Magazines, television, video games and music videos all have a detrimental effect, a task force from the American Psychological Association reported.
Sexualisation can lead to a lack of confidence with their bodies as well as depression and eating disorders.
Such images also have a negative effect on healthy sexual development in girls, the researchers said.
The task force was set up after mounting "public concern" about the sexualisation of young girls.
Research on the content and effects of television, music videos, music lyrics, magazines, films, video games and the internet was analysed.
Recent advertising campaigns and merchandising of products aimed at girls was also scrutinised.
Sexualisation was defined as occurring when a person's value comes only from her or his sexual appeal or behaviour, to the exclusion of other characteristics, and when a person is portrayed purely as a sex object.
They gave examples of a trainer advert that featured pop star Christina Aguilera dressed as a schoolgirl with her shirt unbuttoned, licking a lollipop.
According to the research identified by the task force, such images and promotion of girls as sexual objects negatively affects young girls in many ways.
We need to replace all of these sexualised images with ones showing girls in positive settings - ones that show the uniqueness and competence of girls
Dr Eileen Zurbriggen Task force chair
"The consequences of the sexualisation of girls in media today are very real," said Dr Eileen Zurbriggen, chair of the group and associate professor of psychology at the University of California, Santa Cruz.
"We have ample evidence to conclude that sexualisation has negative effects in a variety of domains, including cognitive functioning, physical and mental health, and healthy sexual development."
The task force called on parents, school officials, and health professionals to be alert for the potential impact on girls and young women.
And it advised that schools should teach pupils media literacy skills and should include information on the negative effects of images portraying girls as sex objects in sex education programmes.
Governments also had a responsibility to reduce the use of sexualised images in the media and advertising, they said.
Dr Zurbriggen added: "As a society, we need to replace all of these sexualised images with ones showing girls in positive settings - ones that show the uniqueness and competence of girls.
"The goal should be to deliver messages to all adolescents - boys and girls - that lead to healthy sexual development."
Professor Andrew Hill, professor of medical psychology at the University of Leeds, said it was hard to disagree with any of the reports conclusions.
"If you look at teenage magazines, it's all about sex.
"We are a visually absorbed society - our views of people are dominated by how they look."
He added that the use of women as sex objects in the media and advertising was a difficult issue to deal with.
"Only 18% of children's television viewing is in their designated viewing time and legislation can't be the answer for everything.
"One of the key things here is social responsibility - advertisers and other media need to be aware that the products they produce and images associated with them have an impact and it's not always a good impact," he said.