Though a positive correlation between depression and obesity is well-established, the link between depression and body mass index (BMI) across a range of body sizes is not as clear. Some findings have shown an association between depression and BMI, while others suggest that it only applies in cases of severe obesity.
Noting the need for further research to identify mechanisms underlying this relationship, researchers from several US universities investigated the association between depression and body mass index (BMI). In their new study reported in Obesity Research & Clinical Practice, they used logistic regression to explore the link in a population-based, randomly selected sample of 1928 healthy women in western New York.
Additionally, as previous studies have found lower rates of depression and obesity in adults with higher educational attainment, the researchers further investigated whether educational status influenced the BMI-depression relationship. They hypothesized that increased weight status beyond what is considered “normal” weight would be associated with increased odds of depression, and that level of education would modify this association.
Participants completed a self-report measure called the Center for Epidemiologic Studies Depression Scale questionnaire (CES-D). Trained interviewers collected various information to related to areas such as lifestyle, demographics, and medical history, and they measured BMI using a standard protocol.
Based on BMI, participants were grouped into the category of “Obese I,” indicating low risk, or a combined category of “Obese II/III,” indicating moderate-to-high risk. Participants’ income was classified into the following categories: less than $20,000; greater than or equal to $20 000 and less than $40 000; greater than or equal to $40 000 and less than $60 000; and greater than or equal to $60 000
According to results, women in the Obese I category had odds of depression that were 43% higher than those of normal-weight women, and the odds were 57% higher among women in the Obese II/III category. Contrary to their hypothesis, the researchers found that women in the Obese I category who had graduated from college had almost double the odds of depression (adjusted OR=2.82, 95% CI 0.99-8.08) as women in the normal-weight category with the same level of education. This association was not observed in participants in the Obese II/III category.
This finding contradicts previous research showing higher odds of depressive symptoms in women with obesity and lower education attainment compared with normal-weight women with equivalent education levels. “This contradictory finding may reflect growing evidence from varied methodological approaches that show individuals with higher educational attainment have an increased risk of comorbid depressive symptoms and obesity, compared to those with less education,” the authors wrote.
However, other findings have linked lower education with higher odds of depression and obesity, possibly because of limited economic and social resources that would facilitate coping with mental health conditions. One study of U.S. adults found evidence suggesting that lower levels of educational attainment may increase the risk of comorbid depression and obesity. Additional studies are needed to clarify these associations and inform treatment implications.
Kranjac AW, Nie J, Trevisan M, Freudenheim JL. Depression and Body Mass Index, Differences by Education: Evidence from a Population-based Study of Adult Women in the U.S. Buffalo-Niagara Region. Obes Res Clin Pract. 2016; doi:10.1016/j.orcp.2016.03.002