Depression and Obesity: Is There a Genetic Link?

It's clear that there's a link between depression and obesity, based on the research that has already been carried out. However, it isn't yet clear whether these two disorders are linked genetically or otherwise.

Reviewed and approved by the doctor Leonardo Biolatto.

Written by Edith Sánchez

Last update: 03 May, 2023

Science has found links between depression and obesity, but it isn’t yet clear whether this is a genetic link or whether it’s due to other factors. At the moment, the available data are contradictory and don’t allow a definitive conclusion to be drawn.

There are several studies that talk about a link between depression and obesity. In fact, one of these studies directly suggests that such a link is genetic. However, new research has challenged these assumptions.

It has even been suggested that it’s obvious that there’s more depression in obese people, simply because of the psychological and social implications of being overweight. In turn, depressed people change their eating habits and this can lead them to becoming overweight.

Let’s see, then, what information there is about it in the scientific community.

Body mass index and depression

A study conducted at the University of Exeter (England) and the Cancer Research Centre of the University of South Australia, in 2018, is considered the most comprehensive so far. In its preliminary conclusions, the research points out that a high Body Mass Index -BMI- implies a high risk of suffering from depression.

The research was published in the International Journal of Epidemiology. It’s based on data collected in a genetic information bank on 50,000 people between the ages of 37 and 73, who had been diagnosed with depression. They compared these data with those of 29,000 people who were neither depressed nor overweight.

In the end, they found that for every 4.7 points increase in BMI , the probability of having depression increased by 18%. In the case of women, this percentage rose to 23%. The study added that men who were too thin were also more likely to suffer from depression.

Depression and obesity: a genetic link?

In 2012, a study developed by researchers from the University of Granada, Spain, led by Dr. Margarita Rivera Sánchez, was made public, suggesting that there is a genetic link between depression and obesity.

The research pointed out that depression modifies the effects of the FTO gene, also known as the “obesity gene”. The consequence of this, according to the study, is that people with depression have an increase in their Body Mass Index (BMI).

To reach these conclusions, also preliminary, a database of 2,440 individuals diagnosed with depression was used as a basis, contrasting their data with a control group of 809 healthy individuals. The analyses led to consider that obesity problems are more frequent in those suffering from depression.

The obesity gene

In 2019 a new study was carried out, this time advanced by Skarmeta’s group from the Andalusian Center for Developmental Biology in Seville; and that of Marcelo Nóbrega, from the Department of Human Genetics at the University of Chicago. The results were published in the journal Nature.

In this research, they pointed out that in recent years nearly 2,000 studies have been published in which the FTO gene has been identified as the “obesity gene”. However, for these researchers, the data is incorrect. Although this gene is involved in fat metabolism , the true obesity gene would be Iroquois 3 or IRX3.

IRX3 has essential functions in virtually all human viscera and its action occurs mainly in the hypothalamus of the brain. The researchers indicated that only 25-45% of obesity cases are due to genetic causes.

Obesity and depression can be linked in a vicious circle. Obese people feel depressed because of the psychological consequences, and depressed people eat worse because of their condition

There is no gene for depression

To complete the picture, in 2019 the American Journal of Psychiatry published a study led by Richard Border, a geneticist at the University of Colorado. This expert, along with his team, analyzed the genetic data of 620,000 people. From this, they came to the conclusion that there’s no gene for depression.

The researchers compiled information on 18 genes that have been referred to as incidents or determinants of depression. At the end of the study, they pointed out that none of these, nor the associated groups, determine depressive states. Each gene has only a minuscule effect on mood disorders.

This research debunks the idea that depression is an exclusively genetic disorder. It also debunks the notion that there’s a “depression gene“. It doesn’t rule out the possibility that hereditary factors are involved, but suggests that they make up a complex network of associated genes, which has yet to be discovered.