The sunscreen-causes-melanoma scare does not survive the data

Sunscreen was developed to prevent sunburn and has long been assumed to protect against skin cancer as well. Yet the published literature contained conflicting results, including reports claiming that sunscreen users had higher rates of melanoma, a claim with obvious power to change public behaviour. Nobody had rigorously weighed the whole body of evidence to test how strong and consistent those associations really were. This review set out to do exactly that, and to explain why studies disagreed.

The authors searched MEDLINE for every article published between 1966 and 2003 reporting on sunscreen use and melanoma in humans, keeping analytic studies where sunscreen use was recorded before diagnosis. Two reviewers independently extracted the data, re-reviewing inconsistencies until they agreed, with a third party resolving any remaining discrepancies. Odds ratios from 18 studies were then pooled using standard statistical techniques, and the authors examined whether risk changed with frequency of use or with years of use.

Pooled across 18 studies, ever using sunscreen showed no association with melanoma. The variation between individual studies was explained by those that failed to adjust for sun sensitivity: people who burn easily both use more sunscreen and develop more melanoma, which can make the product look guilty by association. There was also no dose-response pattern, with risk unchanged whether people used sunscreen never, sometimes or always, and unchanged by years of use. That flat pattern is further evidence that the true association is null.

The finding directly contradicts earlier reports linking sunscreen to melanoma and offers a tidy explanation for them: confounding by sun-sensitive skin rather than any effect of the product. It does not, however, demonstrate that sunscreen protects against melanoma either, and the authors note it may take decades of follow-up before any protective effect of newer formulations becomes detectable. The evidence here comes entirely from studies observing people's habits, not trials assigning sunscreen use. So the harm question is answered more convincingly than the benefit question.

If you have ever hesitated over claims that sunscreen causes melanoma, this pooled analysis is a reason to set that worry aside: the scare traces to a statistical artefact, not the cream. At the same time, this analysis alone cannot tell you sunscreen prevents melanoma, since that answer needs longer follow-up of modern formulations. The practical picture stays what sunscreen was designed for, protection against sunburn, with the cancer scare removed from the ledger.