In research that suggests that either nature has a sense of humor or believes in the “jolly fat man” stereotype, scientists have found that the same gene that has been associated with obesity may also produce a lower risk of depression.
In the study, published in the journal Molecular Psychiatry, researchers in Canada examined data on over 17,000 people who had participated in studies on genetics, and found that about 3,200 of them suffered from depression. Correlating this with the subjects’ genetic results, they found that the subjects who carried a variant of the FTO gene – which has been proven in past studies to be linked with a tendency towards becoming obese – were 8% less likely to suffer from depression. As the study authors commented, this finding “suggests that the FTO gene may have a broader role than initially thought, with an effect on depression and other common psychiatric disorders.”
The researchers then followed up their initial study by examining three additional international studies conducted on large number of subjects (bringing the total number of subjects studied to over 28,000 worldwide), and found that the “protective” nature of the FTO gene seemed to be reflected in those studies as well. Carrying one copy of the FTO gene decreased the risk of depression by 8%; carrying two copies of the gene decreased that risk by 16%. Study author David Meyre of McMaster University said, “The difference of 8 percent is modest, and it won’t make a big difference in the day-to-day care of patients. But, we have discovered a novel molecular basis for depression.”
Why would this be true?
It’s an interesting question, one that perplexes scientists to some extent. Although it has long been known that genetics and heredity play a role in depression and may be responsible for up to 50% of it, earlier studies had failed to convincingly make a case for having identified either the “depression gene” or the “anti-depression gene.” As Meyre said of his findings, “This is the first gene ever convincingly associated with depression.”
The findings are, after all, counter-intuitive. Obesity is a known risk factor for depression, and vice-versa. With this in mind, Meyre and his colleagues began their study with the assumption that the FTO gene would increase the risk of depression; instead they found that it decreased it. They postulate that FTO may not be as much of an “anti-depression gene” as it is a “happiness gene,” making a contribution to our moods and how we feel about ourselves and the world around us. The FTO gene “methylates” DNA, and thus has the role of turning other genes off and on – thus its ability to influence a number of different phenomena, including both appetite and the happiness that comes from satiety, or feeling “full” and thus happier.
Meyre also theorizes that the FTO gene may have been evolutionarily “selected for” in our ancestors, because in times of low food availability or famine, the ability to store fat was an advantage that permitted the more chubby cavemen to survive while the more fashionably slim cavemen died off. Surviving tends to make one less depressed than the alternative, after all.
So should we give up dieting and decide to be fat and happy?
Not really, for several reasons. First, not everyone carries this particular gene; it is found in only 6.7% of people of African descent, 5.3% of people of European descent, and 2.2% of people of Chinese descent. Second, statistics tell us that most people who are officially obese are not free from depression; just the opposite, in fact. Meyre is the first to point out that all his study indicates is that there is a gene that – if you carry it – may predispose you to be less likely to become depressed.
In other words, it is possible that Santa Claus – the stereotypical jolly fat man – carries the FTO gene, and that helps him to be both fat and happy. Then again, maybe his good mood comes from giving away so many presents. Other studies, after all, have shown that seeing smiles on other people’s faces on a regular basis prevents depression, too.