Researchers have found evidence that could explain why people continue to sunbathe

Drop by any beach or swimming pool on a summer day, and you'll probably see people doing something they know is bad for them: getting a tan.

Studies show that many of those who regularly tan know that exposure to the ultraviolet rays of the sun or a tanning booth increases their risk of developing skin cancer. But - much to the dismay of dermatologists, who have spent years trying to educate the public on the skin-cancer dangers of ultraviolet radiation - this knowledge doesn't seem to have much effect on their behavior, and the incidence of skin cancer continues to rise.

Now, researchers at the University of Texas Medical Branch at Galveston have found evidence that could explain why people continue to sunbathe and patronize tanning salons despite being aware that the practice is dangerous. Using criteria adapted from those used to screen for alcoholism and drug dependency, they've determined that repetitive tanning behavior may be the product of a kind of addiction.

"Dermatologists often talk about people who seem 'addicted to the sun' - people who know it's not good for them to be bronzed all the time, but don't seem to be able to stop tanning," said UTMB professor Richard Wagner, senior author of the study, which was co-authored by Molly M. Warthan and Tatsuo Uchida and will be published online in the Archives of Dermatology Aug. 15. "It's interesting that by slightly modifying tools used to identify substance-related disorders, we can actually see an objective similarity between regular tanning and those disorders."

Wagner and Warthan asked 145 Galveston beachgoers a series of questions such as, "Do you try to cut down on the time you spend in the sun, but find yourself still suntanning?" and, "Do you think you need to spend more and more time in the sun to maintain your perfect tan?" The interviews were divided into two parts, with four initial yes-or-no queries derived from those used in a standard four-question survey used to identify alcohol abuse or dependence. Seven others were based on the seven diagnostic criteria for substance-related disorders in the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV).

Under criteria adapted from the alcoholism-screening questionnaire (known as the CAGE, an acronym for Cut down, Annoyed, Guilty, Eye-opener), 26 percent of those interviewed were classified as "ultraviolet light (UVL) tanning dependent." The DSM-IV criteria indicated an even greater proportion of beachgoers with UVL tanning dependence - 53 percent.

"This is a new idea, and we didn't know how it would turn out, although there has been mixed evidence from other studies suggesting that tanning increases endorphin production, which could be addictive," Wagner said. "Certainly this could explain why educational interventions haven't been more successful."