A Quantitative Exploration of the Mechanisms Relating Obesity, Depression and Socioeconomic Position

Current research on the relationship between obesity and depression suggests that it is complicated and potentially complex. In particular, there are multiple mechanisms that might relate obesity and depression, which may interact with each other as well as being influenced by factors such as age, sex and socioeconomic position. However, there is currently a lack of longitudinal evidence exploring these proposed mechanisms with evidence in support of them relying on cross-sectional associations. Additionally, whilst the associations between socioeconomic position and both obesity and depression are well established, the way in which socioeconomic position influences, or is influenced by mechanisms that might relate the two conditions is unclear.

In this thesis, I will explore evidence for proposed mechanisms relating obesity, depression and socioeconomic position. This exploration is presented in two main stages. In the first stage, I review the literature on the relationship between obesity and depression to examine broadly what is currently known about mechanisms that relate the two conditions. In the second stage, I will analyse longitudinal data from the United Kingdom using a combination of statistical and mathematical modelling. The first of two models presented uses a Structural Equation Model to examine whether functional impairment, physical activity and diet mediate the relationship between obesity and depression bi-directionally, adjusting for the influence of age, sex and socioeconomic position. The second model then uses Agent-based simulation to examine the role of stigma as a mechanism that might produce relationships between obesity, depression and socioeconomic position.