Review for 10.1186/s12876-023-02941-x (2023)

Reviewer’s report
Title: 
BEHAVIOUR REGULATION AND THE ROLE OF MENTAL
HEALTH IN NON-ALCOHOLIC FATTY LIVER DISEASE
Version: 
4 
Date: 
27 Mar 2023
Reviewer's report:
PEER REVIEWER ASSESSMENTS: 
OBJECTIVE - Full research articles: is there a clear objective that addresses one
or several testable research questions? (Brief or other article types: is there a
clear objective?)
Yes - there is a clear objective
DESIGN - Is the current approach (including controls and analysis protocols)
appropriate for the objective?
No - there are major issues
EXECUTION - Are the experiments and analyses performed with sufficient
technical rigor to allow confidence in the results?
Yes - experiments and analyses were performed appropriately
STATISTICS - Is the use of statistics in the manuscript appropriate?
Yes - appropriate statistical analyses have been used in the study
INTERPRETATION - Is the current interpretation/discussion of the results
reasonable and not overstated?
No - there are major issues
OVERALL MANUSCRIPT POTENTIAL - Has the author addressed your
concerns sufficiently for you to now recommend the work as a technically sound
contribution? If not, can further revisions be made to make the work technically
sound?
No - manuscript has some fundamental flaw(s)
PEER REVIEWER COMMENTS: 
GENERAL COMMENTS: The authors have responded adequately to one of the
concerns that I had raised and they have acknowledged that some of the patients
included in "non-lifestyle liver disease" may have liver disease due to their
lifestyle and thus they have renamed this group to "non-NAFLD liver disease
group". It is still an heterogeneous group and thus I am unsure about its
suitability as a control. Authors have not, however, controlled for obesity and I
still believe that this is a problem for the manuscript. Authors indeed state in the
response to reviewers form, in order to explain why it is not that relevant to have
obesity controlled, that "Importantly on this point is the direction of causality
within our study." But the point, precisely, is that we cannot be sure of casuality
in observational studies. That is why we have to control for potential
confounding factors in order to avoid spurious association. This is also in
contrast with this sentence of the manuscript "However, this proposed link has
two caveats.
First, the directionality of the relationship is unknown, as mental health problems
can result
from physical health issues. Secondly, the relationship between NAFLD and PDs
has only
been shown within a cross-sectional methodology at this stage and longitudinal
research would
be required to determine causality."
So, authors should control obesity the same way as they control alcohol use since
this substance is a common cause of liver disease. In addition to this, authors
mention the relevance of obesity in the introduction section but it is not further
mentioned.
REQUESTED REVISIONS: 
Authors should control the presence of obesity and adjust statistical analysis
according to that, since it is a well known factor associated with NAFLD and
also with some personality traits. In case that this is not possible, it should be
added as a major limitation in the discussion section.
Declaration of competing interests
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content of the manuscript?
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Have you received reimbursements, fees, funding, or salary from an
organization that holds or has applied for patents relating to the content of
the manuscript?
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Do you have any other financial competing interests?
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Do you have any non-financial competing interests in relation to this
paper?
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interests' below. If your reply is yes to any, please give details below.
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recommendation.
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Is the study design appropriate to answer the research question (including the use
of appropriate controls), and are the conclusions supported by the evidence
presented?
No
Are the methods sufficiently described to allow the study to be repeated?
No
Is the use of statistics and treatment of uncertainties appropriate?
Yes
Is the presentation of the work clear?
Yes
Are the images in this manuscript (including electrophoretic gels and blots) free
from apparent manipulation?
Yes
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No