Research Design, Essay Example

The research article I selected examined the relationship between obesity and depression.The author examined the putative link between obesity and depression through data analysis. In particular, the data sample consisted of 3,599 non-pregnant adults (20 years or older) from the National Health and Nutrition Examination Survey.The author measured obesity as a function of an individual’s BMI and waist circumference measures; depression was measured via PHQ-9 scores.

The author used a logistical regression model (coding depression as “1” versus “0”) in order to explore the relationship.Overall, the study found that among individuals with large waist circumference (greater than 88 cm for women and 102 cm for men) and class III obesity (BMI>40), women had a higher prevalence of depression.This finding, however, was not robust; after the author controlled for several demographic variables in the analysis, the association attenuated towards the null.

A majority of the studies addressing this research question, including this one, analyze correlations in observational data.This is not strange: due to the nature of the research question, it would certainly not be ethical for investigators to create a randomized experiment in which one group was given unlimited food (and not allowed to exercise) in order to see the results versus a control group. I don’t believe that the findings from this article can be easily implemented in practice for three reasons.First, there are clearly issues with effect modification among different populations: The inclusion of demographic control variables showed a varying impact on the effect of depression meaning different factors are at play.Second, depression is notoriously hard to diagnosis: In this study, a survey was used to treat individuals with “depression” versus without “depression”.However, it’s not clear how individuals were treated that were depressed at other times or that was not actually covered in the survey at all.Finally, this study only can assess correlations between obesity and depression without assessing the relationship in a causal way.

Sources:

Keddie, A.Associations between severe obesity and depression: results from the national health and nutrition examination survey. Prevention of Chronic Disease, 8(3), 57.