Light Therapy Lessens Bulimics' Binging and Purging

April 6, 2001 -- That light box some people use to beat the "winter blues" may do more good for our minds than we thought: They may be useful in treating other mental disorders, including eating disorders.

Phototherapy -- or the regular use of concentrated bright light -- is a widely recognized treatment for the cyclical bouts of depression experienced by many who have seasonal affective disorder, or SAD. New evidence now shows that light therapy may benefit women who have both SAD and anorexia bulimia, an eating disorder characterized by binging and purging.

The therapeutic effect of light on patients with bulimia underscores the connection between depression and eating disorders, which frequently become worse during winter months, explain Raymond Lam, MD, and colleagues in a report in March's Journal of Clinical Psychiatry.

Lam and colleagues believe the light may relieve binging and purging indirectly by improving mood.

"Light therapy may directly improve mood in these bulimic patients with SAD and thus indirectly improve dysfunctional eating behaviors," write the researchers from the University of British Columbia in Canada.

Twenty-two patients with both SAD and bulimia received a four-week trial of light therapy, with each session lasting 30 minutes to one hour.

Not surprisingly, measures of mood improved considerably following treatment. More important, the number of binges decreased by an average of 46%, and the number of purging events dropped by 36%, they report.

While 10 of the 22 patients had a complete remission of depressive symptoms following the trial, only two of the patients completely stopped their binging and purging behavior.

What that suggests, they say, is that eating disorder behaviors may persist as a habit, despite underlying changes in brain chemistry.

"Theoretically, ... a longer period of light treatment may be required to produce higher abstinence rates in binge and purge episodes," they write.

Despite the preliminary nature of the findings, Norman Rosenthal, MD, an early pioneer in light therapy for SAD, says the beneficial effects of phototherapy in eating disorders should come as no surprise.

"Light is not just an arcane treatment for a specific illness, namely seasonal affective disorder," Rosenthal tells WebMD. "Light is probably doing many things in the brain, and because light is such a fundamental principal in the biology of humans, we can expect that it will have many physical effects on the body. These effects may be used in different ways for therapeutic purposes."

Rosenthal is clinical professor of psychiatry at Georgetown University School of Medicine in Washington, D.C., and author of the book Winter Blues.

He suggests that in bulimic patients, the purging that follows binge eating is not merely a frantic effort to lose the weight one has gained, but may be indulged in because it makes the bulimic feel good. And he believes that light affects the brain in such a way as to both diminish the need for food and to dampen the need for the good feelings that come with purging.

Rosenthal also says that light increases brain levels of serotonin, a chemical involved in mood that also regulates the sense of "satiety" -- the feeling of being full after eating. Thus, it may counteract the feeling that bulimic patients report of never being "full enough," he says.

"If light therapy boosts serotonin, that could easily explain how the brain is letting the person know that the patient is full," Rosenthal says.

As if to bring things full circle, some evidence -- not fully explored by researchers -- suggests that people eat more in the winter months and that patients with eating disorders experience a worsening of symptoms.

"That ties together the effect of light on both seasonal affective disorder and eating disorders," Rosenthal says.