Gut-to-Brain or Brain-to-Gut axis – terms I hear frequently when supervising student clinic and indeed I use in discussion with my own clients. While there is a common understanding that the brain-gut pathways are bi-directional, recent research indicates it might be important to clarify the impact of this bidirectional pathway. Does the brain have a stronger influence on the gut and creating, for example IBS-like symptoms or is the gut driving our brain, leading to anxiety, depression and mood changes? Importantly, whatever the case, does this impact on how we manage treatment?
Given the significant association with psychological conditions such as depression and anxiety, thinking has been that functional gastrointestinal disorders such as irritable bowel syndrome (IBS) and functional dyspepsia (FD) have originated in the brain and are modulated by stress pathways. That is, our thoughts and emotions drive physical stress responses, which then impact in various ways on our gut (brain to gut). However, there are inconsistencies with this understanding. For example the significant association between gastrointestinal infection and subsequent IBS points to at least a proportion of people have symptoms that originate in their gut, which can then impact on mood, leading to anxiety or depression.
Last year Australian researchers set out to determine how many people with IBS and FD have symptoms that originate in their gut (gut-to-brain) compared to those where symptoms first originated from psychological input (brain-to-gut). Findings showed that even though the pathway is bidirectional, “a major subset begin with gut symptoms first and only then psychological distress develops”, indicating that gut mechanisms are in many cases the primary starting point and cause of the gut and psychological symptoms (Koloksi, et al, 2016). The research showed that while the brain-to-gut pathway is relevant, the gut-to-brain pathway may in fact predominate and should not be overlooked during treatment planning.
Why is this important? From a naturopathic view, treatment is holistic however; the order of disease onset is significant when formulating a treatment plan. For those with a predominant brain-to-gut pathway centrally focused approaches along with psychological and mindfulness might feature strongly. Alternatively, those with a predominant gut-to-brain pathway, for example IBS that started with a gastrointestinal infection, may respond better to a focus on gut-directed interventions, with central/mood-focused approaches as supportive therapy.
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Koloski, N.A., Jones, M. and Talley, N.J., 2016. Evidence that independent gut‐to‐brain and brain‐to‐gut pathways operate in the irritable bowel syndrome and functional dyspepsia: a 1‐year population‐based prospective study. Alimentary Pharmacology & Therapeutics, 44(6), pp.592-600.