The pathways of mutual influencing between the gut and the brain are strong, and the ‘next wave of research” may involve deliberate microbial interventions as mental health treatments, according to a review of the scientific literature published in the Australian and New Zealand Journal of Psychiatry.
The Australian researchers did a narrative review and found that, “Population surveys show a strong correlation between anxiety, depression, and functional gastrointestinal disorders, contradicting early suspicions that the high prevalence of anxiety and depression in the clinic was mainly due to neurotic health seeking behaviour.”
They also found that this influence was bidirectional and operated through a variety of distinct biological pathways. “Five and 12 year follow-up shows that psychological distress can predict later onset of a functional gastrointestinal disorder and vice versa,” they wrote.
Observations in animal studies suggested that these relationships could potentially lead to effective interventions. “The ability to control rodent temperament and HPA responsiveness with early modification of gastrointestinal flora, and the effects of early stress on the barrier function of the gastrointestinal tract and flora, suggests an ability of both systems to prime each other in early life for later problems,” they wrote. “This hypothesis seems to be supported by a possible protective effect of a probiotic strain of bacteria in a model of early rat psychological trauma.”
Keightley, Philip C., Natasha A. Koloski, and Nicholas J. Talley. “Pathways in Gut-Brain Communication: Evidence for Distinct Gut-to-Brain and Brain-to-Gut Syndromes.” Australian and New Zealand Journal of Psychiatry 49, no. 3 (March 1, 2015): 207–14. doi:10.1177/0004867415569801. (Abstract)