A 2014 study linking the active ingredient in Viagra and the deadly skin cancer melanoma caused a stir in the media.

The initial study was published in the American Medical Association’s peer-reviewed journal JAMA: Internal Medicine. The article described prospective cohort study, a type of epidemiological study in which researchers find similar groups of people that vary in on or two factors and follows them for a time, typically several years, to see if they have different health outcomes.

In this case, researchers investigated the health of 25,848 men through health questionnaires and further medical tests in some cases. It was found that men taking Viagra had a higher rate of melanoma than their peers. This study found that Viagra was not linked to other types of skin cancer, and that men with erectile dysfunction not taking Viagra did not have an increased rate of melanoma.

Several media outlets picked up the story and spun it slightly differently in each case.

Fox News was somewhat laid back, stressing that the study was preliminary and that there was no cause for panic. They did take the time to translate the study’s statistics into more concrete numbers, saying that the data could represent one extra case of melanoma per 1,000 men.

The Fox News report also stated that many men with erectile dysfunction do not need Viagra long-term, as erectile dysfunction is often a symptom of other conditions, which can be treated and controlled.

NBC’s website also covered the JAMA study. Their article repeated the study’s statistic that men taking Viagra had an 84 percent higher rate of melanoma. Like Fox, NBC’s article stated that the study was preliminary and not a cause for panic. They did quote recommendations from the paper that men taking Viagra touch base with their doctors more often to head off any melanoma concerns.

Even Harvard Men’s Health Watch weighed in on the JAMA paper, cautioning that the media may have been premature in interpreting the study.

While Fox and NBC both mentioned that the study was preliminary, the Health Watch article actually explained why. Prospective cohort studies are inherently observational rather than experimental.

In this type of study, there is always a chance that the correlation between cause and effect could be the result of an ambiguous variable called a cofounder, an additional variable that researchers haven’t accounted for.

Despite some controversy, a class action lawsuit investigation has been launched to explore the possibility of legal action over the alleged link between Viagra and melanoma. Such a lawsuit could allege that drug makers were aware of the alleged risk between Viagra and melanoma, but aggressively marketed the drug anyway, endangering the public.