And those language difficulties can have far-reaching academic consequences, the study found.
The study, published online April 21 in Pediatrics, looked at 6- to 8-year-olds with and without ADHD in Australia.
"We found that 40 percent of children in the ADHD group had language problems, compared to 17 percent of children in the 'control' group," said Emma Sciberras, a clinical psychologist and post-doctoral research fellow at the Murdoch Children's Research Institute in Victoria, Australia.
"Rates of language problems were similar in boys and girls with ADHD," she added.
The impact that language problems might have on these factors hasn't been well-studied, the study authors noted.
"The differences in academic functioning between children with ADHD and language problems, compared to those with ADHD alone, were quite large and clinically meaningful," said Sciberras.
Language problems refer to spoken language—both receptive and expressive language. Receptive language is the ability to listen and understand what's being said; expressive is the ability to speak and be understood.
In a separate study in the same issue of the journal, Sciberras and her colleagues looked at almost 400 children with ADHD, aged 5 to 13, and found almost two-thirds had one or more anxiety disorders.
When children with ADHD had two or more anxiety disorders—this was true for one-third of the kids—their quality of life, behavior and daily functioning suffered, the researchers said.
"It is very common for children with ADHD to experience additional difficulties," said Sciberras. "Both of these studies demonstrate that the additional difficulties that go along with ADHD, in this case anxiety and language problems, can make daily functioning even harder for children with ADHD."
The language study included 179 children diagnosed with ADHD and 212 without the attention disorder. Fewer than half of the children with ADHD were taking medications to help control their symptoms.
After adjusting for sociodemographic factors and other conditions, such as autism spectrum disorders, the researchers found that the risk of language problems was 2.8 times higher in children with ADHD.
When the researchers looked at how those language problems affected school work, they found lower math, reading and academic scores.
However, the researchers didn't find that language problems had an impact on social functioning.
"We were surprised that language problems were not associated with poorer social functioning for children with ADHD," Sciberras said.
"It could be that children with ADHD are already experiencing poorer social functioning due to other factors including their ADHD symptoms or other associated difficulties."
However, Sciberras cautioned that language troubles might become more problematic as these kids get older because social relationships get more complex with age.
One outside expert said the study is a good reminder for parents and physicians.
Whether speech-language interventions will help the youngsters with ADHD isn't clear, however.
Berg also pointed out that this issue is a "chicken-and-egg" problem.
He said "We don't know if these kids have;
- a language disorder that's causing them to not understand what's going on at school
- and that's making them restless and fidgety because they're bored
- Or do they have ADHD and that's causing difficulty understanding the language.
- Or is there something going on in an area of the brain that creates both of these problems?
It's possible that the findings from this Australian study might not translate to a U.S. population.
For one thing, medication trends might differ, Berg said. For children with ADHD who also suffer anxiety, Sciberras said medications might help, and a type of psychotherapy called cognitive behavioral therapy could also be useful.
The researchers are currently conducting a study to treat anxiety in children with ADHD.
"If parents are concerned that their child with ADHD has anxiety, language or any other additional difficulties that are not currently being managed, we encourage them to discuss their concerns with their child's treating clinician," she said.