IBD and Crohn’s are 2.18 times more likely to have anxiety disorders . It is also the case for CFS
People will allergies are 2x more likely to develop CFS 
“More symptoms were experienced after the fatigue onset than prior to the fatigue onset; however, a considerable number of participants reported experiencing persisting symptoms prior to the onset of CFS. Particularly, rates of hay fever and asthma were higher prior to the illness” 
” Taken together, our results introduce cellulose as a novel physiological factor that impacts host-bacterial-environmental interactions and alters the proinflammatory potential of AIEC.” . Cellulose food includes:
Volatile organic compounds (VOCs) in breath has been found to be a good predictor of disease state with Crohn’s . It is likely similar results would be seen with CFS and IBS – but studies need to be done.
“The traditional management of Crohn’s disease, which is based on progressive, step-wise treatment intensification with re-evaluation of response according to symptoms, does not improve long-term outcomes of Crohn’s disease and places patients at risk for bowel damage.”  This is likely also true for IBS and CFS.
“The clinical phenotype of the men with CFS (compared to women) was young, single, skilled worker, and infection as the main triggering agent. Men had less pain and less muscle and immune symptoms, fewer comorbid phenomena, and a better quality of life.”
” Cases of CFS had significantly elevated concentrations of transforming growth factor-beta (TGF-β) in five out of eight (63%) studies. No other cytokines were present in abnormal concentrations in the majority of studies, although insufficient data were available for some cytokines. Following physical exercise there were no differences in circulating cytokine levels between cases and controls and exercise made no difference to already elevated TGF-β concentrations. The finding of elevated TGF-β concentration, at biologically relevant levels, needs further exploration, but circulating cytokines do not seem to explain the core characteristic of post-exertional fatigue.” 
“Neuroimage may be an important key to unveil the central nervous system (CNS) mechanism in CFS. Although most of the studies found gray matter (GM) volumes reduced in some brain regions in CFS,”
” It has been shown that the time it takes to process a complex cognitive task, rather than error rate, may be the critical variable underlying CFS patients’ cognitive complaints.”