Good night's sleep may slow disease.

• Position: Cancer Therapy

A good night's rest may be one weapon in the fight against cancer, say researchers at Stanford (Calif.) University Medical Center. Their work is among the first to piece together the link between mental well-being and cancer recovery. Previous studies have fauna people with cancer who go through group therapy or have a strong social network fare better than those with weaker social support. The question has been how psychosocial factors exert their influence on cancer cells.

"Psychosocial factors affect your behavior patterns, such as exercise, what you eat and drink, and your sleep," points out School of Medicine professor David Spiegel. Of these factors, how well you sleep can seriously after the balance of hormones in your body. This makes the sleep/wake cycle, called the circadian rhythm, a good candidate for linking a person's social network to his or her cancer prognosis. Spiegel mentions two possible ways in which the circadian rhythm may influence cancer progression. The first involves a hormone called melatonin, which the brain churns out during sleep. Melatonin belongs to a class of compounds called antioxidants that mop up damaging free-radical compounds. With a disrupted circadian rhythm, the body produces less of it and the cell's DNA may be more prone to cancer-causing mutations.

Melatonin also slows the ovaries' production of estrogen. For many ovarian and breast tumors, estrogen spurs the cancerous cells to continue dividing. Night-shift workers produce less melatonin and therefore may output more...