Women who visit tanning salons more than once a month are 55 percent more likely to develop malignant melanoma, and the risk more than doubles for women in their 20s who frequent tanning parlors, according to an eight-year study of more than 100,000 Scandinavians.

The study, appearing ek in the Journal of the National Cancer Institute, analyzed the lifestyle and melanoma risk for women between the ages of 30 and 50. It was found that sunburns and tanning-lamp use during the adolescent and early adult years significantly increases the susceptibility to the skin cancer.

Melanoma risk is highest among fair-skinned people in Australia, New Zealand, Europe and North America. The level of the skin cancer has tripled in Norway and Sweden since the 1950s, the researchers found. Nearly about 45,000 cases of melanoma are diagnosed annually in the United States and about 7,300 people die of the disease each year.

In the study, an international group of researchers analyzed data from the Women's Lifestyle and Health Cohort Study in Norway and Sweden. The study signed up 106,379 women in 1991 and 1992.

They all completed comprehensive questionnaires about their personal exposures to sunlight and to artificial tanning. In 1999, the researchers rechecked the women's health using the national health registries in Norway and Sweden.

The researchers disclosed 187 cases of melanoma diagnosed among the study group during the eight-year follow-up period.

They discovered that women of any age or skin tone who regularly visited tanning salons once or more per month had a 55 percent increased chance of developing melanoma, but the risk was highest for women in their 20s.

They compared to women who never used a solarium, women between the ages of 20 and 29 who reported using artificial tanning systems once or more per month increased the risk of melanoma about 150 percent.

The results provide stronger evidence than those of other studies that solarium use is associated with an increased risk of melanoma.

Also the study found that the risk of melanoma from sun exposure was about two times higher for blondes than for women with brown or black hair. And for red-haired women, the risk was about four times greater, the researchers said.