1. State your health outcome of interest. (It could be the one you used for week #2 or another one.) Pick two key behaviors that are important factors leading to your health outcome. Explain the importance of these behaviors either for etiology, prevention, or intervention. (If none of the behaviors in the readings are important for your health outcome, suggest another behavior that is.)
Health outcome of interest: Depression
Exercise: Physical activity has been shown to be associated with decreased symptoms of depression in a number of studies. Conversely, physical inactivity is associated with developing psychological disorders, with some studies showing a direct relationship between physical inactivity and symptoms of depression. As such, there have been a number of RCTs that have examined the role of exercise as treatment for depression, with the majority suggesting that exercise is an effective treatment1. When used in combination with antidepressants, exercise has been shown to have improve depressive symptoms1. In fact, in the case of mild to moderate depression, exercise is more favorable than anti-depressants as first-line treatment1.
Diet Quality: In the last decade, many studies have examined and found evidence to support an association between diet quality in the risk for depression, where healthy diets (including fruits, vegetables, fish, nuts, legumes etc.) confer a protective effect against depression and conversely where unhealthy diets (high in processed and/or sugary foods) may increase the risk for depression2-3. A recent systematic review of RCTs that examined dietary interventions with depression and/or anxiety as outcomes found that some evidence for dietary interventions in improving depression outcomes3. However, since this is relationship between diet quality and depression is a relatively new finding, further research regarding this association is required to see if there is indeed a causal effect of diet on the risk of developing depression. In particular, there should be more trials testing the effectiveness of healthy diets as prevention or intervention for depression before we can reach an informative conclusion.
1. Carek, P. J., Laibstain, S. E., & Carek, S. M. (2011). Exercise for the Treatment of Depression and Anxiety. The International Journal of Psychiatry in Medicine, 41(1), 15–28. https://ucsf.idm.oclc.org/login?url=https://doi.org/10.2190/PM.41.1.c
2. Khalid, S., Williams, C. M., Reynolds, S. A. (2016). Is there an association between diet and depression in children and adolescents? A systematic review. British journal of nutrition, 116(12), 2097-2108.
3. Opie, R. S., O'Neil, A., Itsiopoulos, C., & Jacka, F. N. (2015). The impact of whole-of-diet interventions on depression and anxiety: a systematic review of randomised controlled trials. Public health nutrition (Wallingford), 18(11), 2074-2093.
2. Describe how you would study the role of one of the behaviors described for question #1 and your health outcome of interest. Incorporate a social factor (e.g. race/ethnicity, social exclusion, stress) in the study approach.
We can conduct a retrospective case-control study to determine whether diet quality is associated with the risk of developing depression. We could do this by obtaining a large diverse cohort (with varying levels of SES); identifying the depression cases and randomly selecting the controls; and evaluating their general current and past diet quality via surveys. We would then examine whether there is a relationship between diet quality and depression. In addition, we would stratify the results by income and race/ethnicity to see how the association differs among the different strata (eg. high income and white (non-Latino) vs. low income and black) and whether income and race/ethnicity are confounding factors. Limitations of this study include recall bias when answering the survey and the difficulties in methodologically quantifying and measuring diet quality. However, case-control studies would not take as much time as cohort studies because we would not have to wait for the depression diagnoses to occur during our study period.
3. If key health behaviors (e.g. smoking, exercise, nutritious diet) are strongly influenced by neighborhood, income, and/or education, do we need to continue to study how these behaviors influence health outcomes? Why or why not?
Yes, we should still continue to study how these behaviors influence health outcomes because even if they are strongly influenced by neighborhood, income, and/or education, we can still try to develop interventions and policies targeting these behaviours at the community level, specifically in low SES groups. Of course, the ideal scenario would be to have interventions targeting the health disparities at the social level (eg. poverty, education, etc). However, simply relying on that and ignoring health behaviours altogether is not the solution.