And so the incidence of skin cancers, including potentially fatal melanoma, continues to rise. This year, 3.5 million new cases of superficial but often disfiguring skin cancers, and an estimated 68,720 melanomas, will be diagnosed among Americans.

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Many people think a tan protects them by helping block the damaging effects of UV radiation. In fact, a tan represents skin damage. Even brief exposure to ultraviolet light can cause mutations in the DNA of skin cells, including the melanocytes, the host cells for melanoma. Accumulate enough of those mutations and a cancer can result.

“As we age, the number of mutations increase and our immunity wanes,” Dr. Wagner explained  a double whammy that greatly increases the likelihood of skin cancer.

Even those who escape cancer will eventually experience the aging effects of repeated tanning: loose, wrinkled, leathery skin that can make people look decades older than they are. My paternal grandmother, who lived a block from the beach in Brooklyn and swam daily in the years before sunscreens, had what we called “elephant skin” by her 50s. But my 90-year-old Aunt Gert, who lives nearby and winters in Florida but never went to the beach or sat in the sun, has the skin of a 60-year-old. Summarizing the mounting evidence for the addictive potential of UV radiation, Dr. Hornung said in an interview that frequent tanners showed signs of both physiological and psychological dependence. As with cigarette smoking and heavy drinking, which are “often practiced despite knowledge of their dangers,” she said, attempts to curtail UV abuse through education about its dangers seem to fall on deaf ears.

Clearly, something else is driving the behavior, and for some people that something seems to be addiction.

In Dr. Wagner’s study, conducted with Dr. Molly M. Warthan and Tatsuo Uchida, two tests of substance abuse were administered to 145 people basking in the sun on Galveston Island Beach. One is a modified version of the test often used to root out alcohol addiction. It’s called CAGE, an acronym for four questions: Have you ever felt you needed to cut down on your tanning? Have people annoyed you by criticizing your tanning? Have you ever felt guilty about tanning? Have you ever felt you needed to tan first thing in the morning  as an eye opener?

The authors, who published their report in 2005 in The Archives of Dermatology, found that 26 percent of the beachgoers met the CAGE criteria for addiction. And in a second test, a modified version of the psychiatric profession’s official diagnostic criteria for a substance abuse disorder, 53 percent of the respondents scored positively.