Updated

The pressure to act grown up and be sexual is damaging teen and 'tween girls psychologically, a United Kingdom study released Monday has found.

Girls as young as 10 are being harmed by sexually charged advertisements and magazine images, the study concluded.

The pressure has led to self-harming and has made young girls feel as though they must wear clothes that made them look older. Girls also say they must increasingly deal with sexual advances from boys, according to the study by Girlguiding U.K., which is similar to the Girl Scouts.

Sexual pressure on teens is also a problem in the U.S. A study from a division of the National Institutes of Health released last week found that the number of teens having sex is relatively unchanged but teen pregnancy is up for the first time in 15 years.

Dr. Keith Ablow, a psychologist and FOX News contributor, said last week that images of teen sexuality in the media are giving youths the wrong idea.

"As long as we continue to see images of Jamie Lynn Spears glamorizing teen pregnancy when she releases her baby pictures to magazines, talking about how wonderful it is and saying nothing about any difficulties, teens are going to view this as a positive and defining moment of their lives," Ablow said. "A lot of teens will look at this and say 'we’ve been lied to.' They're going to believe you can have a baby and feel loved and you can have sex now. There's no reason to wait."

The U.K. study, called "A Generation Under Stress?," was based on focus groups involving 54 girl guides between the ages of 10 and 14, as well as an online survey of 350 girls aged 10 to 15.

Girls surveyed said that magazines and Web sites directly targeting young girls with messages that they should lose weight, wear make-up and even consider plastic surgery are particularly damaging to their mental health.

“When I was 11, I read a teenage magazine for the first time and that is when it kind of clicked, ‘I should be like this,’” one respondent wrote of the images she saw in the magazine.

Two-fifths of those surveyed knew someone who had self-harmed, and almost the same number knew someone who experienced panic attacks due to the pressure to emulate what they see in magazines.

A third of those questioned said they had a friend with an eating disorder.

Ablow explained that images of teen sexuality such as the controversial advertisements run by high school TV drama "Gossip Girl" last April, which depicted various teen characters having sex, as well as the shocking Vanity Fair photo of 15-year-old Miley Cyrus wearing nothing but a sheet, are increasingly gaining acceptance in society.

This weekend, celebrity blog, justjared.com, posted a picture of Cyrus showering in a wet T-shirt, and earlier this year private photos of a nude "High School Musical" star Vanessa Hudgens, 19, were leaked online and run on several blogs.

"When you live in a society in which Hugh Hefner sees no problem in offering Miley Cyrus a chance to pose in Playboy you're going to see the age of initiation into sex continue to plummet," Ablow added. "You're also going to see the rate of teen pregnancy skyrocket and accessory problems such a substance abuse and depression spin out of control."

Click here for the full study from Girlguiding U.K.