We continue to hear their names: former NFL linebacker Junior Seau, Steelers Hall of Fame center Mike Webster, Eagles safety Andre Waters, Hall of Fame quarterback and sports commentator Frank Gifford. Since their deaths, they have become high-profile examples of people diagnosed with chronic traumatic encephalopathy (CTE), a neurodegenerative condition for which there is no cure and can only be diagnosed by autopsy after a person dies.

Former Raiders running back Maurice Jones-Drew and 49ers linebacker Chris Borland may have voluntarily removed themselves from the game based, in part, on concerns that continuing to play football would increase their risk of developing CTE.

In the docudrama Concussion, Will Smith portrays Bennet Omalu, the doctor, among others, credited with bringing to light the evidence of CTE in the brains of former NFL players. In doing so, he also exposed a problem that needs further evaluation to determine its significance. Now out in theaters, the film has already added fuel to a national discussion.

As many experts will agree, however, the relationship between developing CTE and playing football remains unclear. The link between the number of concussions a person sustains and the risk of developing CTE is also uncertain. A person sustaining a sports-related concussion is different from a person developing a myocardial infarction, where our ability to objectively diagnose and treat the patient in a way that will improve outcomes, comes from experience and solid clinical research. We are still developing and learning the optimal evaluation and treatment for patients with sports-related concussions.

So we, as neuroscientists and sports medicine clinicians, want to examine the following: What is our best understanding of the science on sports-related concussions? And how do we separate the science from the hype?

Here is what we know:

  • Post-mortem pathologic analyses of brains of some NFL and college football players demonstrate evidence of pathology, including neuronal loss, tau deposition, and other findings, which are being called CTE.

  • Some living retired NFL players exhibit signs and symptoms of progressive neurodegenerative disease.

  • There is increased awareness about sports-related concussions.

Still, there are many important questions to be answered when it comes to determining long-term outcomes of sports-related concussions. Our own research studies, and others from labs across the country, are attempting to unravel these difficult questions about the short- and long-term effects of repeated brain trauma.

Here is what is unknown at this point:

  • Does a single concussion or repetitive concussions increase the risk of a person developing CTE?

  • Does a single concussion, overlapping concussions, or separate multiple concussions result in permanent brain damage similar to that observed in neurodegenerative diseases such as Alzheimer's, Parkinson's, and amyotrophic lateral sclerosis (Lou Gehrig's disease)?

  • Is there a threshold of the number of hits to the head or number of concussions reached before a child (or adult) may be at higher risk for developing CTE?

  • Do genetics predispose certain players toward developing permanent brain damage?

Although there are a few reports that attempt to link sport-related concussions and neurodegenerative diseases, what is lacking are controlled and rigorous prospective studies necessary to address these unanswered questions. This is important for us to establish for all athletes and people who sustain sports-related concussions.

Where does this leave us? How do we keep sports as safe as we can and yet not limit or curtail the benefits of organized competitive physical activity? Should we as a society restrict or outright ban contact or collision sports, particularly for young athletes?

We propose that we need more informed discussion on these critical decisions about sports. We need to be vigilant, since association is not causation. The benefits of participation in team sports are many and clear, and include providing lessons on values such as winning and losing, increasing parent-child interaction, and encouraging children to better interact with society. Furthermore, scientific evidence supports the importance of physical activity and exercise in improving brain health, particularly during the formative years.

As parents ourselves, as well as scientists and health-care providers, we are passionate about improving our understanding of sports-related concussions. While we wholeheartedly welcome the increased public awareness and societal discourse, what is further required is rigorous medical research that determines the effect of sports-related concussions on long-term outcomes. Only then can hype be separated from the science.

Ramesh Raghupathi is a professor in the Department of Neurobiology and Anatomy at Drexel University College of Medicine.  ramesh.raghupathi@drexelmed.edu
Eugene Hong, M.D., is the associate chief of the Division of Sports Medicine at Drexel University College of Medicine and chair of the Department of Family, Community, and Preventive Medicine. He is a team physician for Drexel, Philadelphia University, and the U.S. Lacrosse National Men's U19 team. eugene.hong@drexelmed.edu
Thomas Trojian, M.D., is a professor and chief of the Division of Sports Medicine at Drexel, as well as the lead physician for Drexel Athletics.  thomas.trojian@drexelmed.edu