A reader wrote me about this herb that was in a mixture that contains several items that I also favor. I was not familiar with it, so I did a little research.
Bacopa monniera is a herb used in Indian Traditional/ “Ayurvedic treatment for epilepsy and asthma. It is also used in Ayurveda for ulcers, tumors, ascites, enlarged spleen, inflammations,leprosy, anemia, and gastroenteritis. ” – Wikipedia
Examine.com writes “Bacopa monnieri is a Nootropic herb that has been used in traditional medicine for longevity and cognitive enhancement. Supplementation can reduce anxiety and improve memory formation.”
There is an excellent narrative on Ayurvedic use of this herb over the last 5500 years.
Many of these areas are known to be associated with microbiome dysfunction. Does modern medical science agree? Over to PubMed which around 160 articles in total. The interesting results are:
- “These results indicate that, cognition-enhancing and neuromodulatory propensity of BME is through modulating the expression of AChE, BDNF, MUS-1, CREB and also by altering the levels of neurotransmitters in hippocampus of rat brain.” 
- ” Studies in animal model evidenced that Bacopa treatment can attenuate dementia and enhances memory. Further, they demonstrate that Bacopa primarily either acts via antioxidant mechanism (i.e., neuroprotection) or alters different neurotransmitters (serotonin (5-hydroxytryptamine, 5-HT), dopamine (DA), acetylcholine (ACh), γ-aminobutyric acid (GABA)) to execute the pharmacological effect. ” 
- “Present study also confirms that 80-120 mg/kg doses of BM extract have significantly higher antidepressant-like activity.”
- “Bacopa monniera ameliorates cognitive impairment and neurodegeneration induced by intracerebroventricular-streptozotocin in rat: behavioral, biochemical, immunohistochemical and histopathological evidences.“
- “The present results clearly demonstrate that the methanolic extract of B. monniera possesses antidepressant-like activity in the animal behavioral models” 
- “treatment with BM extract during growth spurt period of neonatal rats enhances learning and memory”
- “The current study attempted to determine the chronic effects of single daily dose of 450 mg of Brahmi extract on cognitive performance and anxiety in healthy adults. The results of the current study are not in agreement with findings of some of the earlier studies which have found improvement both on cognitive parameters and a reduction of anxiety scores… However, there was a trend for lower state anxiety in the B. monniera (Brahmi) group as compared to placebo group.” 
- ” Promising indications for use in humans include improving cognition in the elderly and in patients with neurodegenerative disorders.” 
- “Promising candidates for future research include Bacopa monniera (brahmi) …providing potential efficacy in improving attentional and hyperkinetic disorders via a combination of cognitive enhancing and sedative effects.” 
Bacteria / Gut
- ” we had reported the prophylactic and curative effects of standardized extract of Bacopa monniera (BME) in various gastric ulcer models. The effect was due to augmentation of the defensive mucosal factors like increase in mucin secretion, life span of mucosal cells and gastric antioxidant effect rather than on the offensive acid-pepsin secretion.” 
- “BME showed antimicrobial activity against skin pathogens,”
- ” a butanolic extract of Bacopa monnieri showed maximum inhibitory activity against the human pathogen Escherichia coli,” 
There are no studies with CFS/FM/IBS patients which would be ideal. My gut feeling (subjective) is that it is worth trying at 500-1000 mg/day. The most likely effect is reduction of the stress response (which usually have side effects of improved cognitive abilities). There is also a potential that it may reduce leaky gut – but that has not been explored or demonstrated in studies.