A Molecular Perspective on Indoor Tanning and Melanoma Risk

Original Article : Molecular effects of indoor tanning

What are the key takeaways of this article?

Indoor tanning has been consistently associated with an elevated risk of melanoma, the most serious form of skin cancer. Despite longstanding public health warnings, the indoor tanning industry has maintained that tanning beds are comparable in risk to natural sunlight, often citing a lack of definitive molecular evidence. This retrospective observational study with case-control design incorporating molecular and genetic analyses, conducted by researchers at Northwestern University and UC San Francisco, addresses this gap, by providing biological evidence supporting distinct mechanisms through which indoor tanning may contribute to melanoma risk beyond those associated with natural sun exposure alone. 

Melanoma originates in melanocytes, the pigment-producing cells of the skin. Ultraviolet (UV) radiation-induced DNA damage within these cells can lead to the accumulation of mutations over time, ultimately resulting in malignant transformation. However, it has remained unclear whether artificial UV radiation induces distinct patterns of damage in melanocytes compared with natural sunlight, particularly in anatomical sites with limited habitual sun exposure. This question is clinically relevant, as tanning bed users, particularly young women, more frequently develop melanomas on the trunk and lower body, regions not typically associated with chronic sun exposure. Until recently, the molecular basis underlying this distribution had not been well characterized. 

In this study, the investigators enrolled over 32,000 patients, including patients with a quantifiable history of indoor tanning, controls who had never used tanning beds, and cadaver skin donors. They found that a history of tanning bed use was associated with a significantly increased risk of melanoma (odds ratio ~2.85), with evidence of a dose–response relationship. Melanomas in tanning bed users were more likely to occur on body sites with low cumulative sun exposure and were more frequently multiple primary tumors. 

At the molecular level, single-cell genomic sequencing from normal skin revealed that individuals with extensive tanning bed exposure had approximately double the mutation burden compared to controls, even exceeding that of older individuals without such exposure. These mutations included UV-associated mutational signatures and a higher prevalence of pathogenic and likely pathogenic variants in cancer-related genes. These effects were particularly pronounced in sun-protected areas such as the lower back, suggesting that tanning beds induce DNA damage in regions typically shielded by natural sunlight. In addition, melanocytes from tanning bed users were more likely to harbor pathogenic mutations associated with melanoma development, such as those impacting NF1 tumor suppressor genes. Most notably, tanning bed users in their 30s and 40s contained more melanoma-associated mutations than non-users in their 70s and 80s, indicating that tanning bed exposure accelerates aging by several decades.

These findings provide a molecular basis for why tanning bed users develop melanomas in less common anatomic locations, and challenge existing industry safety claims. For clinicians, these results reinforce the importance of counseling patients to strictly avoid tanning bed use, as well as obtaining a thorough tanning history in patients diagnosed with or at risk for melanoma. 

Publication date: May 25, 2026

Reference: Gerami P, Tandukar B, Deivendran D, et al. Molecular effects of indoor tanning. Sci Adv. 2025;11(50):eady4878. doi:10.1126/sciadv.ady4878

Summary by: Ella Liu