"We were very surprised to find that so many did it," said lead researcher Tove Grenklo, a behavioral scientist at the Karolinska Institutet in Stockholm.
Cutting and burning is thought to be how some troubled teens express their emotions, according to the American Academy of Child and Adolescent Psychiatry. Those teens may hurt themselves if they can't talk about their feelings, are upset or have low self esteem.
Earlier this year, a study found that children start harming themselves as early as third grade.
The study's researchers write in the Archives of Pediatrics and Adolescent Medicine that past research showed children with one dead parent are already more likely to have - among other things - psychiatric problems, depression, drug and alcohol abuse and anxiety.
Grenklo and her colleagues wanted to see if they were also more likely to hurt themselves.
For the study, they used Sweden's national death databases to find and survey teens who lost one of their parents to cancer between 2000 and 2003, when they were between 13 and 16.
They then found teens who still had two living parents for a comparison group.
Of the 851 teens who lost a parent, 622 returned their survey, as did 330 of the 451 teens in the comparison group.
Overall, about 20 percent of the teens with only one surviving parent said they hurt themselves, compared to about 10 percent of teens with both parents living.
'WE SHOULD TALK WITH EACH OTHER'
"This study is one of the first to establish that (losing a parent to cancer) might be a unique risk factor for this behavior," said Stephen Lewis, who was not involved with the new study but has studied self-injury at the University of Guelph in Ontario, Canada.
Lewis added that the study's findings seem to be in line with other estimates of how many teens injure themselves.
The researchers say teens may be driven to self-injure after their parents' deaths by an increased sense of emotional distress and numbness.
Another possible explanation for the increase is that the teens lost a caretaker who would notice their emotional suffering and prevent self-injury, they add.
As for prevention, both Grenklo and Lewis emphasized communication.
"I'm a strong believer that we should talk with each other," said Grenklo. "Children need to know the facts of what happened and why. And that it's OK to be sad and talk about the diseased parent."
"We know one of the reasons people self injure is that they use injuring as a way to release their emotions," said Lewis, who added that it's important for parents, family members and teachers to know how to talk about self-injury and how to prevent it.
Lewis said information on preventing and handling self injury can be found at SIOutreach.org - a Web site where he is co-director.