As a breast cancer researcher, Dr. Horng-Shiuann Wu has examined closely how the disease drains energy of patients, who often suffer in private. Fatigue, depression and insomnia are common after chemotherapy or radiation treatments end, Wu says. One path to comfort Wu tests is light therapy, commonly used to treat winter depression for people who are sensitive to lack of sunshine. Wu says cancer disrupts the body’s circadian rhythms, which are affected by exposure to light. Adding artificial blue-green light to cancer patients’ daily routines can alleviate fatigue, lack of sleep and depressive mood it's an inexpensive, simple non-drug treatment.