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Can Contact Sports Cause A Degenerative Brain Condition? – Expert Q&A
Researchers are working to understand how often contact sports like rugby can lead to players developing Chronic Traumatic Encephalopathy (CTE).
The condition was called “punch drunk syndrome” nearly 100 years ago when scientists first noticed a link between repeated head knocks and cognitive, mood, & memory issues later in life.
Past research has suggested that we can say with high confidence that CTE is caused by repeated head knocks from contact sports, but that has recently been questioned by other scientists.
An additional concern is that the disease currently has no treatment and can only be diagnosed by examining the brain after death, leaving players in the dark and potentially affecting their mental health.
The Science Media Centre asked third-party experts about the evolving evidence around CTE.
Dr Paul Skirrow, Director of Neuropsychology Training, University of Otago, comments:
What does the research say about a link between sports head knocks and diseases like CTE?
“The brain is an extremely complex and vulnerable organ, and it’s just common sense that it needs to be handled with care. The scientific research is fairly clear that severe or repetitive head injuries are associated with poor long-term brain health.
“CTE has so far only really been found/studied in professional athletes in high-contact sports, particularly in sports like American Football, Boxing/MMA and, to a lesser degree, Ice Hockey and Rugby. These sports involve repetitive blows- often for hours, most days, over many years- and typically with a very high degree of rotational force. While no blows to the head are good for us, very few people will experience the same quantity of repeated blows to the head as a professional in the NFL or UFC – and the incidence of CTE is incredibly low in the general population.
“The brain is certainly sensitive to blows to the head but it is also sensitive to all kinds of other factors, including aging, illness and the general health of your body. Cardiovascular factors – blood pressure, alcohol use, smoking and poor diet – are also some of the biggest predictors of long-term brain health. There are many reasons why a person might have cognitive or mental health difficulties, so it’s wise not to jump to a conclusion that they have been caused by head injury.”
What does the current evidence mean for sporting codes like rugby in New Zealand?
“Certainly, all head injuries should be taken seriously. We’re lucky in New Zealand to have very comprehensive support for both concussion and more severe injuries through ACC (services for concussion are not widely available in many other countries). If you or a family member experience symptoms such as difficulties in concentration and memory, or a lasting headache after you have received a significant blow to the head, I’d encourage you to seek a referral to a local concussion clinic.
“Professional sporting organisations are much more aware of the impacts of head injury on their players and it’s now very common to see concussion protocols in place in most professional sports. Perhaps more of a concern is in amateur sports, where there are no pitch-side doctors or physios to tell the player they need to hit the dressing room.”
Conflict of interest statement: “I’m not aware of any existing conflicts of interest and I have no prior relationship with the authors of the studies by Nowinksi et al. (2022), Fortington et al. (2024), nor Grashow et al. (2024). I have previously acted as an unpaid consultant to NZ Rugby on their concussion assessment and management protocols.”
Dr Sarah Hellewell, Senior Research Fellow in Neurotrauma, Curtin University and the Perron Institute, Australia, comments:
What does the research say about a link between sports head knocks and diseases like CTE?
“Chronic traumatic encephalopathy (CTE) is a degenerative brain condition that can currently only be diagnosed when a person has passed away, by looking at particular markers within the brain tissue. There is now an established link between CTE and repetitive concussions, but this doesn’t mean that everyone who has experienced concussions will develop CTE. There’s a lot researchers still don’t know, including other risk factors that may make people more likely to develop CTE.”
What does the research say about a link between suicidality and CTE?
“Although a formal diagnosis of CTE can’t be made in living people, people who have gone on to be diagnosed with CTE after death often report changes in their memory, thinking and mood. Suicidality has been less studied. Some researchers have found no evidence of a link between CTE and suicidality, however a recent large study found that people who believed they were living with CTE had higher rates of suicidality. This may be related to a feeling that CTE is incurable, but more research is needed to understand this.”
How could concern about having CTE affect someone’s mental health?
“There is understandable concern about CTE among people with a history of repetitive concussions, particularly those who have played contact sports like rugby. This concern, coupled with the broad range of symptoms and a lack of diagnostic tools for living people, means that some people may be influenced by the ‘nocebo effect’ whereby a belief that they are living with CTE may make their symptoms more prominent and increase health-related anxiety. Researchers are just scratching the surface of how prominent this effect may be and what it may mean for the health of people who believe they have CTE.”
What does the current evidence mean for sporting codes like rugby in New Zealand?
“Sporting codes should do what they can to minimise the risk of concussions occurring, and ensure that players take adequate time away from training and matches to allow the brain to recover fully when a concussion does occur. The evidence on CTE does not necessarily mean we should stop playing sports like rugby, which has many other benefits outside health like keeping us connected to community. It’s important to remember that CTE is rare, and most people won’t develop it.”
No conflicts of interest.
Dr Benjamin Koh, Honorary Associate, Faculty of Business, Sports Management, University of Technology Sydney, Australia, comments:
What does the research say about a link between sports head knocks and diseases like CTE?
“Research has increasingly focused on the link between sports-related head injuries and neurodegenerative diseases like Chronic Traumatic Encephalopathy (CTE). While a strong association exists between repeated head trauma and CTE, causation remains unproven. Multiple factors, such as the type of exposure, individual susceptibility, and other health conditions, likely contribute.
“Medical studies indicate a link between repetitive head trauma and CTE in contact sports. However, not all athletes who experience head trauma develop CTE, suggesting other factors may play a role: e.g. number or type of head impacts; genetics; gender; and age at first exposure. Furthermore, how findings from sports like American football apply to others, like rugby, is unclear.”
What does the research say about a link between suicidality and CTE?
“Association between CTE and suicide is also inconclusive, with research hampered by selection bias. Depression, substance abuse, chronic pain, and life stressors—common among athletes— make it difficult to isolate CTE as a cause of suicide.”
How could concern about having CTE affect someone’s mental health?
“Misattributions about CTE, exacerbated by media portrayals, can worsen mental health issues, fuelling the nocebo effect where individuals believe they have CTE, even without a diagnosis.”
What does the current evidence mean for sporting codes like rugby in New Zealand?
“Litigation around CTE is increasingly common. However, proving causation is difficult since CTE develops over time and can be influenced by other factors.
“One could view the legal landscape as consisting of three periods:
- early phase: scientific knowledge of association is unknown; sport organisation may not have a duty of care to take any precautions since risk not foreseeable and is reasonable not to take precautions.
- middle phase (presently): strong association between concussion and CTE known but causation not factually established; proving sporting organisation’s negligence in preventing concussion was a necessary condition for CTE is difficult.
- third phase: scientific causation proven and widespread public knowledge; players who continue to play presumed to have voluntarily assumed risk.”
Conflict of interest statement: “I had previously examined and provided advice on the merits of a class action (on CTE in sports) to a plaintiff law firm in Australia.”
Science Media Centre NZ
Our aim is to promote accurate, evidence-based reporting on science and technology by helping the media work more closely with the scientific community.
The Science Media Centre is New Zealand's only trusted, independent source of information for the media on all issues related to science. Thousands of news stories providing context from and quoting New Zealand researchers have been published as a direct result of our work.
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