For a long time I've heard that tanning beds cause cancer. Here a quote from an article on MSNBC in 2009:
International cancer experts have moved tanning beds and other sources of ultraviolet radiation into the top cancer risk category, deeming them as deadly as arsenic and mustard gas.
For years, scientists have described tanning beds and ultraviolet radiation as "probable carcinogens."
A new analysis of about 20 studies concludes the risk of skin cancer jumps by 75 percent when people start using tanning beds before age 30. Experts also found that all types of ultraviolet radiation caused worrying mutations in mice, proof the radiation is carcinogenic. Previously, only one type of ultraviolet radiation was thought to be lethal.
I've had a couple physicians tell me that in Canada and other northern countries there's a greater risk of harm from vitamin D deficiency. This would suggest that even though tanning beds are harmful, the risks of tanning beds may be weighted against their health benefits.
Here's a quote from an article on CBC in 2007:
A tanning bed with medium-pressure lamps that generate UVB rays is one way to help the body make vitamin D during months when the sunshine is weak
The article also notes that rates of cancer increase significantly when one is deficient in vitamin D.
Do tanning beds cause cancer? This has long been touted and is widely cited in the media, so I expect there's scientific evidence to back it up.
More difficult to answer is whether the risk of cancer arising from the use of tanning beds is greater than the risk of vitamin D deficiency. Is there scientific evidence illuminating this theory?