It doesn't matter whether you are exposed to natural sunlight or artificial sources of ultraviolet radiation, such as tanning beds; overexposure to UV radiation is linked to skin cancer. Tanning bed use may be even more troubling than previously believed as a new study shows indoor tanning is responsible for over 150,000 skin cancer cases a year.

Tanning beds have been directly linked to more than 170,000 cases of basal and squamous cell skin cancer each year nationwide according to the report, which was published in BMJ.

"Not only do tanning beds cause melanoma, the most deadly form of skin cancer, but our study shows they also contribute to the most common cancer, basal and squamous cell skin cancer," lead researcher Dr. Eleni Linos, an assistant professor of dermatology at the University of California, San Francisco told HealthDay.

Researchers analyzed 12 studies that included more than 9,000 cases of non-melanoma skin cancer cases. Among those who reported using tanning beds, they were at a 67 percent increased risk for squamous cell carcinoma and a 29 percent higher risk for basal cell carcinoma. People who use a tanning bed prior to the age 35 that risk for non-melanoma skin cancer increases to 87 percent.

Linos and colleagues believe indoor tanning in America accounts for about 3.7 percent of cases of basal cell carcinoma (more than 98,000 cases) and 8.2 percent of cases of squamous cell carcinoma (about 72,000 cases) each year. Researchers noted, "Non-melanoma skin cancer (NMSC) is the most common human cancer. Indoor tanning is a known risk factor for malignant melanoma, but the data on NMSC are less clear because small individual studies have resulted in varied effect estimates."

Lions hope the research "can support public health campaigns and motivate increased regulation to reduce exposure to this carcinogen, especially during early life." Sharon Miller, MSEE, a Food and Drug Administration (FDA) scientist and international expert on UV radiation and tanning, warns any tan is an indicator of skin damage.