Student athlete concussions and postconcussion syndrome

Concussion affects an estimated 1.1 million persons in the United States annually and 1 person in 3 during their lifetime.^1,2 Approximately 20% of head injuries are related to sports or physical activities.³ Concussion, known medically as mild traumatic brain injury, is a topic of considerable public interest, given the growing awareness about chronic traumatic encephalopathy among professional athletes. Student athletes have an increased risk of concussions compared with nonathlete students, which raises concerns about consequences.

In this issue of Neurology® Clinical Practice, Iaccarino et al.⁴ evaluated attention-deficit hyperactivity disorder (ADHD) among student athletes. They measured functions with standardized scales such as the Behavior Rating Inventory of Executive Function, British Columbia Postconcussion Symptom Inventory, and Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT). They reported that student athletes with ADHD are more likely to sustain 1 or multiple concussions and experience prolonged postconcussion symptoms. Students with ADHD may be 5 times more likely to sustain a sports-related concussion. They acknowledge that their study is complex and that simple scales do not always fit these complex clinical situations. Their findings are similar to those reported by Liou et al.⁵

Inattentiveness and impulsiveness are likely risk factors contributing to sports-related concussions. This is a reasonably believable observation: that inattentive or impulsive students with ADHD find themselves in harm's way far more often than other student athletes—with an alarmingly high rate of injury.

Postconcussion symptom recovery duration is harder to assess. Concussion symptoms can be difficult to separate from ADHD baseline symptoms. No intrasubject baseline was used for comparison in this study. Many postconcussion symptoms present as a clinical picture similar to ADHD itself.⁶ The standardized scales can be hard to use in these settings. For example, the ImPACT scale itself is open to discussion about its subjectivity. A player can bias the test by deliberately scoring low in preseason baseline testing. One wonders how ImPACT scores among ADHD persons differ from those of the general population irrespective of a concussion. The ImPACT concussion scale has known inaccuracies among ADHD students,⁷ and its validity is open to debate.⁸ Mood disorder, migraine, and other confounders also cloud assessment of a concussion recovery picture. International guidelines suggest that the likely duration of symptoms after a sports-related concussion is less than a month.⁹ A prolonged recovery duration among ADHD students remains unclear.

Subthreshold ADHD refers to patients with too few ADHD symptoms to make a formal ADHD diagnosis, usually persons having only 4 or 5 of the 9 ADHD inattention criteria required for diagnosis by the Diagnostic and Statistical Manual of Mental Disorders (DSM–5). This term is less familiar to most neurologists. Iaccarino et al. included subthreshold ADHD subjects in their study and go on to say, “subjects with subthreshold ADHD have a similar level of morbidity and dysfunction as those with the full ADHD.” They have only a modest number of subthreshold subjects—too few to draw conclusions with confidence based on these data alone.

A problem arises if subthreshold ADHD is the basis for treating student athletes with stimulant medications. Those medications improve performance for both ADHD and non-ADHD persons, leading the World Anti-Doping Agency¹⁰ to ban those substances during competitions unless the athlete presents a physician's note attesting to a diagnosis of ADHD. There is no exemption for subthreshold ADHD. Many symptoms for subthreshold ADHD might provide a back door for athletes to claim a basis for using performance-enhancing drugs, an undesirable situation.

Overall, this remains an interesting area of convergence of several topics of current interest, each ripe for further research: sports-related concussion, chronic traumatic encephalopathy, ADHD, and use of performance-enhancing medication in sports. Issues in the Iaccarino et al. report needing more study include subthreshold ADHD in sport-related concussion and the duration of sport-related postconcussion symptom among patients with ADHD.

The study by Iaccarino et al.⁴ is relevant for the practicing physician in emphasizing the increased risk of concussion among student athletes who have ADHD. The likelihood of a concussion may be five times that of student athletes without ADHD or subthreshold ADHD, and those with ADHD are more predisposed to multiple concussions. Coaches, trainers, team physicians, physical education teachers, prescribers of ADHD medications, and parents of youth athletes should be made aware of this. Students with ADHD, and their parents in the case of youth athletes, should be counseled about the increased likelihood of concussion in sports. Risks of return to play should be discussed clearly when any residual symptoms remain, with physician advice to avoid return to play when significant symptoms remain.

Author contributions

M.R. Nuwer: drafting/revising the manuscript. J.M. Nuwer: drafting/revising the manuscript. J.W. Tsao: drafting/revising the manuscript.

Study funding

No targeted funding reported.

Disclosure

M.R. Nuwer has received travel reimbursement from the American Clinical Neurophysiology Society; serves on the editorial boards of Neurology Clinical Practice and the Journal of Clinical Neurophysiology; is an honorary consulting editor for Clinical Neurophysiology; receives research grant support as investigator of studies for the Congressionally Directed Medical Research Programs (SC130209), the NIH/National Institute of Neurological Disorders and Stroke (1R01NS078494-01A1), and the United States Army Medical Research Acquisition Activity (11501944); has received personal compensation for book royalties from Cambridge University Press; holds stock/stock options in CortiCare; and has provided expert medical testimony for trials and depositions as a medical expert and treating physician. J.M. Nuwer has provided expert medical testimony for depositions as a medical expert. J.W. Tsao serves on the editorial board of Neurology: Clinical Practice; receives publishing royalties from Springer; and owns stock in Biogen and Illumina. Full disclosure form information provided by the authors is available with the full text of this article at Neurology.org/cp.