Most people tend to react similarly to depression. When they feel down, they lose interest in doing things and enjoying them. The tendency is so prevalent that lack of interest—in people, outings, and even food—is recognized as one of the five clinical signs of depression. "When people are feeling depressed, they end up withdrawing, becoming more internal, becoming more lethargic," said Kelly Klump, who teaches psychology at Michigan State University.
But there also exists a subset of people who tend to exhibit a different reaction. For these people, depression breeds high levels of impulsivity. They do things they wouldn't otherwise do.
Like opening a pint of ice cream, and polishing it off.
That psychological quirk — the tendency to become more impulsive when feeling less content — is often referred to as "negative urgency." And negative urgency is actually considered by some experts to be a specific biological trait in people, just like alcoholism has been found to be the extension of specific biological impulses. As a result, people who exhibit negative urgency, turning to binge eating when they're depressed, are not merely demonstrating a lack of willpower or an ordinary mood swing. They're engaging in a biologically driven behavior.
That doesn't mean, of course, that a single episode of binge eating means someone is showing signs of clinical depression. Rather, it suggests that depression and binge eating share a deep, biological relationship that might explain why some of us will finish a box of Oreos after a tough day of work and others will be satisfied by a single cookie.
"For the longest time, people thought that impulsivity is what was linked to binge eating," Klump said. "The thinking was that people who binge ate did so simply because they were impulsive. But it's actually a lot more specific than that. It's not really people who are impulsive so much as people who become impulsive when they are depressed."
New research by Klump, along with Sarah Racine, who teaches psychology at Ohio University, shows how interwoven this tendency towards impulsivity and a proclivity for binge eating really are. Their latest study, published in the International Journal of Eating Disorders, furthers Racine's conviction that "negative urgency" might be the single largest predictor of who is and isn't prone to binge eating.
Klump and Racine, along with five other researchers, tested the association by dividing over 600 women into four groups. In three of the groups, the participants exhibited some form of binge eating—a tendency to eat too much, a tendency to feel as though one's eating is out of one's control, or both. In the fourth, participants had no history of binge eating whatsoever. The researchers used a detailed questionnaire to investigate how women responded to different situations. And they used the results to gauge the relative level of negative urgency of different women--that is, the likelihood of becoming impulsive when down of the women in each group.
What they found is that the only people who tended to do impulsive things when they were depressed had a history of binge eating. Those who didn't act impulsively, meanwhile, did not.
"It was fairly clear," said Racine. "Every component of binge eating that we tested is associated with negative urgency."
Racine didn't establish the concept of negative urgency—the existence of the trait was first discussed in the early 2000s, and it has been a frequent topic of research ever since. A 2008 study divided impulsive people into two categories—those who act rashly when they are excited or happy, and those who do when they are sad or depressed. A 2011 study links negative urgency to problem drinking, which is often viewed as a precursor to alcoholism.
The genetic roots of binge eating are also suggested by more than just the psychological tendencies of certain people. Klump, whose lab at MSU focuses on genetic and biological risk factors associated with different eating disorders, points out that there are a number of biological indicators she has found throughout the course of her research. Some of the clearest evidence, she says, is that risks increase after puberty, when many genes begin to fully express themselves.
But Racine's research has played a key role in furthering our understanding of the emotional trait, and its ties to eating disorders. In 2013, she published research that established that negative urgency has a genetic component.
The connection between negative urgency and binge eating, while it might seem innocuous, is actually a big deal. Since the former is considered a trait with a genetic component to it, it's increasingly likely that the latter—or at least a predisposition to it—is the same.
"Not everyone who has a bad day is going to turn to food to cope with that negative emotion," said Racine. "But those who do are likely wired to."
In other words, the next time you find yourself in a rut, and eating too much, know that the unbecoming scene isn't merely a question of will power—it's rather, in all likelihood, a matter of your genetic makeup.