"Specifically IBS, IBD, and GERD?"
The endocannabinoid system (ECS) is largely devoted to maintaining homeostasis (the tendency of organisms to auto-regulate and maintain their internal environment at equilibrium). Deficiency or malfunction of the ECS has become a focus for researchers seeking treatment options for several maladies—especially those that have few, if any, effective pharmocotherapeutic interventions, such as celiac disease, MS, fibromyalgia, IBD and IBS. In fact, the scientific community has recently termed the ECS malfunction: Clinical Endocannabanoid Decifiency, or CEDC. CBD works by balancing and supporting the ECS through its subtle effects on cannaboinoid receptor-1 (CB1) and cannaboinoid receptor-2 (CB2) receptors, as well as other receptors that modulate serotonin, GABA, dopamine, and many more.
In IBD and GERD, inflammation is central to both the etiology and symptomology of the respective disease. CBD is well known as an effective immunomodulator and anti-inflammatory, and those properties still do apply to GI inflammation. However, unique to the GI tract, are specialized nerve cells called enteric glial cells— "the glue of the nteric nervous system (ENS)"—which, when overactive, also contribute to acute and chronic GI inflammation. Recent pre-clinical research suggests that CBD may lower GI inflammation by controlling reactive gliosis in the ENS. Or, in other words, CBD restores homeostasis in the gut by reducing hyperactivity in enteric glial cells.
The ENS is an extensive network of neurons supported by enteric glial cells (the above mentioned "glue" on the ENS). Two neural plexuses comprise the ENS: the myenteric plexus, involved in motility/peristalsis; and the submucosal plexus, involved in intestinal and gastric secretions. CBD works to restores homeostasis in the ENS via modulation of enteric glial cells (as mentioned above), the myenteric plexus, and the submucosal plexus.
Although inflammation plays little, if any, role in the pathology of IBS, CBD’s balancing of the myenteric plexus lessens inappropriate and painful intestinal contractions; while balancing of the submucosal plexus reduces inappropriate gastric and intestinal secretions. CBD’s effects on glial cells, the submucosal plexus and myenteric plexus factor into CBD’s ability to alleviate symptoms of GERD, IBS and IBD.
An ongoing, randomized, placebo controlled, double-blind, cross-over trial has shown chewable CBD to significantly reduce IBS-related pain. To be included in the study, it was also necessary that patients experienced, according to their own account, at least three pain episodes per week of a predefined intensity. All patients who participated in the study experienced decrease in their levels of pain score. On top of the overall reduction, the trend curve suggests 50% higher pain reduction.
Furthermore, several studies show that among patients who seek medical attention for IBS or IBD, around 70% of IBS patients, and 30% of IBD patients, have psychiatric comorbidity—depression and generalized anxiety disorder being most common. CBD increases serotonin signaling at the 5-HT1A receptor—the same neurotransmitter and receptor that SSRIs like Prozac influence—which is mostly why CBD has antidepressant and anxiolytic properties. In fact, SSRIs and tricyclic antidepressants (which also increase serotonin signalling), have been shown to alleviate anxiety and depression symptoms, as well as alleviate some of the abdominal pain and bowel symptoms involved in IBS, IBD and gastroesophageal reflux disease (GERD), which is why SSRIs and TCAs are commonly prescribed for IBS and IBD.
I hope this helps!