency to constantly scan the body for symptoms or discomfort or scan the environment for potential “triggers” (e.g., foods). While it’s understandable for someone who has experienced unpredictable flares or pain, this high-alert state can actually increase awareness of minor symptoms and make them feel more intense.
- Catastrophizing: when a person expects or fears the worst outcome from symptoms (e.g., “This cramp must mean a flare is coming”). This mindset increases stress and can heighten the brain’s pain response, further activating the gut-brain loop.
These patterns are not imagined. They are deeply rooted in how the brain and gut interact under chronic stress or past trauma.
Targeting the Gut-Brain Axis: CBT and Clinical Hypnosis
Treatments like Cognitive Behavioral Therapy (CBT) and clinical hypnosis offer evidence-based approaches to recalibrating the gut-brain axis.
- CBT helps patients identify and challenge unhelpful thoughts (like catastrophizing) and develop healthier behavioral responses to GI symptoms. It has shown significant improvements in pain self-efficacy, social functioning, and quality of life, while reducing anxiety, depression, and avoidance behaviors (Chen et al., 2021).
- Clinical hypnosis, particularly gut-directed hypnosis, uses guided relaxation and imagery to reduce visceral hypersensitivity and calm the sympathetic nervous system. Clinical trials show benefits such as longer remission, reduced inflammation, and fewer flares (Keefer et al., 2013; Mawdsley et al., 2008).
These tools work not because symptoms are “in your head,” but because your head and gut are part of one intelligent system.
Supporting Recovery Through Self-Efficacy and Positive Expectancy
When patients believe they can influence their health, they are more likely to engage in helpful behaviors. In GI psychology, we call this self-efficacy. It’s the foundation of CBT and hypnosis, where patients learn to self-regulate their stress responses and trust their ability to manage symptoms.
Positive expectancy isn’t magical thinking. It’s a well-documented phenomenon where belief in treatment can enhance its effects. For IBD and DGBI patients, building balanced, hopeful thinking patterns can counteract the fear-driven loops of hypervigilance and catastrophizing.
A Holistic Path Forward
The science is clear: digestive health is deeply influenced by the gut-brain axis. By addressing the psychological and emotional aspects of GI disorders through mind-body interventions, patients experience real, measurable improvements.
It’s not about being more positive. It’s about being more connected—to your body, to your values, and to effective care.
Looking for Help?
Schedule a consultation or explore evidence-based resources, or contact us at admin@gipsychology.com to learn more about how GI Psychology can support your journey.
References
Barberio, B., et al. (2021). Anxiety and depression in inflammatory bowel disease: a systematic review and meta-analysis. J Crohns Colitis.
Chen, J., et al. (2021). Cognitive-behavioral therapy for IBD: A meta-analysis of randomized controlled trials. Inflamm Bowel Dis.
Gracie, D. J., & Ford, A. C. (2017). IBD in remission and functional symptoms: a systematic review. Gastroenterology.
Keefer, L., et al. (2013). Hypnotherapy for IBD: Mechanisms and outcomes. Am J Gastroenterol.
Mawdsley, J. E., et al. (2008). Hypnotherapy and inflammatory cytokines in ulcerative colitis. Gut.
Petrik, M. L., et al. (2024). Post-traumatic stress in IBD: prevalence and treatment. Dig Dis Sci.
Rome Foundation. (n.d.). Understanding Disorders of Gut-Brain Interaction. https://theromefoundation.org/
Sweeney, L., et al. (2021). CBT and health outcomes in youth with IBD. J Pediatr Psychol.