A new study found that use of Viagra is linked to an increased risk of melanoma, a deadly form of skin cancer. The study was published on April 7, 2014 in JAMA by researchers at the Harvard Medical School. Viagra may stimulate the synthesis of the skin pigment melanin which has been linked to increased melanoma risk. The study did not include other erectile dysfunction drugs but researchers noted the risk might include Cialis and Levitra as well.