The researcher says that overweight can cause depression and its effect is largely psychological.
Although previous studies have found that people with obesity have more depression, it has not been clear whether it depends on depression that causes weight changes or vice versa.
Experts from most of this type of study now say that genetic variants associated with high body mass index (BMI) can lead to depression with a more powerful effect on women than men. In addition, they say that the study suggests that the effect could be the same as the body image.
"People with more overweight people are more overwhelmed, and this is probably at least partly [a] BMI effects [on] "said co-author of the study, Prof. Tim Frailings of Exeter School of Medicine.
Writing in the International Epidemiological Journal, UK and Australian researchers describe how they used data from the UK's Biobank, research efforts involving 500,000 participants aged 37-73, who were recruited from 2006 to 2010. A year
Researchers studied 73 genetic variants associated with high body mass index, which are also associated with higher risk of disease, such as diabetes and heart disease. They also looked at 14 genetic variants related to high levels of body fat but which were associated with a lower risk of such health problems.
The team then searched the participants' hospital data and answers from many surveys – including a self-assessment of a family or psychiatrist's vision for anxiety or depression. The team identified about 49,000 participants who they believed was depressed.
In general, the team found that people with more BMI would be more upsetting.
Researchers also found that the genetic predisposition to greater BMI is associated with depression and women's exposure to women is stronger than that of men. The results occurred even if they performed additional tests, such as excluding individuals with a family history and when the analysis was repeated after a large international project called the Psychiatric Genomics Consortium.
By focusing on 73 genetic variations and taking into account factors including age and gender, they found that an increase in body weight by 4.7 points increased by 18% and in women by 23%, based on 73 genetic variations.
When the team combined data from different sources, they found 14 genetic variants that increase body fat, but are not related to metabolic disorders, and were also associated with a higher probability of depression.
"It shows that the psychological component is as strong as any physiological component if [the latter] or at all, "Frailings said, pointing out that a bad body image might be one of the mechanisms in the game.
The study has some limitations: it mainly addressed individuals with a white European-origin subject and included some self-portraiture data.
Although the study does not show that weight gain for other reasons increases the risk of depression, Frailings said that this is possible. "It allows [one] to conclude that a greater impact on BMI could affect depression, "he said.
Naveed Sattar, a professor of metabolism at the University of Glasgow, welcomed the study. "These new discoveries are probably the most powerful to suggest more weight, can actually contribute to depression," he said. "Of course, many other factors can lead to depression, but even so, weight loss can be useful in improving mental health for some individuals, while joint strength should help to reduce the likelihood of depression."