Children with attention deficit hyperactivity disorder (ADHD) who sustain mild traumatic brain injury (mTBI) such as concussion are more likely to be moderately disabled after injury than those who sustain mTBI without ADHD, finds a new study [1], which suggests that children with ADHD be encouraged to avoid contact sports that put them at increased risk of TBI. 

Researchers at Children's Hospital of Pittsburgh and the University of Chicago reviewed the charts of all patients with diagnosis of mTBI as a result of closed head injury (CHI) and ADHD admitted to the hospital between 2003 and 2010, and compared them to a control group of patients admitted with a diagnosis of CHI without ADHD.  The most common causes of injury for the ADHD group were falls (17%), pedestrian versus car (15%), blunt object to head (15%), bicycle accidents (13%) and sports accidents (12.5%). In the control group, the most common injury mechanisms were falls (20%), motor vehicle collision (16%), all-terrain vehicle accident (16%), and blunt object to head (13%).

They found that outcomes for the ADHD patients were significantly worse than for those without ADHD, even when adjusting for sex, age, initial Glasgow Coma Scale score, length of hospital stay, mechanism of injury, and presence of other (non-TBI) injuries:

• After a mild injury, 98% of the control patients were back to baseline functioning and 84% had recovered completely with no complications by the last follow-up (mean 7.2 weeks) while 25% of the mild CHI patients with ADHD were still moderately disabled (mostly independent but needs degree of supervision/actual help for physical or behavioral problems, or is age-appropriately independent but has residual problems with learning/behavior or neurological effects affecting cognitive function) at follow-up; and
• Only 56% of the mild CHI patients with ADHD had a complete recovery, even after a statistically significantly longer follow-up (mean 25 weeks) compared to 84% in the control group. 

Reasons for increased risk of disability unclear 

"There are numerous explanations for these data," wrote Christopher M. Bonfield, MD, of the Department of Neurosurgery at Children's Hospital of Pittsburgh, including:

• children with ADHD may be more vulnerable to brain injury;
• ADHD may impair the healing process;
• rehabilitation programs may be less effective for children with ADHD;
• at baseline, children with ADHD may be more disabled than their peers, and so comparisons on a outcome scale for childhood head injury (KOSCHI or King's Outcome Scale for Childhood Head Injury [2] will find more disability in the ADHD group after TBI;
• TBI may unmask characteristics of pre-existing ADHD leading to the appearance of new symptoms (Bonfield acknowledged that "fundamentally, we cannot distinguish whether a 'new' disability after TBI was due to the TBI or to an unmasked symptom of previously diagnosed ADHD);
• socioeconomic status (SES) predicts worse outcomes after TBI, noting that there is an association between lower SES and the incidence of ADHD, and that it was possible that ADHD was acting in the study as a "proxy for low SES, and that low SES, not ADHD, is leading to worse outcomes after TBI," although Bonfield and his colleagues noted that the magnitude of the outcome disparity after TBI between the ADHD and non-ADHD group in their study was larger than that reported in previous studies; and/or
• TBI may have caused an ADHD-like syndrome called sADHD, noting that there was data suggesting that children with ADHD are more likely to develop sADHD after TBI.

Should kids witih ADHD avoid contact sports? 

The study is significant in four ways, says Bonfield:

1. It "highlights the importance of preventing TBI in children with ADHD, perhaps by encouraging them to avoid contact sports or hobbies that carry an increased risk of TBI. This is especially pertinent given data that children with ADHD are reported to sustain higher levels of injury, especially CHI, when compared to age-matched controls."  
2. It "may better inform clinical management in children who have ADHD and experienced a mild traumatic brain injury, "perhaps directing more intensive resources and closer monitoring to encourage maximal recovery."
3. It may "spur the education of families of children with ADHD about expectations during the recovery period after TBI.
4. It provides "another reason to be aggressive about effective ADHD treatment, as data shows that children who are effectively treated do as well in life as those without ADHD."

Minimizing risk 

The takeaway message for parents, says Rosemarie Scolaro Moser, Ph D, MomsTEAM's expert sports concussion neuropsychologist and Director of the Sports Concussion Center of New Jersey, is "that ADHD is another risk factor that should be considered in contact/collision sports. All kids need exercise, all kids benefit from sports, all kids are at risk for concussion. The parent's job is to minimize that risk."

"There is no clear evidence that says a child with ADHD should not play hockey, football, lacrosse or skateboard, ski, or play any other sport. But parents should be wise in considering all risk factors, whether ADHD, gender, history of headaches, number of previous head injuries/concussions, age and any other modifying factors [including an overly aggressive and dangerous style of play] when making decisions about starting or returning to a high-risk sport," says Dr. Moser.

"This study adds more information to our field, and intuitively many of us are concerned that ADHD may be a strong risk factor, but the lack of controls in the study make the results difficult to clearly interpret," she says.  "If both groups had been administered the KOSCHI questionnaire as a baseline, prior to injury, those findings could have accounted for the differences seen after concussion.  We just don't know.  Also, the psychometrics of the questionnaire are not as tight as those of other instruments, so there may be a lot of leeway in the administration/interpretation/reliability." 

1. Bonfield CM, Lam S, Lin Y, Greene S. The impact of attention deficit hyperactivity disorder on recovery from mild traumatic brain injury.  J Neurosurg: Pediatrics 2013. DOI:10.3171/2013/5.PEDS12424 (published online ahead of print, June 25, 2013)

2. Crouchman M, Rossiter L, Colaco L, Colaco T, et al. A practical outcome scale for paediatric head injury.  Arch Dis Child 2001;84:120-124.

Most recently reviewed December 4, 2015