Researchers published an article in the Journal of the American Medical Association supplement Internal Medicine in June, suggesting that Viagra can increase a person’s risk of developing melanoma, though researchers are reluctant to make more concrete assertions.

According to the Viagra melanoma paper, researchers found that taking Viagra correlated with an 84 percent increase in the risk of developing melanoma. The study worked by analyzing medical data from more than 26,000 men.

Using this data, researchers used statistical analysis to parse out connections between Viagra and possible Viagra side effects. Statistical analysis consists of using mathematical equations to calculate how closely two variables match up to each other and how likely it is that these connections (or correlations in statistical terms) are truly linked and not just coincidence.

The Viagra melanoma study made several interesting findings. First, researchers tested the idea that cofounders could produce the result. Cofounders are variables that relate to the subject of a research study and produce confusing results.

For example, researchers performed a statistical analysis to see if patients with erectile dysfunction were more likely to suffer from melanoma independently from taking Viagra. According to their analysis, this was not correlated, suggesting that erectile dysfunction itself was not acting as a cofounder.

Additionally, researchers looked for a link between Viagra and other types of skin cancer. Researchers found that Viagra was not associated with an increased risk of other types of skin cancer. This specificity supports the idea of a Viagra melanoma link.

Researchers proposed a possible mechanism that could explain how Viagra could theoretically promote melanoma. Viagra could interfere with a certain class of chemicals the body produces to discourage tumor formation and growth.

Without these chemicals, it could be easier for melanoma to get a foothold in the body. While researchers did not study this specific mechanism, the description lends biological plausibility to their hypothesis that Viagra can cause melanoma.

Researchers were careful to state that this type of study cannot prove that Viagra causes melanoma. This type of study is strictly observational, and it will require further research to more firmly establish that Viagra is one of the causes of skin cancer. However, the authors of the paper felt that their results warranted further investigation into a possible Viagra melanoma risk.

While researchers were careful not to overstate their case, researchers did propose “a longer and detailed follow up with more detailed assessment.” Such a study could look at how much Viagra patients took. If patients who took more Viagra developed melanoma more often, this could suggest dose-dependence. In epidemiological research, dose-dependence is seen as a good indicator that a drug and a side effect are related.