By Genevra Pittman

NEW YORK (Reuters Health) - Girls who dress or act like boys and boys who act more feminine may be more likely to be abused and end up with post-traumatic stress disorder, suggests a new study.

Researchers said that parents or other adults who are uncomfortable with so-called gender non-conformity may treat kids differently -- sometimes violently -- or be convinced they can change their feelings and behavior.

"In some cases, they believe they're helping the child, that gender non-conforming won't be accepted by other people," said Andrea Roberts, from the Harvard School of Public Health in Boston, who worked on the study.

"But of course, abuse is never protective."

Roberts and her colleagues analyzed data from a long-term study on kids and teens who recalled their favorite toys, roles they took on during play and feelings of femininity or masculinity at age 11.

The participants were also asked about instances of abuse -- from kicking and grabbing to threatening to forced sexual contact -- that happened either before that time or during their adolescent years.

The researchers found that kids who were the most gender non-conforming were between 40 percent and more than twice as likely to report any kind of childhood abuse as those who did conform to typical gender roles.

They also reported more symptoms of PTSD, which include jumpiness, trouble sleeping and flashbacks.

Roberts said that while the findings can't prove that parents abused boys because they acted like girls and vice versa, the study did hint that gender non-conformity in younger kids predicted abuse during the teenage years.

The findings were published Monday in the journal Pediatrics, alongside another study in which doctors from Children's Hospital Boston report on their experience treating 97 kids and teens with gender identity disorder.

The disorder goes beyond not conforming to gender norms, and includes kids who are very bothered by their physical gender and identify as the opposite sex.

In that case, doctors can give younger kids hormones to slow down puberty, and older adolescents can begin the process of switching to the opposite gender by taking cross-sex hormones.

But before kids enter puberty, it's impossible to tell which ones will become more comfortable with their gender and which will have gender identity disorder, said Peggy Cohen-Kettenis, who works with these children and teens at VU University Medical Center in Amsterdam.

Forty-three of the kids treated at the Children's Hospital clinic had a history of psychiatric problems, including 20 that had self-harmed and nine that had attempted suicide.

Researchers led by Dr. Norman Spack pointed out that in kids who are already going through puberty and are serious about treatment, intervening at an early stage can keep them from developing secondary sex characteristics like facial hair and breasts, which may head off some of their distress.

"These are not girls who are doing boyish things that bother their parents, these are kids who are themselves unhappy with their own gender," Roberts told Reuters Health.

"If the kid is unhappy, depressed, troubled about their own body, that's probably (a sign) the parents could use some help."

She said that while adopting some opposite-gender behavior is relatively common, far fewer kids will be seriously bothered by their gender -- possibly about 1 in 1,000 --though researchers don't have a full grasp of the extent of gender identity disorder in children.

Those are the kids who may be at the highest risk of abuse and psychological problems, researchers said.

"Certainly when children grow up in an un-accepting environment, it's very likely that they are vulnerable for all types of abuse. It's not surprising," Cohen-Kettenis, who wasn't involved in the new research, told Reuters Health.

Other kids, she said, may just be more vulnerable and anxious than their peers if they're struggling with gender issues.

Researchers said that the most important thing for non-conforming kids, including those who are seriously questioning their own gender, is to get support from their families and schools.

"If a parent has a child who's gender non-conforming, they need to recognize that they're in a very powerful position to protect the child" with positive support, Roberts said.

SOURCES: http://bit.ly/xm2tBB and http://bit.ly/xyRShP Pediatrics, online February 20, 2012.