For the last 20 years, epidemiological data have suggested that sunscreen use could increase rather than decrease the risk of cutaneous melanoma. These observations contradict a vast body of laboratory experiments showing the ability of sunscreens to reduce many UV-induced skin lesions. The epidemiological studies have generally been criticized for being retrospective and possibly biased. In contrast, results from these studies were better accepted when they indicated that high nevi count and sunburn experience were risk factors for melanoma.
Autier P. Sunscreen and Melanoma Revisited. Arch Dermatol. 2000;136(3):423. doi: