"Genetic variants associated with high BMI can cause mental health problems," reports The Guardian.
Depression is more common in people with obesity. However, in previous studies, it has not been possible to determine whether there is a direct causal relationship. Therefore, this could be the case when depression causes weight gain, and not vice versa, or both can be true.
Similarly, obesity-related complications such as type 2 diabetes contribute to depression rather than obesity.
This latest study attempts to use the genetic method to focus on the direct impact of obesity on the prevention of depression, other lifestyle and health factors. Researchers have studied the DNA of about half a million adults with white European origin in the UK.
The researchers looked at 73 genetic variations that previously had a higher BMI. Some of them were also associated with metabolic complications, such as high cholesterol or blood sugar levels, a decrease in risk rather than an expected increase.
Researchers found that combining genetic variants associated with greater BMI was also associated with depression. This was some evidence that even if the person had options that reduced the risk of metabolic complications. This may suggest that obesity affects the risk of depression, psychologically, rather than metabolic changes; at least in some cases.
Although we can not change our DNA by regularly exercising and eating healthy, people can help achieve or maintain a healthy weight, and help people with depression. Read more about how exercises can improve your mood and improve your health.
From where does this story come from?
The study was conducted by researchers from Exeter School of Medicine, University of South Carolina Cancer Research Institute and King's College London.
Researchers were funded by the Diabetes Research and Wellness Foundation, the Australian Research Study Program, the UK Medical Research Council, the Wellcome Trust, the European Research Council, the Royal Society, the Gillings Family Foundation, Diabetes UK, the National Institute for Health Research (NIHR) Biomedical Research Center, the Maudsley NHS Foundation trust and King's College London. The study was published in the revised International Epidemiological Journal on the basis of open access, so it can be freely read online.
The Guardian reported on the study accurately, including limitations. Mail Online provided comprehensive information on a study that was referring to any genetic analysis and concluded that the psychological effect of overweight increases the risk of depression if it was only recommended and not proven.
What kind of research was this?
This was a case control study comparing the genetic composition of people with and without depression.
Depression is more common in people with obesity. However, it is not known whether obesity can directly increase the risk of a person's depression, whether the reverse is true or both.
So the researchers conducted a specific type of case control study, known as the Mendeley Randomization Survey, in which researchers focused on genes known to be associated with disease risk and health effects rather than lifestyle factors.
The idea of this type of research is the precise combination of DNA that people inherit from their parents is a coincidence. Therefore, the analysis reduces the likelihood that other factors (restless) create the link between obesity and depression.
What was the study?
Researchers used genetic information from around 450,000 UK adults with a White European predecessor who volunteered to participate in the UK Biobank and their DNA was explored for research purposes.
Researchers discovered 48,791 people with depression and 291,995 non-depressed people (controls) who measured BMI and compared their DNA.
People were found to have been depressed on the grounds that they reported:
- that they had seen GPs or psychiatrists nerves, anxiety or depression and experienced at least 2 weeks when they felt depressed or inconspicuous
- Records from the UK State Hospital indicate that they have been diagnosed with recurrent severe depressive illness (MDD) or a single episode of MDD
The researchers also looked at whether analyzing only those patients with a hospital diagnosis or who reported that a professional diagnosis of depression had an impact on their outcome.
Researchers have specifically examined whether people with depression are also more likely to have genetic changes associated with obesity.
As a "marker" for obesity, if these genetic variations were more common in people with depression, this suggests that obesity could contribute to the risk of developing depression in people.
Researchers looked at 73 genetic variations that were associated with higher BMI. Researchers switched off variants that were associated with a higher body mass index but had stronger links with other conditions or features such as smoking or lipid levels. Of the 73 variants, 43 were in or near the genes that could affect the functioning and development of the brain and the nervous system (which may theoretically have a direct effect on the risk of depression), but 30 did not. Also, 14 variants were associated with an increased BMI, but reduced the risk of metabolic disease (so they did not affect depression using these metabolic factors).
If it was found that the options associated with greater BMI, but not any of the metabolic consequences of obesity, are more common in people with depression, this could suggest that the link between obesity and depression is associated with psychological effects.
Researchers also looked at men and women separately, because the psychological impact of overweight on women could be higher because of questions about the body's image. They also reiterated their analysis of a second sample of 45,591 people with depression and 97,647 controls from another study group (Conservative Psychiatric Genetics).
What were the main results?
Researchers found that individuals with obesity had a 45% higher probability of depression than body mass index (coefficient 1.45, 95% confidence interval (CI) 1.41 to 1.49). This link was stronger in women than men.
A combination of genetic variants associated with a higher BMI (about 5 kg / m 2) was associated with an 18% higher probability of depression (OR 1.18, 95% CI from 1.09 to 1.28). Women's links were slightly stronger than men, but the difference was not large enough to rule out that it happened by accident.
Researchers found similar results in further analysis to make sure their results are robust, for example by excluding people who have not registered a diagnosis of depression in a hospital.
Links to depression were stronger when looking at BMI-related variants that were also related to the brain or nerves-related genes. But again the difference was not big enough to rule out that it happened by accident.
The link with depression was found in BMI-related variants related to a favorable metabolic profile, but only once aggregated data from samples from Biobank and the Psychiatric Genetics consortium.
How did the researchers interpret the results?
Researchers concluded that a higher body mass index could directly boost an individual's chances of developing depression.
Some medicines used to treat depression can lead to weight gain. People who are depressed may have less care for themselves, including healthy eating and regular exercise, and this may also affect their weight.
This study provides evidence that the relationship between obesity and depression may at least partly be related to the fact that weight has a direct impact on the risk of human depression.
This study was very large and used many complex analyzes to find out the relationship between weight, genetics and depression. The researchers used a study plan aimed at preventing the effects of other factors affecting the outcome. They also carried out a number of additional analyzes to check their results and to make sure they are reliable.
For example, the way people were classified as depressed or lacking in depression may not be completely accurate, as it was partly based on people reporting that they were experienced by "nerve, anxiety or depression" of medical staff. Some people may have had depression but they have not sought help or they have not been diagnosed with depression if they were fully appreciated. However, when researchers excluded people who had no diagnosis of depression in the hospital, they had similar results.
Although this study contributes to what is known about the links between obesity and depression, much remains to be learned. For example, the findings suggest that the link may be psychological, but researchers will now have to consider how obesity can contribute to the risk of depression.
It is also worth bearing in mind that the causes of depression can be complicated and many factors can play a role. Similarly, the results may not be applicable to people of different nationalities.
If you are overweight or obese and you are also anxious about moods or depression, then it may be a good idea to seek help on both issues at the same time.
What we know is that mental and physical health are interconnected, and regular physical activity and healthy eating tend to be beneficial for both.