A fairly rare eating disorder whose signature is excessive eating - though not necessarily binging - at night needs further study since it may signal other mental health issues, researchers say.
They analyzed eating disorders and mental health history in more than 1,600 university students and found about 4 percent met night eating disorder criteria, with about a third of those also engaging in binge eating.
"Night eating syndrome is characterized not only by eating at night - certainly many college students might have a late night study fest with eating - but it's also characterized by other things, like feeling that you can't eat in the morning, and feeling like you have to eat in order to go back to sleep," Dr. Rebecka Peebles told Reuters Health.
Peebles, the study's senior author, is an attending physician at the Children's Hospital of Philadelphia, and a researcher in the department of Pediatrics at the Perelman School of Medicine at the University of Pennsylvania.
"Our study helped extend findings of previous studies that have not been controlling for binge eating," Peebles said. "We know that binge eating and night eating have a pretty moderate overlap so a lot of people who come into the clinic for night eating often have binge eating."
"We think night eating is something to be aware of even though it only occurs in just under 3 percent of the students after controlling for binge eating, so it's still a pretty important entity," Peebles said.
Distinguishing night eating from binge eating is important, Peebles and her colleagues write in the Journal of Adolescent Health, for several reasons. Night eating may require a different treatment approach than other eating disorders, which could also be present.
Night eating was also more common in students with a history of anorexia nervosa and in students taking ADHD medications, they report, so those other disorders may play a role in the nighttime eating syndrome.
Night eating disorder is a distinct diagnosis in the newest psychiatric Diagnostic and Statistical Manual (DSM-5), the researchers note.
The syndrome is often characterized by increased appetite at night, but usually takes the form of "grazing" on food all evening, rather than intensive binging, and also may include waking up in the night to eat.
Often the urge to eat is tied to the feeling it that it will improve sleep or allow the person to get back to sleep.
The authors said that young adults tend to eat more at night and college students who are stressed and have inconsistent sleep patterns may be at risk for night eating.
But most previous research on the subject has been limited to small groups and has failed to adjust for the overlap of binge eating disorder among night eaters.
To get a sense of how common night eating disorder is and what other traits or risk factors go along with it, the researchers analyzed data from a large 2008 survey of students in 10 U.S. universities.
A total of 1,636 students were included in the new analysis. About 60 percent were young women and 74 percent were white. About 60 percent of the students were also competitive athletes.
The online survey included information on height and weight, plus four questionnaires focused on night eating, eating disorders in general and health-related quality of life. Scores on the Night Eating Questionnaire (NEQ) were used to diagnose night eating disorder.
Binge eating was also measured by students' reports of details such as a feeling of loss of control over eating. Recurrent binge eating was defined as binge eating large amounts of food at least four times during the previous month.
A total of 67 respondents (4.2 percent) met the criteria for night eating syndrome. They were also more likely than other students to have other eating-disorder behaviors such as excessive laxative use, compulsive exercise and purging, as well as lower quality of life. Another 222 students (14 percent) appeared to be binge eaters.
Of the 67 students with night eating syndrome, 22 were also binge eaters. Excluding the binge eaters from the group of students with night eating syndrome reduced the prevalence of night eating to 2.9 percent.
A history of depression and self-injuring was more common among those with night eating disorder.
"I think it's important to know that it affects both men and women and also all races and ethnicities," Cristin Runfola told Reuters Health.
Runfola, a researcher with the University of North Carolina Center for Excellence for Eating Disorders, led the study.
The study showed that night eating syndrome was also associated with other eating disorder behaviors that could lead to serious physical and psychological consequences, she said.
It's important that people with night eating syndrome get help, Runfola said, adding that parents and friends can spot signs of night eating in young adults.
"You might see fluctuations in weight or you might notice food missing in the house," she said.
"Often times these people are eating throughout the night," she added. "They might even be waking up and feeding multiple times throughout the night, so if you're frequently hearing that someone's getting out of bed throughout the night and you're noticing that food is missing there might be something going on."