Over 1 million Americans visit a tanning booth every day, despite warnings that tanning can cause skin damage and cancer. It's possible these people just can't help it: Some are "tanorexics" who are addicted to the UV radiation that comes from a tanning session, according to a new study in the journal Addiction Biology. Here's what you should know:

What did the researchers find?
They exposed seven habitual tanners to two kinds of tanning beds — one, a regular tanning bed with UV radiation, and the second with filters to block it. During the UV tanning session, the subjects all had increased blood flow in three areas of the brain associated with rewards and reinforcement. When UV light was blocked, those brain regions were not stimulated, and the participants expressed a desire for more tanning time, which didn't happen after the unfiltered UV sessions. 

Is that similar to what happens to drug addicts?
Yes, according to the study's authors. "We saw brain changes that are consistent with that of other things that are considered rewarding such as money, food, or drugs," says Dr. Bryon Adinoff, as quoted in U.S. News. "The same areas of the brain lit up, and we know that if something is rewarding to the brain, there is the potential for addiction."

Is tanning really so bad?
Yes, health experts say. In addition to premature wrinkles and other kinds of skin damage, UV radiation — whether from a tanning booth or a day in the sun — greatly increases the risk of skin cancer. Excessive UV exposure can cause melanoma, the most serious type of skin cancer, which is difficult to treat and often results in death.

Can't people quit tanning when they want to?
In many cases, no. Doctors report patients who have undergone repeated treatments for skin cancer and continue to visit tanning salons. Lori Greenberg, who was recently diagnosed with malignant melanoma, is convinced that she's a tanorexic: "You need it almost on a daily basis," says Greenberg, as quoted by ABC News. "I have skin cancer and yet I still go."

Sources: ABC News, MedPage Today, NY Times, U.S. News