Aetiology of Depression: Insights from epidemiological and genetic research

This thesis includes several population-based studies that explore the aetiology of depression, with a specific interest on biological factors, genetics and epigenetics, and physical health factors for depression. Unravelling the aetiology of depression could potentially answer some remaining questions about depression, and finally may explain why we consistently fail to develop effective management and treatment tools for depression. Therefore, this thesis aims to apply advanced epidemiological studies and to extend the existing knowledge on the aetiology of depression.
Using population- based data, the studies described in this thesis examine several risk factors and predictors that may enlighten the pathophysiological mechanism that underlie the development of depression. Specifically, Chapter 2 of this thesis presents longitudinal studies that examine the impact of potential biomarkers, such as vitamin D (Chapter 2.1), and inflammatory markers (Chapter 2.2) on the occurrence of depression.
Chapter 3 of this thesis presents two studies which apply advanced genetic epidemiological methods to study the genetics of depression.
Chapter 4 focuses on the epigenetics of depression and presents the largest epigenome wide association population-based study so far. Moreover, we dedicated a chapter to the impact of physical health conditions such as myocardial infarct on depression (Chapter 5.1) as well as one to the physical consequences of depression such as cognitive decline (Chapter 5.2).
Finally, Chapter 6 provides a more general discussion of the main findings in this thesis and addresses several methodological considerations of the studies. Clinical implications of the results in this thesis, and future directions are also presented.