Critical Appraisal Essay: Analyzing Epidemiological Studies, PUBH6005

This essay critically appraises three epidemiological studies examining the relationship between obesity and depression in adolescents and young adults. The studies include a cross-sectional study, a case-control study, and a longitudinal/cohort study. The essay uses the CASP (Critical Appraisal Skills Programme) checklist to evaluate each study's methodology, including participant selection, exposure and outcome measurement, confounding factors, and statistical analysis. The essay highlights the strengths and weaknesses of each study, assessing their validity, reliability, and potential biases. It also examines the study findings, including the association between obesity and depression, and their implications for public health practice. The author synthesizes the evidence to determine the credibility and applicability of the results, considering the limitations of each study design. The essay concludes with a discussion of the implications of these findings for understanding and addressing the co-occurrence of obesity and depression, and the need for further research to clarify the relationship between these two conditions.

Running head: CASP ESSAY 1
CASP ESSAY
Name
Institutional Affiliation

CASP 2
PART A
Zhao, Z., Ding, N., Song, S., Liu, Y., & Wen, D. (2019). Association between depression and
overweight in Chinese adolescents: a cross-sectional study. BMJ Open, 9(2), e024177. Retrieved
from: https://bmjopen.bmj.com/content/9/2/e024177
Table 1. Cross-Sectional Study CASP Checklist
No. Questions ANS. Comment
1. Were the criteria for inclusion in
the sample clearly defined?
Yes The criteria for inclusion was clearly defined by the
researchers.
2. Were the study subjects and the
setting described in detail?
Yes Subjectivity and the setting study have been well
elaborated.
3. Was the exposure measured
validly and reliably?
Yes Notably, the study exposure validity was measured in a
reliable and compelling manner.
4. Were the objectives, standards,
and criteria used for the
measurement of the condition?
Can’t
tell
It is not exclusively whether standard perimeters for
measurement.
5. We’re confounding factors
identified?
Yes Confounding variables such as age, sex have been
acknowledged
6. Were strategies to deal with
confounding factors stated?
Yes. Multiple imputation techniques was used to control the
confounding variables.
7. Were the outcomes measured Yes The outcome measurement validity and reliability was

CASP 3
validly and reliably? measured through crude and odd ratios.
8 Was an appropriate statistical
analysis used?
Yes Stata version 13 was used as an appropriate statistical
analysis tool for the study.
Y = YES, N = NO, NC = NOT CLEAR
Koski, M., & Naukkarinen, H. (2017). The relationship between depression and severe obesity: a
case-control study. Open Journal of Psychiatry, 7(04), 276. Retrieved from:
https://m.scirp.org/papers/78536
Table Two: Case-Controlled Study CASP Checklist
NO. Question ANS. Comments
1. Did the study address a focused
issue?
Yes The study investigated and provided
information on the study problem.
2. Did the author use an appropriate
method to answer their question?
Yes Appropriate method was used to respond to the
survey of significant concern.
3. Were the case recruited acceptably? Yes The recruitment was done in a legal and
acceptable procedure.
4. Were the controls selected
acceptably?
Yes A matched control approach was employed
5. Was the exposure accurately
measured to minimize bias?
Yes Exposure was accurately measured using the
P-values.

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6. (a) Aside from the experimental
intervention, were the groups
treated equally?
(b) Have the authors take account
of the potential confounding
factors in the design and their
analysis?
Yes There were minimum biasness, and all the
treatment of study groups was based on equally
apart from the interventions.
Moreover, adjustments was used to minimize
the confounder factors.
7. How significant was the treatment
effect?
The treatment effect was large enough
8. How precise was the estimate of the
treatment effect?
The study treatment can be gauged as an
averagely precise study.
9. Do you believe the results? NO the study results are believable based on
various reasons.
10. Can the results be applied to the local
population?
No This study cannot be used in the community.
11. Do the results of this study fit with
other available evidence?
NO The study result was not consistent
Y = YES, N = NO, NC = NOT CLEAR
Herva, A., Laitinen, J., Miettunen, J., Veijola, J., Karvonen, J. T., Läksy, K., & Joukamaa, M.
(2006). Obesity and depression: results from the longitudinal Northern Finland 1966 Birth

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Cohort Study. International journal of obesity, 30(3), 520. Retrieved from:
https://www.nature.com/articles/0803174
Table three: longitudinal or cohort study
No. Questions ANS. Comments
1 Did the study address a focused issue? YES The study elaborately examined
obesity and depression which was
the main issue.
2 Was the cohort recruited acceptably?
Is it worth continuing?
YES The study cohort recruitment was
done in an acceptable manner
focusing only people between ages
14-31.
3 Was the exposure accurately measured
to minimize bias?
YES Accurate BMI body measurement,
and HSCL was also used to measure
accuracy.
4 Was the outcome accurately measured
to minimize bias?
YES The result of the study was precisely
measured using the OR, CI, and the
HSCL- 25.
5 (a) Have the authors identified all-
important confounding
factors?
(b) Have they take account of the
confounding factors in the
design and analysis?
Various confounders were identified
and accounted for in the study
design.

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6 (a) Was the follow up of subjects
complete enough?
(b) Was the follow up of subjects
long enough?
YES The subject follows up was long and
complete enough as all 7513
participants were returned the
questionnaires.
7 What are the results of this study? The results shown that female
adolescent was at a higher risk of
getting depression
Young adults with obesity were at a
higher risk of depression.
8
How precise are the results? The study is precise with a
regression value of 95%.
9 Do you believe the results? Yes The results of the study are
believable
10
Can the results be applied to the local
population?
YES The public can use the result of this
study.
11 Do the results of this study fit with
other available evidence?
YES The study results fit the existing
evidence such as the physician
diagnosis.
12 What are the implications of this study
for practice?
The study shows the depression and
obesity prevalence, which is
essential in epidemiology.

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CASP ESSAY B
Introduction
Evidently from World Health Organization, obesity and overweight have been a
significant concern in the world. The disease has been increasing in prevalence with relatively
9% annually and is associated with other health concerns such as depression and cardiovascular-
related infections. The increasing of the disease prevalence annually among the adolescent has
been noted to as a result of the young adults’ bodies not changing easily. Moreover, it has been
found that there is a close relationship between depression and obesity, leading to the selection of
the topic. Also the CDC data indicates that obesity and depression is high where 18% of the
world young adults. The current study will, therefore, assess and investigate why most
adolescent and youth adults with obesity are likely to suffer from depression.
Methodology:
The methodology involved in the section and finding of the three articles was based on
trial and error method where I used keywords to such on major epidemiology databases of WHO
and BMJ research center. To gets the three articles for the study, I used keywords such as
adolescent, obesity, overweight, depression, Cohort/ longitudinal study, cross-sectional study,
and case-control study. This made it easy to get the most relevant and peer-reviewed articles
relating to the selected study topic. Three related studies were then decided on the same problem
but with different study designs that are cohort study, cross-sectional study, and case-controlled
study (Kneale, Thomas, O'Mara‐Eves & Wiggins, 2019). I then analyzed each study using the
CASP checklist as in section as here below.
Results:
Table 1. Cross-Sectional Study CASP Checklist

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No. Questions ANS. Justification
1. Were the criteria for inclusion in
the sample clearly defined?
Yes The authors of the article drew participants all across
china, where approximately 1081 adolescents from the
Chinese Family Panel Studies were selected as the study
sample. The study combined both female and male
participants suffering from both overweight and depressed
adolescents were obtained CES-D (Zhao et al. 2019).
2. Were the study subjects and the
setting described in detail?
Yes The authors of the study defined subjectively of the study
as well as elaborately illustrated the setting of the study.
As evident from the study design description, the study
subjects were obtained through China Panel Studies, and
the data analysis was at the Chinese epidemiology center.
The data analysis was also done at the center using
epidemiological studies depression scale (CES-D), and all
the participants were of ages 10-17 years.
3. Was the exposure measured
validly and reliably?
Yes Notably, the study exposure validity was measured in a
reliable as well as a compelling manner based on both
validity and reliability measures. Taking, for example,
individual characteristic could trigger exposure were
adequately measure through RO, P, and CI values.
4. Were the objectives, standards,
and criteria used for the
Can’t
tell
However, it is not entirely clear from the mere look of the
study as to whether standard perimeters for measurement

CASP 9
measurement of the condition? were highlighted anywhere within the study. Thus, they
cannot tell the answer.
5. We’re confounding factors
identified?
Yes The authors of the study mention various confounding
variables such as age, sex, an area where a subject was
from as well as maternal height and education. These
variables appeared to be standalone but could affect the
outcome of the study without control measures.
6. Were strategies to deal with
confounding factors stated?
Yes. The most evident from the analysis of the study is
carrying out of multiple imputation techniques to control
the confounding variables.
7. Were the outcomes measured
validly and reliably?
Yes The outcome measurement validity and reliability was
balanced and adjusted through the use of crude and odd
ratios. The CI was retained ta 95% and p-value of <5 was
used for moderation (Kim, Sefcik & Bradway, 2017).
8 Was an appropriate statistical
analysis used?
Yes The appropriate statistical analysis was done by the
researchers where all the available data were analyzed
using Stata version 13. Therefore, the researchers used
BMI values for the general subjects, t-test for
interdependent samples, Pearson’s χ2 test was used to
analyze categorical data and finally the study used CES-D
fir binary data or variables (Zhao et al. 2019).

CASP 10
Table Two: Case-Controlled Study CASP Checklist
NO. Question ANS. Justification
1. Did the study address a focused
issue?
Yes The study investigated and provided
information on the relationship between
depression and obesity among various age
groups. In as much as the answer was not direct
to an adolescent, it answered the question
(Koski & Naukkarinen, 2017).
2. Did the author use an appropriate
method to answer their question?
Yes The authors of the study employed an
appropriate method to answer the survey of
significant concern. The study authors used a
multicenter method with 131 individuals who
were evaluated and studies to achieve the study
outcome.
3. Were the case recruited acceptably? Yes It is agreeable that the recruitment was done in
a legal and acceptable procedure. Both
adolescents and adults were obtained through
obesity and disability pension and healthcare
plan. All the 131 participants met with the
researches, and their consents were taken
before the commencement of the study.
4. Were the controls selected Yes The controls were selected in an acceptable

CASP 11
acceptably? manner where he studies employed a matched
control approach. This selection was to ensure;
inclusion, replacement of missing commands,
and to ensure that the study group remained
within the required limit (Koski &
Naukkarinen, 2017).
5. Was the exposure accurately
measured to minimize bias?
Yes Patients exposed to the disease to the disease
was accurately measured using the P-values to
ensure that there was limited bias for all the
selected study groups.
6. (c) Aside from the experimental
intervention, were the groups
treated equally?
(d) Have the authors take account
of the potential confounding
factors in the design and their
analysis?
Yes There were minimum biasness, and all the
study groups were treated equally apart from
the interventions. The study shows no signs of
biasness since the study authors considered all
the possible confounding within the study
design and methodology.
Moreover, the authors of the study came up
with adjustments for the confounding factors
such as age, sex, and education.
7. How significant was the treatment
effect?
Based on the results, it can be noted that the
treatment effect was large enough, and the
relationship between obesity and stress
tolerance as per the p-value stood at (p =

CASP 12
0.030).
8. How precise was the estimate of the
treatment effect?
Based on the p-value consistency, the study
treatment can be gauged as a precise study.
9. Do you believe the results? NO I don't believe he results if the study as its
findings indicate that there is no relationship
between obesity and depression among people
of various ages. This is because many other
studies done on the same topic have confirmed
an existing relationship between the two
medical problems.
10. Can the results be applied to the local
population?
No The result of this study indicates limited
clinical effects thus cannot be used in the
community. Moreover, the study findings are
out of context, meaning no existing relationship
between obesity and depression.
11. Do the results of this study fit with
other available evidence?
NO The study result was not consisted of where its
findings only confirmed with one Canadian
study on the same topic (Kim, Sefcik &
Bradway, 2017). Nonetheless, the study results
contradicted other studies on the same problem
as most of the scholars dealing with the same
topic of research have found an existing

CASP 13
relationship between obesity and depression.
This has also been indicated as a weakness in
the study.
Table three: longitudinal or cohort study
No. Questions ANS. Justification/ Results
1 Did the study address a focused issue? YES The study addressed a fixated topic
where it inspected the existing
connotation between body size and
depression using a precise
longitudinal study setting to
determine the study problem (Herva
et al. 2006).
2 Was the cohort recruited acceptably?
Is it worth continuing?
YES The study cohort was recruited in an
acceptable manner focusing only
people between ages 14-31 years in
Northern Finland, and the cohort
data was obtained legally through
postal inquiry.
All the 8451 study subjects gave
written consent as well as their
health status information (Herva et

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al. 2006). Therefore, the study is
worth continuing.
3 Was the exposure accurately measured
to minimize bias?
YES Author of the study employed
accurate BMI body measurement,
and HSCL was also used to measure
accuracy regarding the selected
subjects' conditions. Odd ration OR
was also applied to identify the
cutoff mark to minimize bias.
4 Was the outcome accurately measured
to minimize bias?
YES The outcome of the study was
accurately measured using the OR,
CI, and the HSCL- 25. The
adjustment ration stood at 1.4, which
was 95% accurate. Such adjustments
help with the elimination of bias as
the cutoff ark was established.
5 (c) Have the authors identified all-
important confounding
factors?
(d) Have they taken account of
the confounding factors in the
design and analysis?
The authors of the study identified
various confounders of the study and
took them into account in the study
design. The identified study
confounding factors included the use
of alcohol, smoking, dietary, father's
social class, and level of education,

CASP 15
marital status and exposure to
chronic somatic disease.
6 (a) Was the follow up of subjects
complete enough?
(b) Was the follow up of subjects
long enough?
YES The subject follows up was long and
complete enough. All the study
participants were alive by the end of
the follow-up, and the authors of the
study were able to access depression
indicators at the age of 31years, and
7513 participants were able to return
the questionnaires.
7 What are the results of this study? The results show that female
adolescent was at a higher risk of
getting depression after a body gain
compared to female subjects who
remained regular, which was 2.17
higher. On the other hand, males
with obesity were 2.07 higher fold
risk of being diagnosed with
depression. Thus found conforming
association between obesity and
depression among adolescents and
young adults.
How precise are the results? The study was reasonably precise
with a regression value of 95% and

CASP 16
8 conformed to the previous studies in
terms of finding and theoretical
analysis.
9 Do you believe the results? Yes The results of the study are
believable; the data analysis was
accurate and relatable to other
previous studies.
10
Can the results be applied to the local
population?
YES The public can use the result of this
study based on its clinical strengths
and contributions.
11 Do the results of this study fit with
other available evidence?
YES The study results fit the existing
evidence such as the physician
diagnosis, and moreover, the study
results are similar and support
previous studies on the same topic
(Kim, Sefcik & Bradway, 2017).
12 What are the implications of this study
for practice?
The study implies that it shows the
depression and obesity prevalence,
which is essential in epidemiology
and clinical evaluation of the
continually growing rate of
depression and obesity (Kim, Sefcik
& Bradway, 2017).

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Discussion:
In as much as the selected studies focused on the same topic of study, the authors used
varied study designs and methodologies. To begin with, the selected cross-sectional and case-
control study had similar confounding factors compared to the cohort (Adams et al. 2015). The
evident cofounding variables included age, sex, the area where a subject was from, maternal
height, and education for the two studies. Longitudinal cohort study, on the other hand also had
various confounder variables such as use of alcohol, smoking, dietary, father’s social class, and
level of education, marital status and exposure to chronic somatic disease (Safdar, Abbo,
Knobloch & Seo, 2016).
Evidently, to solve and eliminate the effect of confounding variables, authors of the
cross-sectional study used multivariable adjustment (Herva et al. 2006). The same strategy was
employed by the authors who used case-control research while the longitudinal cohort study
author used matched control measures. Concerning study group bias, the authors employed
effective strategies such as justified participant cut-offs and the use of characteristic analysis
(LoBiondo-Wood & Haber, 2017). There was no evident study group bias in all the three studies;
thus, the yes reason and justifications in all the three tables. However, there existed several
confounders in all the three studies which can be reduced through the improvement of the
methodologies (Elwood, 2017). The most immediate thing I will add to my study design control
variables within the within-subject designs to eliminate adverse effect or I would employ random
sampling technique which has limited chances for confounder effect. To this manner, future
research should use randomized sampling techniques or add control variables to eliminate bias
(Gray, Grove & Sutherland, 2016).
Conclusion:

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Based on the paper discussion, it can be concluded that various study designs have
multiple features that others do not have. The effectiveness of the study, therefore, depends on
the study design and approaches employed by study authors. Moreover, without proper
evaluation of the confounders in any investigation, there is a likelihood of bias. Therefore, to
eliminate or minimize the effect of these confounders, the researcher must introduce control
variables or use random study technique.
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Outcomes (CaMEO) Study methods and baseline results. Cephalalgia, 35(7), 563-578.
Elwood, M. (2017). Critical appraisal of epidemiological studies and clinical trials. Oxford
University Press.
Gray, J. R., Grove, S. K., & Sutherland, S. (2016). Burns and Grove's The Practice of Nursing
Research-E-Book: Appraisal, Synthesis, and Generation of Evidence. Elsevier Health
Sciences.

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Herva, A., Laitinen, J., Miettunen, J., Veijola, J., Karvonen, J. T., Läksy, K., & Joukamaa, M.
(2006). Obesity and depression: results from the longitudinal Northern Finland 1966
Birth Cohort Study. International journal of obesity, 30(3), 520. Retrieved from:
https://www.nature.com/articles/0803174
Kim, H., Sefcik, J. S., & Bradway, C. (2017). Characteristics of qualitative descriptive studies: a
systematic review. Research in nursing & health, 40(1), 23-42.
Kneale, D., Thomas, J., O'Mara‐Eves, A., & Wiggins, R. (2019). How can additional secondary
data analysis of observational data enhance the generalisability of meta‐analytic evidence
for local public health decision making?. Research synthesis methods, 10(1), 44-56.
Koski, M., & Naukkarinen, H. (2017). The relationship between depression and severe obesity: a
case-control study. Open Journal of Psychiatry, 7(04), 276. Retrieved from:
https://m.scirp.org/papers/78536
LoBiondo-Wood, G., & Haber, J. (2017). Nursing research-E-book: methods and critical
appraisal for evidence-based practice. Elsevier Health Sciences.
Safdar, N., Abbo, L. M., Knobloch, M. J., & Seo, S. K. (2016). Research methods in healthcare
epidemiology: survey and qualitative research. infection control & hospital
epidemiology, 37(11), 1272-1277.
Zhao, Z., Ding, N., Song, S., Liu, Y., & Wen, D. (2019). Association between depression and
overweight in Chinese adolescents: a cross-sectional study. BMJ Open, 9(2), e024177.
Retrieved from: https://bmjopen.bmj.com/content/9/2/e024177

CASP 20