By Lynn Nguyen, M.D. :

"Mom, he's picking on me!"

With summer here and family road trips underway, it's a phrase that parents may be hearing more and more from the back seat. More often than not, parents dismiss this kind of sibling bullying as harmless. Recent research begs to differ.

Researchers at the University of New Hampshire conducted more than 3,500 telephone interviews with children and teenagers (an adult caregiver was interviewed if the child was younger than 10). The researchers asked these kids whether they had experienced physical assault, property damage or "psychological aggression" - in other words, name calling, meanness and ostracism.

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Kids and teens on the receiving end of sibling bullying did, indeed, experience mental distress from teasing and aggression.

Interestingly, they found that even mild bullying - a punch once in a while - could be detrimental. Victims still reported mental distress at a greater rate than their unbothered counterparts. The youngest victims appeared to be at the highest risk of mental health effects from this less severe aggression; the study found that in the case of mild physical assault, the younger ones under the age of 9 reported greater mental health distress than kids aged 10 to 17.

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Among all age groups, even those who didn't suffer the whole gamut of aggressive acts from a sibling, were still affected.

"Even children who experienced just one type of sibling aggression had worse mental distress than with a child who experienced no sibling aggression," said study author Corinna Tucker at the University of New Hampshire Family Studies and sociology department.

"There has been a lot of work to prevent or stop aggression for peers, but not much is seen for sibling aggression."

Dr. Robin Mallett, a child and adolescent psychiatrist of the University of Texas Medical Branch in Galveston, believes this study "shines light on a type of maltreatment that many believe to be a benign part of growing up."

"The parental reaction to a child being bullied by nonfamily members may be quite different from that of a sibling aggressor, which may be particularly distressing for the bullied child," she said.

If you're thinking back on your childhood and wondering if there's a child who wasn't bullied by a sibling, it raises the question: What can parents do?

Being aware of the consequences is a big step. Mallett advises parents that they "must provide developmentally appropriate supervision of children and to communicate that no bullying is acceptable, even by siblings, and that parents are available to help them with such serious matters." Here's how:

Establish values and rules: Bullying is not tolerated;

Don't exhibit aggressive behavior yourself, particularly when your children are around;

Reward positive behavior and kindness between siblings;

Acknowledge and praise individual traits of each child;

Do not "play favorites" among your children;

Take time to build the self-esteem of each child;

Give your children time apart during conflicts to defuse situations.

Mallett added that parents should not hesitate to seek advice from child and adolescent psychiatrists or pediatricians regarding the needs of the bullied child - as well as that of the bully - since both children may benefit from professional intervention.