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expert reaction to study looking at playing American football before age 12 and measures of mood, behaviour and cognition in later life

In a new cohort study, researchers publishing in Translational Psychiatry report that playing American football before the age of 12 may have long-term consequences for players’ moods and behaviours.


Prof. Seena Fazel, Professor of Forensic Psychiatry, University of Oxford, said:

“This study follows up 214 men who played American football at school, and uses a range of self-report measures administered online and by telephone to assess any longer term consequences to cognition and depressive symptoms.  When the researchers used information from all ages, changes in cognitive tests were no longer significant but there were some potentially important findings in relation to increased apathy and depressive symptoms.

“If validated in other research that uses more robust neuropsychological tests and diagnoses that rely on clinical assessment, it will add to increasing evidence that traumatic brain injuries in childhood and adolescence, even if apparently mild, need careful follow-up.  With clear pathways for treatment and management, any damaging effects on education, social functioning and cognitive health can be mitigated.”


Prof. Michael Swash, Emeritus Professor of Neurology, Barts and the London School of Medicine, said:

“This is a cross-sectional analysis of various behavioural and emotional features of a group of US American football players, that proposes that early exposure to the game is responsible for rather subtle abnormalities including depression and apathy (and perhaps cognitive defect – but this was not directly studied).  However, there are several limitations to this study which mean that this interpretation may not be sound.  This kind of research is very difficult to do.

“The paper hints in the introduction that repetitive concussive brain injury might have happened in these American football players, but does not provide any evidence for this suggestion.  Indeed, the nature of the sporting experience in these very young players – which must have included a wide range of type of player, level of game and exposure to concussion – is not clearly explained.  So we can’t tell from this paper exactly what the experience of the players was like, how many if any head injuries they had, or what risks were relevant, either in the games themselves or in training or in any other related sporting activity they may have undertaken.

“Secondly, no brain imaging or neurological examination was carried out in this study.  No formal neuropsychiatry, even in a subset of people, was set up.  So the way of measuring cognitive and emotional function was not very robust.

“Instead, the subjects were examined by various questionnaires many years later, and any suggestion of a cause and effect relationship is therefore tenuous at best – there are so many other features that could have been more important or could also have affected the types of cognitive or emotional features measured.  Lots of these confounding factors were not taken into account – for example, what was the social and educational background of these people?  Did they have a record of antisocial behaviour?  Was there a family history of social problems?  What was their educational level?  What medications had they been taking?  How accurate was any enquiry regarding substance abuse, or alcoholism?  Were they successful in their career aspirations and what was their income level?  Were medical records available?  If not why not?  Were sporting clubs’ records of the individual players made available – and if not why not?

“A leap of faith is required to accept any relationship other than an association without causality.  We just can’t know from this study whether playing American football is or is not responsible for any cognitive or emotional problems later in life.

“It’s also worth remembering that American football is not like football (soccer) at all – it is a stop and go game with massive bodily protection that if anything bears a relationship to rugby union.”


Prof. Huw Williams, Associate Professor of Clinical Neuropsychology, University of Exeter, said:

“This is an interesting study in that it suggests that American Football players, who started playing before 12 years of age, may have more likelihood of psychiatric problems in later life.  The brain does go through a number of growth spurts before and after 12.  Maybe there is some form of disruption due to the ‘hits’ (or sub-concussive blows) in American Football at these vulnerable times – but, of course, this is rather speculative.  Importantly, although the ‘early starters’ had more issues such as depressive symptoms, they were no worse on objective tests of their thinking and concentration.  So this doesn’t suggest an impairment of brain functions necessarily.  Such symptoms might be due to a host of other factors – which might be changeable over time.  It does, though, highlight a need for longitudinal follow up studies so we can better understand such injuries, especially during and beyond the time of brain development of childhood and young adulthood.  We need more research following people with these injuries to know whether they can affect a person’s school performance, or chances of getting a job, etc.

“Clearly in general there is a lot of concern over how any kind of brain trauma may affect development.  There are already published large scale, follow up studies, showing less good recovery in children and young people, compared to adults, about 20 years after Mild Traumatic Brain Injury1.  This is when there is indication of disruption of the brain functions (e.g. loss of memory for what happened), so this previous research had suggested that injury when the brain is maturating might be more problematic.”



Dr David Reynolds, Chief Scientific Officer at Alzheimer’s Research UK, said:

“As evidence of a link between high impact sports and problems with later-life brain function comes to light, it is important to identify the factors that might be behind to this association.  American football has perhaps received the most attention in terms of a long-term impact on brain health but there are still many questions about why some players might go on to experience neurological problems and others don’t.  The age at which people take up the sport is a potential risk factor, as people who start playing earlier may be exposed to collisions for longer and at a point in their lives at which the brain is still developing.

“This study found that taking up American football before the age of 12 was linked to an increased risk of mood and behaviour problems at age 51, but not to problems with memory and thinking skills.  The study did not look at whether people who started playing American football before the age of 12 had more physical damage to the brain or whether any group was more likely to develop dementia later in life.  While dementia can involve mood and behaviour changes as well as memory problems, there are a number of factors that can influence these aspects of brain function.  The researchers did take into account factors like depression and medication use, but teasing out cause and effect from studies like this remains a challenge.

“This study relied on telephone and online assessments which, though not unusual in research studies, are not as reliable as those that involve face-to-face monitoring by trained professionals.  Though the study involved a reasonably large group of participants, they were recruited from a small pool of willing volunteers that do not necessarily represent the whole population of former players.  People who think they may have problems with brain function are potentially more likely to volunteer for research and this could introduce a bias into research in this area.  As the study only involved male former American football players, we must be careful not to generalise the findings to other groups of people and or to other sports such as soccer or rugby.  However, the study does highlight the need for continued research into the risks of American football on brain health and the mechanisms underlying those risks.

“Sports like American football not only form part of many people’s social and cultural lives, but can contribute to a healthy active lifestyle.  It is important that findings highlighting the potential risks of any sport are followed up with further research so that people can make informed decisions about the activities they get involved in and how best to minimise any risks.”


Prof. Stuart Derbyshire, Associate Professor, Department of Psychology, National University of Singapore, said:

“Overall, I think this is a good study.  It has been performed to a technical high standard, the stats all look appropriate, and the authors acknowledge the more problematic aspects of the study.

“The biggest methodological problem, which, to their credit, the authors note, is that the sample was self-selecting.  That means they may have completed the study because they have already been told they have a problem and have already heard that it might be associated with playing football before age 12.  If that is the case, then the study could be amplifying the effects of a concern generated by previous reports.  People come forward because they have a problem, and the study duly demonstrates that their problem is real, but the study doesn’t and cannot demonstrate that their problem is associated with playing American football before age 12.  It only demonstrates that a concern about playing American football will motivate those who have problems to volunteer for studies examining the effects of playing American football.

“The stand out issue for me, which the authors do not comment on, is that the study reveals the lamentable general state of the American psyche.  In the sample that did not partake in American football prior to the age of 12, a whopping 40% (roughly) could be considered cognitively or emotionally impaired, according to this study.

“The total sample size was 214, with 101 playing American Football before age 12 and 113 after age 12.  Approximately 40% of the sample playing after age 12 were categorised as both cognitively and emotionally impaired.  Approximately 50% of those that did play before age 12 were categorised as cognitively impaired, and approximately 60% were categorised as emotionally impaired.  The size of these effects are significant – any given individual might tolerate a risk increasing from 4 in 10 to 6 in 10, but across a population an increased risk from 4 out of 10 to 6 out of 10 of having problems is significant and notable.  However, the fact remains that what is driving the effect is uncertain due to the study design (it’s a cross-sectional study), so we can’t tell from this what it is that is causing these effects.

“We also don’t know whether the increased impairment makes a meaningful negative difference to the person’s life.  Although the numbers with increased impairment are large, it is hard to know exactly what the numbers mean with regards to quality of life, job opportunities, education and so forth.  That matters because while being cognitively sharp and emotionally balanced are certainly good things, playing American football before age 12 might deliver other benefits that offset the losses.  Networking, social engagement, physical prowess, etc. might deliver opportunities that mean they outperform those who do not play American football until later.  Moreover, given the high general rates of apparent cognitive impairment this study reports in the later-playing population, it seems it is not the case that these measures of being cognitively or emotionally impaired in modern America is going to make you particularly unusual, so we might be suspect about the importance of these measures for general life.”


* ‘Age of first exposure to American football and long-term neuropsychiatric and cognitive outcomes’ by ML Alosco et al. published in Translational Psychiatry on Tuesday 19 September 2017.


Declared interests

Prof. Michael Swash: “None.”

Prof. Stuart Derbyshire: “I have no conflicts of interest excepting a long-standing support of the Pittsburgh Steelers.”

None others received.

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