Teenagers who exchange digital messages with sexual content, a practice known as sexting, are more likely to experience violence in love relationships, a study has found.

In a survey of more than 1,000 14 to 17-year-olds in Norway, 549 reported having had a romantic partner.

Nearly a third of the young lovers said they had sent explicit sexual messages -- pictures and/or text -- to their sweethearts.

Compared to teens who had not engaged in sexting with a partner, these adolescents experienced four times more physical violence -- acts such as smacking, pushing, strangulation or being beaten with a hard object, the researchers found.

They suffered 2.5 times more sexual abuse, ranging from forced kissing to rape, and 3.5 times more psychological violence.

The findings were reported in the peer-reviewed Scandinavian Journal of Public Health.

For teens, "there is a bigger chance of becoming a victim of intimate partner violence if you send messages with sexual content," said lead author Per Hellevik, a sociologist at the Norwegian Centre for Violence and Traumatic Stress Studies is Oslo.

More than 40 percent of youngsters with love interests -- which did not necessarily include sex -- said they had experienced couple violence of some kind. This included sexters and non-sexters.

Girls were far more exposed to violence than boys, the study showed, especially those with older partners.

They also reacted differently.

Both sexes were asked how they felt when subjected to violence in a relationship, with possible answers ranging from "sad" and "frightened" to "loved" and "desired".

Twice as many girls expressed negative feelings about violence.

At the other extreme, "one percent of the girls and 35 percent of the boys had purely positive experiences", Hellevik said in a statement.

The study does not conclude that sexting causes violence, noting that children who experience fighting or brutality at home or at school are prone to similar behaviour with their intimate partners.

Sexting, in other words, could be as much symptom as cause.

The findings raise thorny questions about when parents and teachers should intrude in the private digital lives of youngsters.

"We wouldn't let teenagers hang around in the streets all day without knowing what they are up to or who they were with," said Hellevik.

"In the same way, they shouldn't be allowed to hang around online on their own."