Graduation Year


Date of Submission


Document Type

Open Access Senior Thesis

Degree Name

Bachelor of Arts



Reader 1

Stacey Doan

Reader 2

Brian Duistermars

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© 2022 Bryn P Kable


College student mental health has seen a serious decline over the last decade (Esaki-Smith, 2022). One factor that has been linked to both physical and mental disorders is obesity. A common way to operationalize weight is through body mass index (BMI) (Ilman et al., 2015). There is evidence that BMI and depression are correlated linearly in that individuals with higher BMIs have higher levels of depression (Badillo et al., 2022; Simon et al., 2008). The exact mechanisms of this relationship are still generally unknown; thus, the goal of this study was to investigate the relationship between BMI and depression in college students, particularly looking at how body image and cortisol reactivity may explain this relationship. I also investigate the moderating role of gender. The participants were 400 college students aged 18-25 (54.7% female). Participants answered survey questions and gave biological samples including salivary cortisol, height, and weight. Regression analyses first tested the main effects of BMI on depression and found no main effect. Next, a mediation model testing the mediating role of cortisol was also insignificant. A second mediation model testing body image as a mediator of the relationship was significant (B = 4.83, 95% CI [1.74, 8.34]) with results suggesting that as BMI increases, body image decreases, and with a decrease in body image, depression increases. I also examined whether gender moderates the relationship between BMI and depression and found that it was significant (F(6, 379) = 2.98, p = .007). However, simple slope analyses with gender did not reach significance, but overall patterns suggest that higher BMI was beneficial for males (B = -8.9, SE = 4.7, p = 0.06) whereas it was detrimental for females (B = 4.6, SE = 4.1, p = 0.26). The results of this study show that in this sample, it was the psychological/societal factors that explained and changed the relationship between BMI and depression rather than biological factors such as cortisol.