Via BoingBoing, a fascinating hypothesis: could breast cancer be caused by artificial light?

The University of Connecticut cancer epidemiologist says there still is no scientific consensus about why the incidence of the disease is so much higher in the developed world.

The literature on breast cancer is littered with discredited theories about environmental and lifestyle factors that may contribute to the onset of the disease.

"We knew more about the cause of breast cancer 20 years ago than we do today," Stevens said. "What we do know is that it must have something to do with industrialized society."

Only a few theories have withstood scientific scrutiny, and no single factor explains a great percentage of breast cancer cases.

But that hasn't stopped people from looking for new explanations.

Now, Stevens and a few other researchers are focusing on a little-known suspect - electric light.

Their theory that artificial light can cause breast cancer is simple. Prolonged periods of exposure to artificial light disrupt the body's circadian rhythms - the inner biological clocks honed over thousands of years of evolution to regulate behaviors such as sleep and wakefulness. The disruption affects levels of hormones such as melatonin and the workings of cellular machinery, which can trigger the onset of cancer, Stevens theorizes.