One in five Americans will develop skin cancer, and a person's risk of the disease doubles if he or she has had five or more sunburns, according to a report in the April issue of the Mayo Clinic Health Letter.

Basal and squamous cell carcinomas, the most common and treatable types of skin cancers, had long been considered a problem only for people over 50, according to the report. But Mayo Clinic researchers found that the percentage of women under 40 with the more common type, basal cell, tripled between 1976 and 2003, while the rate of squamous cell cancers increased four-fold.

In the same study, the researchers found that just 60% of the cancers they identified occurred on skin frequently exposed to the sun, such as the head and neck, rather than the normal 90%. Most of the remaining cancers were seen on the torso. The researchers suspect this may be due to more widespread use of tanning beds.

Two types of ultraviolet (UV) light are implicated in skin cancers, the article explains. UVA, which penetrates deeper into the skin and impairs its immune defenses, is more responsible for melanoma, the most deadly type of skin cancer. UVB exposure causes sunburn, as well as squamous and basal cell skin cancers.

Tanning, dermatologists have found, makes the skin give off endorphins. These opioid compounds make a person feel good. They are the reason endurance runners report "runner's high." Could there really be such a thing as tanner's high?

The author of the 2005 report suggesting that frequent tanning may be a type of substance abuse is Richard Wagner Jr., MD, deputy chairman of dermatology and director of dermatologic surgery at the University of Texas Medical Branch at Galveston. Wagner says the idea came from skin cancer patients who couldn't stop tanning.

"Every dermatologist will tell you there are some patients we are concerned about," Wagner tells WebMD. "We know ultraviolet (UV) light can lead to skin cancer. Yet we all see patients with skin cancer who are always tan. We tell them not to tan on purpose, and some say, 'But doc, I like it too much. It makes me feel relaxed. I know I am getting skin cancer, but I can't stop.'"

So Wagner went down to the beach and gave addiction questionnaires to people who were sunning themselves. As many as half met the psychological criteria for substance-related disorder. That substance: sun tanning.

The melanoma on his leg was 6mm in depth.

He knows that, because of the delay in diagnosis, his chances of surviving the next five years are 50/50.

"My Breslow depth (a method for measuring the depth of the tumour, used to predict a patient's chance of survival) for the mole on the back of my leg was off the scale. It came in at a whopping 6mm depth.

"It was because it was bleeding that my family pressured me to get it checked out, I really thought it wouldn't have been as serious as it was.

More than 1300 Australians die each year from skin cancer and those who use solariums are increasing their risk of the illness. Solariums emit ultraviolet rays up to five times stronger than the midday summer sun, information from the Cancer Council shows. Despite this, young people are flocking to tanning clinics particularly in the lead up to summer.

Associate Professor John Kelly from the Victorian Melanoma Service said an increasing number of his patients were frequent solarium users.

"These are people who are paying the ultimate price for fashion," Prof Kelly said. "The irony is that by making themselves look more attractive, they're actually putting their health at risk and causing premature ageing."

He said many Australians falsely believed solarium tanning was safer than sunbaking.

Mayo Clinic researchers studied only basal and squamous cell carcinomas, cancers that are almost always curable and that together afflict 1 million Americans a year, according to the article, published in today's Journal of the American Medical Association. The cancers, caused largely by overexposure to ultraviolet light from the sun, usually develop in older people who have spent many years outdoors.

In the study, doctors focused on people under 40 in Olmsted County, Minn. From 1976-1979 to 2000-2003, the combined rate of the two diseases grew from 19 cases per 100,000 people to 33 per 100,000 — a 74% increase.

Although up to 90% of such cancers typically appear on the head and neck, doctors in the study found 40% of skin cancers on other parts of the body, a change that probably reflects the effect of excessive sunbathing.

Christenson says it's possible that some of the increase in basal and squamous cell carcinomas could be caused by increased screenings. But, she says, her findings suggest that tanning probably plays a more important role.

Basal and squamous cell carcinomas can be disfiguring, even if they rarely spread or turn fatal, Christenson says. And they kill about 1,000 to 2,000 people a year, the American Cancer Society says.

"For a preventable cancer, that's too bad," Christenson says.

Tests in laboratory dishes show that curcumin made melanoma skin cancer cells more likely to self-destruct in a process known as apoptosis.

The same team has found that curcumin helped stop the spread of breast cancer tumor cells to the lungs of mice.

Bharat Aggarwal of the Department of Experimental Therapeutics at the University of Texas M.D. Anderson Cancer Center in Houston and colleagues treated three batches of melanoma cells, known as cell lines, with curcumin at different doses and for varying times.

The curcumin suppressed two proteins that tumor cells use to keep themselves immortal, the researchers write in next month's issue of the journal Cancer.