The authors reviewed all known English-language literature on the
association between psychiatric factors and ulcerative colitis to ascertain
the evidence for such an association and evaluate the methods used in these
studies. Most of the 138 studies contained serious flaws in research
design, such as lack of control subjects, unspecified manner of data
collection, and absence of diagnostic criteria. Analysis revealed that
methodological flaws were significantly related to the finding of a
positive association between psychiatric factors and ulcerative colitis.
Seven studies represented solid systematic investigation, and all seven
failed to find such an association.