Teenagers are being "heavily exposed" to content featuring alcohol and tobacco in YouTube music videos, new research suggests.
Researchers stated teens exposed to these lyrics and images are "more likely to start smoking or drinking", which poses a "significant health hazard".
The study, published in the Journal of Epidemiology & Community Health, found 13- to 15-year-olds were most exposed and girls were exposed to more of these images and lyrics than boys.
"With these levels of exposure, in one year, music videos would be expected to deliver over four billion impressions of alcohol, and nearly one billion of tobacco, in Britain alone," the researchers wrote.
13- to 15-year-olds were most exposed to lyrics and images of alcohol and tobacco
Dr Amanda Gummer, child psychologist and founder of Fundamentally Children told HuffPost UK Parents that this could have a negative impact on teens.
"It’s vital that we give girls at this impressionable age good healthy role models to emulate," she said.
"It’s fruitless trying to regulate content on YouTube, the better approach is to ensure children and teens are getting a healthy amount of other off-line activities to balance screen time and find good role models in real life who will help them make informed decisions about their lives.
"It’s also important that we increase the media literacy of all children so they understand the difference between what they see on screen and real life, such as photoshopping, stage makeup and extreme clothing."
The study involved 2,068 teens and 2,232 adults
For the study, researchers used the results of two nationally representative online surveys of British adults and teens to calculate viewing figures for the 32 most popular music videos of top 40 chart songs in the UK, from 3 November 2013 to 19 January 2014.
To estimate the total number of "impressions" of alcohol and tobacco content, the researchers looked at each of the 32 videos in 10-second intervals, - a mention or image of alcohol or tobacco in any one of these intervals was counted as an "impression".
In all, 2,068 teens aged between 11 and 18, and 2,232 adults from the age of 19 onwards completed the surveys.
There was a total of 1,006 million impressions of alcohol and 203 million of tobacco during the period between release of the videos and the point of the survey.
Teens aged 13 to 15 received an average of 11.48 tobacco impressions, while those aged 16 to 18 received an average of 10.5. This compares with 2.85 for adults.
Exposure was 65% higher among girls, with the highest numbers of tobacco impressions delivered to 13- to 15-year-old girls.
An estimated 52.11 alcohol impressions were delivered to each teen compared with 14.13 to each adult. Exposure increased to 70.68 among 13-15 year old girls.
Songs delivering the highest tobacco impressions included 'Trumpets' by Jason Derulo and 'Blurred Lines' by Robin Thicke.
'Timber' by Pitbull and 'Drunk in Love' by Beyoncé, delivered the most alcohol content.
Researchers said teens exposed to alcohol and tobacco content in films are "more likely to start smoking or drinking". There were, however, no figures to support this claim.
Although a ban on paid-for placement of branded tobacco products has been in force since 2002 in the UK, no regulations apply to digital music videos.
Justine Roberts, Mumsnet's CEO told HuffPost UK Parents: "The internet presents really tricky parenting challenges, particularly if your own teenage years were more focused on Smash Hits than YouTube.
"There's a lot of dubious content and a lot of grey areas, particularly for older children and teens, and it can be hard to know just how concerned to be.
"Mumsnet users aren't complacent; there are loads of conversations about what's appropriate and how to navigate it, and how to try to enforce appropriate rules.
"Ultimately, the our users believe the best advice is to keep the lines of communication open and be on hand to advise and talk things through when needed."
Researchers urged: "Owing to the obvious health implications for adolescents, we suggest that overly positive portrayals of both alcohol and tobacco in music videos should be included in both the drug misuse and dangerous behaviour presented as safe rating categories."