THURSDAY, June 6, 2013 (HealthDay News) -- Almost 30 percent of young children with autism also show signs of attention-deficit/hyperactivity disorder (ADHD), a rate that's three times higher than it is in the general population, a new study shows.
"We don't know the cause for ADHD in most cases. We don't know the cause of autism in most cases. It's not surprising that something that's going to affect the brain and cause one developmental outcome may also cause a second developmental outcome," said Dr. Andrew Adesman, chief of developmental and behavioral pediatrics at Steven and Alexandra Cohen Children's Medical Center in Lake Success, N.Y. He was not involved in the study.
Kids in the study who had both problems together also tended to have more difficulty learning and socializing than children who had autism alone.
The researchers noted that the treatment of ADHD may benefit children with autism if they aren't making progress with autism treatment programs, which often require sustained focus on specific skills.
"In a child [with autism] who has great difficulties with attention, or hyperactivity or both, you really have to layer in another level of intervention strategies for them," said study author Rebecca Landa, director of the Center for Autism and Related Disorders at the Kennedy Krieger Institute in Baltimore.
For the study, which is published in the June 5 online issue of the journal Autism, researchers asked parents of kids enrolled in a community-based study of child development about symptoms of attention and hyperactivity -- whether or not children could wait their turn, interrupted others who were speaking, fiddled with things during meals or could not slow down, for example. All the children in the study were between the ages of 4 and 8.
Out of 62 children diagnosed with autism, 18 (29 percent) also showed signs of ADHD.
A previous study of slightly older children found that 31 percent of children had the two disorders together.
"It's not surprising," said Dr. Patty Manning-Courtney, director of the Kelly O'Leary Center for Autism Spectrum Disorders at Cincinnati Children's Hospital Medical Center.
"What's good about this study is that they went to the trouble to look at who met diagnostic criteria and what was different about those children," said Manning-Courtney, who was not involved in the research.
All the children who had both problems together were boys. Boys have higher rates of autism and ADHD than girls, research shows.
One limitation of the study was that researchers had to rely on questionnaires that are meant to spot ADHD in typical children. There really aren't good tests for attention and hyperactivity developed for kids with autism, and their problems may look different than those seen in typical school-aged children.
Children who are higher functioning on the autism spectrum can have fairly obvious problems with attention.
"It's not that they have a deficit of attention. It's that they can't allocate their attention, or shift their attention to what it needs to be on," Manning-Courtney said. "I talk to parents of kids with autism about attention regulation more than attention deficit."
In children who are more severely autistic, ADHD can be harder to spot.
"It's hard to tell if their activity level is different because they're delayed or they're more severely autistic or if it's ADHD," Manning-Courtney said.
But if parents and teachers are noticing that attention or activity problems are interfering with a child's ability to make progress, that's the time to seek help, she noted.
First-line treatments for attention problems in kids with autism involve behavioral interventions that aim to teach kids to better control their focus.
If the behaviors don't get better with help, Landa said doctors will then move on to medication.
"If your child is having those kinds of problems, it's worth mentioning to the child's doctors and also touching base with the child's teachers," Landa said.
For more information on ADHD, head to the U.S. Centers for Disease Control and Prevention.