Excerpt from The Melanoma Research Foundation:
"As many as 90% of melanomas are estimated to be caused by ultraviolet (UV) exposure. This includes UV exposure from the sun and from artificial sources, such as tanning beds. The World Health Organization’s International Agency for Research on Cancer (IARC) classifies tanning beds and tanning lamps into its highest cancer risk category – carcinogenic to humans, the same category as other hazardous substances such as plutonium and certain types of radium."
"Numerous individual studies, including an analysis of several studies combined (meta-analyses), have consistently shown that indoor tanning increases the risk of developing all forms of skin cancer, including melanoma."