I can definitely attest to the theory that sometimes anxiety in CFS/ME is related to intestinal dysbiosis. There are several gut-brain connection paths (vagus nerve link, nitric oxide signaling, cytokines), and it turns out that gut infection and inflammation can have a knock-on effect, and kick off brain inflammation (Ref). Brain inflammation has powerful and deleterious effect on mood, and can give rise to anxiety and depression symptoms. Once I started taking generous doses of PREBIOTICS (rather than probiotics) to fix my gut dysbiosis, within a week or so, my anxiety symptoms were vastly improved. Some info on the use of PREBIOTICS to soothe gut dysbiosis/inflammation is here: The Wonders of Prebiotics. If you are going to try this prebiotic protocol, please use high doses of more than one type of prebiotic, two or three times a day. This makes all the difference. Probiotics may be useful too, but I thing they are not as important as prebiotics. At least, that is what I discovered. I hope this prebiotics protocol helps others fix their anxiety/depression as much as it helped fix my mental miseries.