Cancer often upends sleep. Medications can offer temporary relief, but in many cases, they’re not very effective, and some people don’t want to add yet another drug to their regimen.

Bright light in the morning may help. Exposure to light stimulates cells in our eyes that influence the brain’s “master clock,” helping to set—and reset—sleep/wake cycles, explains Lisa M. Wu, PhD, a clinical psychologist at Northwestern University’s Robert H. Lurie Comprehensive Cancer Center in Chicago.

In a small study published in the Journal of Clinical Sleep Medicine, men and women who had finished treatment for a range of cancers spent 30 minutes each morning for 30 days using a bright light box. These devices, available commercially, simulate the intensity and color of natural sunlight. Compared with individuals in a control group who looked at dim light, those in the bright light group had a modest improvement in sleep efficiency, meaning the time in bed that is spent asleep rather than awake. “Bright light therapy is a low-risk, low-cost approach,” says Wu.

Even three weeks after treatment ended, study participants were sleeping just as well. One hypothesis is that sleeping better gave them more energy so they were able to get outside more, get exercise (which also helps with sleep) and get exposure to sunlight. “Natural sunlight is brighter than light from any light box,” Wu says. Too tired to get outside? It also helps to sit next to a window with natural light exposure. Be sure to let the light reach your eyes.