A new study reports that using tanning beds is associated with nearly triple the risk of melanoma and with pervasive DNA damage across the skin, including in areas that are usually protected from the sun. Researchers from Northwestern University and the University of California, San Francisco, examined medical records and carried out genomic analyses to reach these conclusions. The findings, published on December 12 in Science Advances, are prompting calls for stronger public health warnings against indoor tanning.
Researchers have detailed how tanning beds contribute to melanoma, the deadliest form of skin cancer and a disease responsible for an estimated 11,000 deaths annually in the United States, according to the new study in Science Advances and related institutional summaries.
The research, co-led by Dr. Pedram Gerami of Northwestern University Feinberg School of Medicine and Dr. A. Hunter Shain of the University of California, San Francisco, included an epidemiologic analysis of about 3,000 people with a documented history of indoor tanning and roughly 3,000 age‑matched individuals who had never used tanning devices. Melanoma was diagnosed in 5.1% of tanning‑bed users versus 2.1% of non‑users, corresponding to a 2.85‑fold higher risk of melanoma for indoor tanners even after adjusting for age, sex, sunburn history and family history of melanoma, according to Northwestern’s report on the study.
To investigate the biological basis of this risk, the team used single‑cell DNA sequencing on melanocytes, the pigment‑producing skin cells where melanoma begins. In total, the researchers sequenced 182 melanocytes from skin samples drawn from three groups: 11 patients from Gerami’s clinic with long histories of indoor tanning, nine individuals who had never used tanning beds, and six cadaver donors who served as additional controls. Melanocytes from tanning‑bed users carried nearly twice as many genetic mutations as those from the control groups and more often harbored pathogenic, melanoma‑associated mutations, the authors report.
Crucially, the excess mutations were not confined to frequently sun‑exposed sites. The study found that tanning‑bed users were more likely to develop melanoma, and to carry heavy mutation burdens in melanocytes, on body areas that usually receive little natural sunlight, such as the lower back and buttocks. This pattern supports the conclusion that tanning beds can mutagenize a broad field of skin, extending beyond the areas typically damaged by ordinary sun exposure.
"Even in normal skin from indoor tanning patients, areas where there are no moles, we found DNA changes that are precursor mutations that predispose to melanoma," Gerami said in a statement released by Northwestern University. He noted that he has observed this clinical pattern over two decades of treating patients, including many younger women with multiple melanomas who reported frequent indoor tanning.
One study participant, 49‑year‑old Heidi Tarr from the Chicago area, began using tanning beds two to three times a week as a teenager, influenced by peers and beauty trends. In her 30s, she was diagnosed with melanoma on her back and underwent surgery followed by years of monitoring and more than 15 additional biopsies, according to Northwestern’s account. Tarr agreed to donate skin biopsies for the research, saying she hoped that sharing her experience and tissue samples would help others better understand the risks of indoor tanning.
Drawing on the new molecular and clinical data, Gerami argues that indoor tanning should at minimum be prohibited for minors and that tanning devices should carry warning labels similar to those on cigarette packages. He points out that the World Health Organization’s International Agency for Research on Cancer classifies tanning beds as Group 1 carcinogens, the same category as tobacco smoke and asbestos. The authors also recommend that people who have frequently used tanning beds in the past receive a total‑body skin examination from a dermatologist and discuss the need for ongoing skin checks.
The study, titled "Molecular effects of indoor tanning," was published December 12, 2025, in Science Advances. According to Northwestern and UCSF, it was supported by grants from the National Institutes of Health, including the National Cancer Institute and the National Institute of Arthritis and Musculoskeletal and Skin Diseases, the Department of Defense Melanoma Research Program, the Melanoma Research Alliance and several additional philanthropic and institutional funders.
