Teenagers felt more compelled to apply sunscreen if they saw in a video that it could protect their skin from premature aging than if they saw that it could protect against cancer, a new study shows.

"Vanity is more of a driving force to use sunscreen, as opposed to the fear factor of developing skin cancer," the study's lead author, William Tuong, told Reuters Health. Tuong is a fourth-year medical student at the University of California, Davis.

In his study, high school students applied sunblock three times as often if they watched a video showing how it could prevent their skin from wrinkling than if they watched a video showing how sun exposure causes melanoma.

Fifty Sacramento 11th-grade students participated in the study and saw one of two educational videos urging them to lather on sunscreen.

Tuong developed the five-minute videos to test the theory that teenagers were more likely to respond to messages about appearance than to messages about health.

A young, attractive woman speaks directly to youth in both videos.

In one, the actress emphasizes the growing incidence of melanoma in young people and the link between the deadliest form of skin cancer and ultraviolet light. In the other video, the same actress discusses how ultraviolet light contributes to premature aging and "can make you look older and less attractive."

"We are not trying to look like our grandparents, right?" the actress says. "Have you seen what the sun can do to a grape? It gets shriveled and wrinkled. Raisins are not cute," she says.

"I don't want to look like a raisin face, and I don't think you want to either," she continues. "The sun causes wrinkles, dark spots, uneven skin tones, sagging skin and rough, leathery skin. These are all the things that will make you look older and definitely less sexy."

The video teaching the kids to use sunscreen to prevent skin cancer sounds more clinical, like a biology lecture.

The researchers assessed how often students applied sunscreen before watching the videos and six weeks after.

Students who saw the appearance-based video went from using sunscreen an average of 0.6 times a week to 2.8 times a week. Those who saw the video stressing health benefits, however, increased their average usage by only a fraction of a day - from 0.7 to 0.9 times a week, according to findings published in the Journal of the American Academy of Dermatology.

The researchers also tested students' knowledge about proper sunscreen use and the effects of exposing their skin to the sun before and after they showed the video. After watching the videos, students in both groups improved their knowledge about the benefits of using sunscreen.

The study provides evidence that appearance-based messages may be better than traditional health-based messages in promoting sun-protection measures, the authors say.

Prior research has shown that efforts to educate kids about sun exposure and skin-cancer risk have improved knowledge but failed to improve sunscreen usage.

"Past research shows that adolescents have difficulty practicing preventive health behavior because they believe themselves less likely to experience disease," the authors of the current study write.

One prior study did find that college students significantly increased their sunscreen use after seeing ultraviolet-filtered photographs of their faces.

Tuong said videos are substantially less expensive to produce and easier to distribute than ultraviolet-filtered photographs.

"Video definitely could be used in a clinic setting, in the waiting room or in an office while a student is waiting," he said.

"With younger individuals, messages that resonate with them are messages that speak to them now," Tuong said. "Appearance-based messaging resonates with them because it's more about short-term risk versus long-term risk."

The health-based video can be seen here: bit.ly/1oc0hMp and the appearance-based video here: bit.ly/1dCLiCh.