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Genetic and Lifestyle Origins of Inflammation in Depression

Periodic Reporting for period 1 - GLOID (Genetic and Lifestyle Origins of Inflammation in Depression)

Reporting period: 2015-05-01 to 2016-10-31

Depression is a relatively common mental illness that poses substantial societal costs. 15% of people in high income countries and 11% of people in low to middle income countries experience depression during their lifetime and many experience multiple episodes. Depression impairs a person’s ability to function in their role, causing reduced social and economic productivity. By 2030, depression will be the second largest cause of disease burden globally after HIV/AIDS. Thus, depression represents an urgent public health issue. Since the cause of depression is not well understood and current serotonin-based antidepressants are suboptimal, research to identify the biological and behavioural factors that contribute to the onset and remission of depression is critical. The aim of this Marie Skłodowska-Curie European Fellowship project was to examine evidence for the possible inflammatory, metabolic and lifestyle origins of depression. At the conclusion of the project we identified that people’s overall metabolic health and their lifestyle may have substantial consequences for their ongoing mental health.
The first published study examined the link between mental and metabolic health. It focused on metabolic syndrome: five metabolic-related health conditions of abdominal obesity, high blood pressure, high fasting glucose levels, low HDL-cholesterol and high triglycerides. We saw that worse symptoms of depression or anxiety and using antidepressants were related to poorer metabolic health (especially obesity) and short-term worsening of metabolic health. This research highlights that it is important to monitor metabolic health in people with depression and anxiety. It was recently published as an article in the journal Depression and Anxiety.

The second published study focused more closely on unhealthy lifestyle behaviours, specifically the extent to which people with depression and anxiety engage in physical activity. This study found that people with anxiety or depression have lower sports participation and lower general physical activity compared to those without. Furthermore, having depression or anxiety was associated with lower sports participation and physical activity levels two years later. Lower sports participation, lower general physical activity and greater sedentary behaviour were all associated with chronicity of depression and anxiety over time. Thus, over time, there seems to a mutually reinforcing, bidirectional relationship between psychopathology and lower physical activity, particularly low sports participation. This article was recently accepted in the journal Psychological Medicine.

There are other ongoing studies from this project. One study, which was recently presented at the International Society for Affective Disorders conference, examined the consequences of a combination of several unhealthy lifestyle behaviours on depression and anxiety over time. It showed that a combination of factors such as high alcohol use, smoking, low levels of sleep, physical inactivity and drug use was associated with poorer course of depression and anxiety over time. Another study focused on the possible genetic origins of inflammation in depression, although analyses to date have not yielded conclusive findings.

Conducting this work was aided by the completion of formal courses in statistical analysis, epidemiology and genetics. Results have been disseminated in journal articles, conference presentations and via the study webpage: sarahhiles.wordpress.com/about/publications
This research project helped to contribute to a robust evidence base regarding the possible determinants of depression. It particularly highlighted that a person’s lifestyle, especially their integration in organised sports, may have ongoing consequences for their mental health. This work focusing on the possible behavioural origins of depression is particularly useful in highlighting possible opportunities for the prevention and treatment of depression. An important question is how biological theories of depression integrate into the broader framework of the symptoms and behaviour of people with depression. The results of GLOID highlight that people with depression exhibit unhealthy lifestyle. However, lifestyle is seldom a focal point of biological theories. Unhealthy lifestyle may contribute to the observed impairments in inflammatory and metabolic parameters in depression. They are also good targets for intervention that may potently stimulate biological change in some people.