Review for 10.1186/1471-230X-10-88 (2010)

Reviewer's report
Title:Prevalence of mood and anxiety disorder in self reported irritable bowel
syndrome (IBS). An epidemiological population based study of women
Version: 1Date:10 May 2010
Reviewer: Vladeta Ajdacic-Gross
Reviewer's report:
This is an interesting epidemiological paper on the association between mood
and anxiety disorders and IBS. The data came from a medium sized
epidemiological survey with a sample size with some more than 1000 (female)
participants. The analysis was well designed with respect to the state of the
research and included extensions to differentiate the results (current vs. lifetime
occurrence of psychiatric diagnoses and IBS; comparison of IBS with diabetes
and hypertension; exploratory analysis with specific psychiatric diagnoses). A
critical reading of the manuscript revealed a few major and several minor
suggestions.
Major issues:
• The manuscript did not explain why this study is based merely on a sample of
women. To my understanding, the Geelong Osteoporosis Study includes males
and females. On page 16, last paragraph, the authors remarked that the
"inclusion of women only obviously restricts the generalisability of our findings".
In fact, diverging findings in men and women might provide new clues to a better
understanding of diseases which burden women more than men.
• In contrast to the analysis design, the interpretation of the results appears to be
quite unidimensional. Firstly, it misses that not only psychiatric disorders but also
IBS may represent heterogenous conditions. Secondly, the interpretation does
not consider that there are hypothetically several different interrelations and
causal paths, which may coexist. This may be due to the heterogeneity of the
diseases, but also to different temporal sequence patterns. To my opinion, the
conclusions are somewhat rash. I also wondered that the authors did not include
hypotheses, which might be derived from their recent paper on nutrition and
affective disorders (Felice N. Jacka et al.: Association of Western and Traditional
Diets With Depression and Anxiety in Women. Am J Psychiatry 2010; 167:1–7).
Minor issues:
• The sample of this study is larger than in most other studies examining IBS and
psychiatric disorders. However, with respect to the hetorogeneity of these
diseases even much larger samples would be needed. Thus, this study is now
midway.
• The paragraph on page 5/6 ("Despite many studies ...") was difficult to read and
might need some reworking: a) the studies with negative results were quoted
twice; b) the sentence next to last introduced a fourth issue (or should
alternatively be moved to the second issue two)
• Dose-response relationship (page 14, paragraph 14): I guess that a nested
model (differentiating the subgroups 1-3 vs. 4) would work at least as well as a
linear or curvilinear relationship. Thus, the analysis paves the way for two quite
different interpretations.
• The exceptional finding, that there was no association between IBS and bipolar
disorder might turn out to be revealing in future studies and thus deserves
eventually some more emphasis in the Discussion.
• Association of IBS and GHQ-12 (page 17): from a methodological point of view,
this association is not surprising. It might be explained by the fact that summary
scores often work better than specific variables in association analyses.
• Page 18, paragraph 3: This paragraph is misplaced between paragraphs
discussing the associations. Eventually, it could be omitted.
• Table 1:
The first row has no labels and no overall figures in the first row. Please indicate
also that the %-values pertain to the rows.
• Table 3:
The first row has no labels. Please indicate also that the %-values pertain to the
rows.
• Table 3:
The title announces "lifetime IBS, hypertension and diabetes" but only the IBS
figures were shown. Please provide the lacking figures.
• Tables 4 and 5:
To what do the %-values pertain?
Level of interest: An article of importance in its field
Quality of written English: Acceptable
Statistical review: No, the manuscript does not need to be seen by a
statistician.
Declaration of competing interests:
I declare that I have no competing interests.