Researchers find that people with a higher body mass index more likely to develop depression.
People who are obese may be more likely to develop depression than people who are not overweight, according to a new DRWF-funded report.
While previous studies had looked at genetic variation linked with body mass index (BMI) to provide evidence that a higher (BMI) score could be a cause of depression, tests had not looked at whether this relationship was driven by the metabolic consequences of BMI nor for differences between men and women.
The DRWF-funded study was carried out by researchers from The University of Exeter Medical School, the University of South Australia Cancer Research Institute and King's College London and the results were recently published in the International Journal of Epidemiology.
Researchers removed the effect of other lifestyle and health factors in order to perform a genetic technique to focus on the direct effect of obesity on depression. The researchers looked at the DNA of around 500,000 adults with white European ancestry in the UK.
The researchers looked at 73 genetic variations which had previously been linked to higher BMI. Some of these had also been linked to a reduction in risk of metabolic complications such as high cholesterol or blood sugar levels, rather than the increase that might be expected.
Researchers also looked at whether the psychological impact of obesity could be greater in women because of issues around body image and looked at men and women separately as part of the study.
Researchers concluded: “Higher BMI, with and without its adverse metabolic consequences, is likely to have a causal role in determining the likelihood of an individual developing depression.”
An NHS Behind the Headlines analysis of the study said: “This study provides evidence that the link seen between obesity and depression may, at least in part, be due to a direct impact of weight on a person's risk of depression.
“This study was very large, and used many complex analyses to look at the relationship between weight, genetics, and depression. The researchers used a study design which aimed to remove the chance of factors other than weight impacting the results. They also carried out several additional analyses to test their results and make sure they were reliable.
“For example, the way that people were classified as having or not having depression may not have been entirely accurate, as it was based partly on people's reports of having seen a medical professional for “nerves, anxiety or depression”. Some people might have had depression but not sought help, or might not have had a diagnosis of depression had they been fully assessed. However, when the researchers excluded people who did not have a hospital recorded diagnosis of depression, they got similar results.
“While this study contributes to what is known about the links between obesity and depression, there is still much to be learned. For example, the findings suggest the link may be psychological but researchers will now have to look more closely at how obesity might contribute to depression risk.
“It is also worth bearing in mind that the causes of depression are likely to be complex, with many factors potentially playing a role. Also, the results may not apply to people of different ethnicities.
“If you are overweight or obese and you are also troubled by low mood or depression then it may be a good idea to seek help for both issues at the same time.
“What we do know is that mental and physical health are interrelated, and regular physical activity and eating healthily are likely to be beneficial for both.”
DRWF Research Manager Dr Eleanor Kennedy said: “This research demonstrates the power of DRWF funding in a number of ways. Firstly, it is great to see DRWF research funding making a difference to our understanding of the diabetes landscape. The genetics world is a complex area and to be helping to fund this kind of research is great.
“In addition, though, what we are now witnessing is DRWF’s funding helping in international efforts. Here, a collaboration between the UK and Australia has allowed DRWF’s name to be associated with efforts right the way across the globe that will further our understanding of the condition.”