Last reviewed and revised on June 17, 2011
By Michael Craig Miller, M.D.
As the day winds down in my house, the TV is tuned to late news, a review of the day's sports action or a talk show. This is when I often find a late-night snack irresistible. It's never clear to me where the impulse comes from. Maybe it starts with a bit of hunger, but I'm just as likely to make my way to the kitchen without thinking. And the temptation to eat is great enough that I have to be more mindful of the habit. I know that I'm not alone.
The occasional late-night snack is nothing to worry about. But nightly bingeing merits a closer look. Experts may debate whether nocturnal overeating needs its own diagnostic category, but they don't debate the significance of the problem.
Sleep-related eating syndrome is a highly-publicized malady, though it's not clear how common it is. People with this problem eat while sleepwalking, or while in a twilight state between sleep and wakefulness. They generally aren't conscious of what they're doing, so they may wake up to find the bed littered with candy wrappers with no memory of consuming the candy.
A better-documented problem is night eating syndrome, in which people do the majority of their eating late at night. A 1999 study in the Journal of the American Medical Association found that by 6 p.m., people with night eating syndrome consumed a little more than a third of their daily calories, while a control group had consumed almost three-quarters. Between 8 p.m. and 6 a.m., however, the night eaters consumed 56% of daily calories, while controls consumed only 15%.
Night eating syndrome may affect 1 or 2 out of 100 people in the general population. Dr. Albert J. Stunkard, a psychiatrist at the University of Pennsylvania, first described the disorder in the 1950s. Researchers have recently explored its link to weight gain. The problem affects anywhere from 9% to 14% of people seeking treatment at obesity clinics, and as many as 27% of severely obese people.
Night eating syndrome also occurs in people who are treated in mental health clinics. In one study of psychiatric outpatients in Pennsylvania and Minnesota, 12% had night eating syndrome. Night eaters in this study were also much more likely than other individuals to have an addiction problem. Other research indicates that people with night eating syndrome tend to suffer from a distinct form of depression. In contrast to the usual pattern where depression is more pronounced in the early part of the day, night eaters tend to become more depressed during the evening.
It's not clear what causes night eating syndrome and why it is associated with depression or addiction. One theory is that night eating syndrome involves a disruption in the hormones that regulate sleep, appetite or mood. Because late-night snacking usually involves carbohydrate-rich "comfort" foods, this theory holds that night eating syndrome is a form of self-medication.
Scientists note that sleeping and eating are probably connected, given the link between lack of sleep and weight gain. Getting plenty of sleep may be a helpful substitute for nighttime trips to the refrigerator. Until more is known about night eating syndrome, it's probably best to take a broad approach to treatment.
Michael Craig Miller, M.D. is Editor in Chief of the Harvard Mental Health Letter. He is also associate physician at Beth Israel Deaconess Medical Center and assistant professor at Harvard Medical School. He has been practicing psychiatry for more than 25 years and teaches in the Harvard Longwood Psychiatry Residency Program.