Psychiatric and mood disorders may play an important role in the development and persis-
tence of irritable bowel syndrome (IBS). Previously, we hypothesized that stress-induced implicit
memories may persist throughout life via epigenetic processes in the enteric nervous system (ENS),
independent of the central nervous system (CNS). These epigenetic memories in the ENS may con-
tribute to developing and perpetuating IBS. Here, we further elaborate on our earlier hypothesis. That
is, during pregnancy, maternal prenatal stresses perturb the HPA axis and increase circulating cortisol
levels, which can affect the maternal gut microbiota. Maternal cortisol can cross the placental barrier
and increase cortisol-circulating levels in the fetus. This leads to dysregulation of the HPA axis, affect-
ing the gut microbiota, microbial metabolites, and intestinal permeability in the fetus. Microbial me-
tabolites, such as short-chain fatty acids (which also regulate the development of fetal ENS), can mod-
ulate a range of diseases by inducing epigenetic changes. These mentioned processes suggest that
stress-related, implicit, long-term epigenetic memories may be programmed into the fetal ENS during
pregnancy. Subsequently, this implicit epigenetic stress information from the fetal ENS could be con-
veyed to the CNS through the bidirectional microbiota-gut-brain axis (MGBA), leading to perturbed
functional connectivity among various brain networks and the dysregulation of affective and pain pro-