Aug. 15, 2011 -- Even though she has been diagnosed with skin cancer five times in the past 11 years, Lori Greenberg says she still dreams about tanning.
"You need it almost on a daily basis," the Wayland, Mass., woman said today. "If you don't ... you feel like you go through withdrawals. It's almost like Xanax or Valium."
Researchers have believed for several years that tanners exhibit similar behavior to alcoholics and drug addicts.
"Certain regions of the brain we know are responsible, partially responsible for drug and alcohol addiction seem to have increased blood flow when you put UV [ultraviolet] light in front of these individuals who are known for frequent tanning," Dr. Charles Samenow, a psychiatrist and professor at George Washington University, said Saturday.
Nearly 30 million Americans tan indoors every year and more than 1 million visit tanning salons every day.
Now scientists say they've seen that addiction firsthand, by peering into the brain.
According to findings due to be released in the journal Addiction Biology, scientists at University of Texas' Southwestern Medical Center examined a group of tanners undergoing a regular, indoor tanning session.
Sunbathers' Feelings Similar to Other Addictions
When the ultraviolet light, which tans the skin, hit the tanners' bodies, the parts of their brains associated with reward and addiction lit up, indicating increased blood flow.
When researchers blocked the UV light, without telling the tanners, the same parts of the brain dimmed and became less active.
"We've found 50 percent of frequent tanners, sunbathers report feelings similar to other addiction," said study author Dr. Bryon Adinoff, an addiction psychiatrist at the University of Texas' Southwestern Medical Center. "They're unable to cut down their tanning. Life focused around getting tan. They get skin cancer and they still tan. These are the kinds of things that we see in people with other kind of addictions."
The researchers' conclusion: UV light revs up addictive urges. They say that the addiction is likely not limited to tanning indoors but also outdoors.
Greenberg, 40, said she was cancer-free, even though doctors last month had found a recurring site for malignant melanoma. She said she still couldn't resist the urge to tan. "I'd say no [to laying out] but I would be lying," she said.
"I smoked before," she said. "I stopped, and I don't have lung cancer. ... Sun-tanning? I have skin cancer and yet I still go."
ABC News' T.J. Winick contributed to this story.