Background: Several studies have shown that patients with functional somatic syndromes (FSS) have. on average. deficient endogenous pain modulation (EPM). as well as elevated levels of negative affectivity (NA) and high comorbidity with depression and reduced resting heart rate variability (HRV) compared to healthy controls (HC). https://hollandscountryclothinges.shop/product-category/digestive-supplements/