In the largest study so far, it was found that the causes behind the high correlation between obesity and depression could be genetics and not necessarily changes in metabolism.
They found that genetically determined for a higher BMI was related to higher risks of depression, with a greater risk for women.
The fact that depression and obesity are usually related is not a secret. In fact, there are already several studies that have confirmed that patients with the second usually suffer from the former.
What has not been established is what first appears: is depression the cause of habits that lead to excessive weight gain? Or does excessive weight gain lead to emotional and metabolic reactions that can lead to depression? Are the genes that make someone more susceptible to obesity related to those that make them more susceptible to depression?
A recent survey, the most complete one done in this respect, seems to solve the question. According to the study conducted by researchers at the University of Exeter (England) and the Cancer Research Center at the University of South Australia, he found preliminary results that High Body Mass Index (BMI) is an indicator of a high risk of depression.
"A higher BMI, with and without its adverse metabolic effects, is likely to play a causal role in determining the likelihood that a person will be depressed," reads the findings from the study published in the International Journal of Epidemiology.
To reach this conclusion, the group of 19 researchers analyzed the available data in UK Biobank, a genetic information bank that collects data from approximately 500,000 people aged between 37 and 73 years.
After making a first set of information, the researchers discovered that the BMI of 340,786 people was available on the platform. This large group was questioned to determine whether they had depression or not. So they found that 48,791 participants suffered from depression. The remainder -291,995 people became the control group.
The researchers analyzed 73 genetic variants related to high BMI and high risk of heart disease, and looked at 14 other variants that are related to a higher percentage of body fat, but that do not increase the risk of heart disease.
This double analysis aimed to distinguish the physiological causes of depression, with its purely psychological appearance. "Although the first group could be linked to depression through biological or psychological mechanisms, only a psychological effect would be expected from the latter group", the researchers explained to The Guardian.
This is how they found that genetically determined to have a higher BMI was related to greater risks of depression, with a greater risk for women.
In fact they found that for every 4.7-fold increase in BMI, the risk of depression increased by 18% in general, and by 23% among women.