Psychologists concluded that teenagers exposed to more sex on screen in Hollywood films are likely to have sexual relations with more people and without using condoms.
The study, based on nearly 700 popular films, found that watching love scenes could "fundamentally influence" a teenager's personality.
The researchers, from Dartmouth College in New Hampshire, concluded youngsters were more prone to take risks in their future relationships, the Daily Telegraph reported.
They also concluded that for every hour of exposure to sexual content on-screen, participants were more than five times more likely to lose their virginity within six years.
"Adolescents who are exposed to more sexual content in movies start having sex at younger ages, have more sexual partners, and are less likely to use condoms with casual sexual partners," Dr Ross O'Hara, who led the study, said.
"This study, and its confluence with other work, strongly suggests that parents need to restrict their children from seeing sexual content in movies at young ages," he said.
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The team, reporting in Psychological Science, studied 1228 children aged between 12 and 14 and then analysed their sexual behaviour six years later.
Each teenager identified which popular films of differing classifications they had seen from a random list of 50.
Six years later they were asked how old they were when they became sexually active, how many partners they had, how risky their sexual behaviour was and whether they used condoms.
The findings provided a link between exposure to sex on screen and sexual behaviour. Participants also said they tried to mimic love scenes they had seen on screen in the real world.
The researchers also assessed the sexual content of 684 of the biggest grossing films released between 1998 and 2004.
They found some of the most popular films from that time included scenes of a sexual nature, ranging from sexual scenes to heavy kissing.
These include Austin Powers, staring Mike Myers; Notting Hill, with Julia Roberts and Hugh Grant; American Beauty, staring Kevin Spacey and James Bond films such as The World is Not Enough, with Pierce Brosnan as 007.
A previous survey of films from 1950 to 2006 found that 84 per cent of movies contain sexual content.