THURSDAY, Sept. 15 (HealthDay News) -- Children with attention-deficit hyperactivity disorder (ADHD) are twice as likely to be injured badly enough to need medical attention as other children are, a new study finds.

More than 5 million U.S. children, or about 9.5 percent, have been diagnosed with ADHD as of 2007, according to the U.S. Centers for Disease Control and Prevention. Kids with the condition act impulsively, have difficulty paying attention that often affects their ability to succeed in school and, in some cases, are physically hyperactive.

In the study, researchers analyzed data from questionnaires filled out by the parents of 4,745 fifth graders in Houston, Los Angeles and Birmingham, Ala. that assessed ADHD symptoms.

Though the questionnaires were not official ADHD diagnoses, researchers said that children who scored high on the ADHD assessment are likely to have ADHD.

The parents of children who scored in the 90th percentile for symptoms of ADHD were nearly twice as likely to report their child had been injured in the previous year than the parents of kids in the lowest percentile (10th percentile) for ADHD symptoms.

"ADHD is a disorder that's associated with impulsive behaviors -- children do things without thinking. It's associated with inattention -- they're not really paying attention to risks in their environment. And it's associated with executive function -- planning ahead, thinking ahead and having inhibition when you need it," explained study author David Schwebel, director of the University of Alabama at Birmingham's Youth Safety Laboratory. "Children with ADHD are poor at those skills, and that combination of things is leading them to take risks and behave impulsively, which leads to getting hurt."

The study is published in the September/October issue of Academic Pediatrics.

Parents were also asked to rate their child on symptoms of conduct disorder, or a pattern of defiant, antisocial and aggressive behavior. Children who scored in the 90th percentile for symptoms of conduct disorder -- a condition often marked by rule-breaking, bullying, property damage, hurting animals and/or other violations of social norms -- also had 1.5 times the risk of injury as kids in the 10th percentile. However, after researchers adjusted for other variables, only ADHD symptoms were significantly associated with injury.

Some children have both ADHD and conduct disorder, researchers said, and the symptoms can overlap. Further analysis showed that ADHD symptoms such as impulsivity are more strongly associated with injuries than the defiant behavior associated with conduct disorder. In addition, there was no statistically significant interaction between ADHD and conduct disorder.

"You're supposed to look before you leap. Kids with ADHD are leaping before they look," said Alan Delamater, a professor of pediatrics and psychology at University of Miami Miller School of Medicine.

In the study, about 10 percent of kids had one injury during the prior year, 3.5 percent had more than one injury and 86 percent were not injured.

Types of injuries included broken bones (52 percent), sprains/strains (15 percent), and cuts/bruises (15 percent). Boys were more likely to be injured than girls, and white children were more likely to suffer injuries than Hispanic children.

While spending soccer season or summer vacation in a cast is no fun for a kid with ADHD, it's the even more serious risk taking that parents have to worry about the most, Schwebel said.

Injuries are the leading cause of death for 11-year-olds; although many of those deaths are caused by motor vehicle accidents, not all are.

A recent study by Schwebel's team found that children with ADHD are more likely to take risks when crossing the street. While the kids with ADHD were just as likely to remember to look both ways when put into a simulated street crossing, they tended to dart across the road leaving less time to spare in front of oncoming traffic and having more close calls.

"You're going to see kids with ADHD taking risks. When it becomes scary is when they dive into the pool headfirst, or they dart across the street and get hit by a car," Schwebel said.

Still other research has found that teens with ADHD are more likely to get into car accidents, Delamater said.

So what should parents do?

Awareness that a child with ADHD is at higher risk of injury is important, experts said. "The parents of kids who demonstrate these symptoms need to be even more vigilant in terms of injury prevention, and primary care doctors need to counsel parents about the increased risk," Delamater said.

That, of course, gets more difficult as children get older and aren't always in sight of mom and dad, so it's also important to get help for the disorder, Schwebel said. Psychotherapy and medications have both been shown to curtail symptoms.

And though easier said than done with kids with ADHD, as much as they can, "parents need to teach children to be cautious, to think about what they're doing and to recognize situations than can be dangerous," he added.

More information

CHADD has more on ADHD.