Chronic Fatigue Syndrome: Whitehead WE

Whitehead WE. · No affiliation provided · Am J Gastroenterol. · Pubmed #17897338 No free full text.

Abstract: Twin studies have traditionally been used to assess the heritability of diseases such as irritable bowel syndrome (IBS) by comparing concordance rates in monozygotic twins (identical genetic endowment) to dizygotic twins (half of genes shared). Wojczynski et al. used twins in a novel way-they studied monozygotic twins who were discordant for IBS (but who shared identical genes) to show that the comorbidity of IBS with major depressive disorder could NOT be due to genetic influences. This paradigm provides the most rigorous method for separating genetic from environmental influences and should be adopted by other researchers. However, the authors' conclusion that major depressive disorder and IBS are part of the same pathophysiological process is questioned on the basis of (a) incomplete co-occurrence of IBS and major depressive disorder (13-45% co-occurrence) and (b) lack of specificity-the authors show that chronic widespread pain (related to fibromyalgia) and chronic fatigue are also strongly associated with IBS. This study provides precise, generalizable estimates from a large population-based study for the comorbidity of IBS with major depressive disorder, chronic widespread pain, and chronic fatigue.

Whitehead WE, Palsson O, Jones KR. · Division of Digestive Diseases and Center for Functional Gastrointestinal and Motility Disorders, University of North Carolina, Chapel Hill, North Carolina 27599, USA. · Gastroenterology. · Pubmed #11910364 No free full text.

Abstract: BACKGROUND & AIMS: Comorbid or extraintestinal symptoms occur frequently with irritable bowel syndrome and account for up to three fourths of excess health care visits. This challenges the assumption that irritable bowel is a distinct disorder. The aims of this study were to (1) assess comorbidity in 3 areas: gastrointestinal disorders, psychiatric disorders, and nongastrointestinal somatic disorders; and (2) evaluate explanatory hypotheses. METHODS: The scientific literature since 1966 in all languages cited in Medline was systematically reviewed. RESULTS: Comorbidity with other functional gastrointestinal disorders is high and may be caused by shared pathophysiological mechanisms such as visceral hypersensitivity. Psychiatric disorders, especially major depression, anxiety, and somatoform disorders, occur in up to 94%. The nongastrointestinal nonpsychiatric disorders with the best-documented association are fibromyalgia (median of 49% have IBS), chronic fatigue syndrome (51%), temporomandibular joint disorder (64%), and chronic pelvic pain (50%). CONCLUSIONS: Multivariate statistical analyses suggest that these are distinct disorders and not manifestations of a common somatization disorder, but their strong comorbidity suggests a common feature important to their expression, which is most likely psychological. Some models explain the comorbidity of irritable bowel with other disorders by suggesting that each disorder is the manifestation of varying combinations of interacting physiological and psychological factors. An alternative hypothesis is that the irritable bowel diagnosis is applied to a heterogeneous group of patients, some of whom have a predominantly psychological etiology, whereas others have a predominantly biological etiology, and that the presence of multiple comorbid disorders is a marker for psychological influences on etiology.