Frequent tanning bed users may have up to an eight times greater risk for melanoma than people considered at high risk for melanoma who don’t use tanning beds, according to a new study that also showed how tanning beds alter melanoma-linked DNA on the molecular level and damage areas of skin not usually exposed to the sun.

A case-control cohort study of patients considered at high risk for melanoma finds that tanning bed users have higher rates of melanoma and disease with significantly more mutations.