There are some fascinating similarities between bulimia nervosa and seasonal affective disorder (SAD). Bulimia is primarily an eating disorder, but it is often accompanied during winter by a worsening of mood and an increased craving for food, especially carbohydrates. SAD, in contrast, is essentially a winter-linked depression that often includes an increased desire for food, especially carbohydrates.

Thus, might bright light, which is an effective, safe, and inexpensive treatment for SAD, also help bulimic patients in the winter? Devra L. Braun, M.D., of the New York Hospital-Cornell University Medical Center in White Plains, N.Y., and her coworkers organized a study to find out, and the answer appears to be yes, they report in the November/December 1999 Comprehensive Psychiatry.

They recruited 34 persons with bulimia either through therapists or newspaper ads to take part in their study, which was slated for wintertime. Eighteen of the individuals formed their placebo group, and 16 their treatment group. None of the subjects met DSM-IV criteria for major depression with a seasonal pattern, although four patients in each group met criteria for current major depression. Three weeks before the study, the subjects started food diaries in which they recorded daily how much they ate as well as how often they binged or purged.

The subjects then received verbal and written instructions on how to use light boxes. Each box was designed to deliver either 10,000 lux white light and serve as the bright-light treatment or 50 lux red light and serve as the placebo dim light. Comments from subjects reassured the investigators that none knew which kind of light was treatment and which was placebo. In fact, all thought they were getting a treatment light. Subjects were told to use the lights for a half-hour daily at home between 6 a.m. and 9 a.m. while watching television; the research assistant or investigator maintained daily phone contact with them to make sure they complied. The study lasted three weeks.

The investigators examined the frequency of binge eating and purging in subjects from the start of the study to its conclusion and found that while there were no differences in purging between the treatment and placebo groups, there was a modest but significant reduction in binge eating in the former versus the latter. What’s more, depression ratings decreased for both groups during the study, yet did not decrease significantly more in the light group, suggesting that light was able to influence bingeing behavior independently of its effect on depression. Thus bright light appears capable of reducing winter binge eating in bulimic patients, the investigators conclude.

How might light do this? Probably by acting on serotonin, the researchers suspect, since it has already been shown to affect the transmission of serotonin and since drugs that boost serotonin have been used successfully to treat both SAD and bulimia.

True, light did not reduce binge frequency as dramatically as the usual treatments for bulimia bingeing—cognitive-behavioral therapy (CBT) and selective-serotonin reuptake inhibitors—did, the researchers concede. Yet even if CBT and drugs can reduce bingeing behavior markedly in many patients, they do not do so in others, the researchers point out. So light, they believe, might be a possible alternative treatment for the latter.