Genetic approaches to understand the complex links between obesity, socio-cultural factors and mental health. PhD in Medical Studies (MRC GW4 BioMed DTP)

Supervisory team:
Dr Jess Tyrrell, College of Medicine and Health, Institute of Biomedical and Clinical Science, University of Exeter
Dr Laura Howe, Faculty of Health Sciences, University of Bristol
Dr Amanda Hughes, Faculty of Health Sciences, University of Bristol

Obesity and mental health problems are global issues, but the links between them are complex with sociocultural factors playing a key role. The student will train at 2 world leading centres, utilising global studies (e.g. UK Biobank) and genetic approaches to understand complex relationships between obesity, sociocultural factors and mental health.

Growing evidence suggests bidirectional relationships between higher BMI and higher depression risk. There is also evidence that both high BMI and depression can lead to reductions in socioeconomic position (SEP; e.g. income and employment) and affect social factors (e.g. wellbeing and cohabitation). However, the causality of these relationships and the underlying mechanisms require further study. This project will aim to establish a more complete understanding of the complex relationships between obesity, depression, and socioeconomic factors. The project will include studies from diverse global settings (e.g. Chinese Kadoorie Biobank and Pelotas Birth Cohorts), as well as UK data (e.g. UK Biobank).

The overall aim will be achieved by addressing several questions: 1. Is there a bidirectional causal relationship between depression and obesity (or obesity related factors), and does this relationship vary across different sociocultural settings? 2. Does BMI causally influence an individual’s SEP or social factors, and do these relationships vary across sociocultural settings? 3. Does depression causally influence an individual’s SEP or social factors, and do these relationships vary across sociocultural settings? 4. To what extent is the impact of excess adiposity on depression and socioeconomic position independent of metabolic/health mechanisms?

This identification of causal associations in different sociocultural contexts will provide important information about the complex and potentially setting-specific relationships between obesity, depression, and SEP, thereby informing global decisions on medical management and public health strategies for both conditions over the life course. This builds on work led by the supervisory team members in Exeter and Bristol exploring the role of higher BMI on socioeconomic outcomes and depression in UK Biobank.

The student will have the opportunity to develop skills in several cutting-edge methodologies, including genetic approaches (Mendelian randomisation (MR)), and apply these skills to several datasets: 1. Observational associations between BMI and various different sociocultural and mental health variables in several studies. 2. Utilise one- and two-sample MR to explore the causal effects of BMI and depression on each other, and on SEP. This will include exploring whether the causal effects differ by setting, and investigating potential mechanisms, e.g. by uncoupling the adverse metabolic health effects of obesity using genetic variants that raise BMI but are associated with more favourable metabolic profile. Non-linear models and familial effects will also be explored. The student will work across disciplinary boundaries, with their supervisors coming from molecular/genetic, epidemiological and advanced biostatistical backgrounds and collaborators from psychiatric genetics. They will work with other academic centres outside of the GW4 (e.g. King’s College London).

To apply for this project, please complete the application form at https://cardiff.onlinesurveys.ac.uk/gw4-biomed-mrc-doctoral-training-partnership-student-appl by 5pm Friday 25 November 2019.