Concussions Explained
Researched and written by Jennifer Coates
What is a concussion?
The subject of concussions in sport has been making headline news for many years, especially since the infamous court case in America where athletes took the NFL to court over their handling of concussions in the sport and the rise in public awareness of CTE. But what exactly is a concussion? It’s a common misconception that a concussion is only serious when it causes someone to become unconscious, it is thought at least 90% of concussions do not involve the patient losing consciousness (Ellemberg,2009) or that they will at least display symptoms of concussion from the onset of the incident, when in fact its not as simple as that.
In the financial year of 2022/2023 over 679,000 people attended A&E departments within England with sports related concussions, there will be thousands more athletes that would of sustained a concussion that were never reported, my years of volunteering as an RFU accredited first aider for my local rugby team is evident of this, it was almost a weekly occurrence that I would suspect a player had a concussion which would lead me having to inform the player, coach and ref that they couldn’t play and then me having to then argue with the player that they needed to attend A&E to get checked, 99% of the time they would refuse so just my experience shows that the majority of concussions sustained in grassroots sports never end up in A&E and are never reported. In McKees study she reports that around 1.7 million people a year are diagnosed with a brain injury every year in the US, 75% of those were a concussion (mTBI) (McKee,2011).
A concussion, also known now as a mild traumatic brain injury (mTBI), mild brain injury (MBI), mild head injury (MHI) or a minor head trauma, is when the brain moves inside the skull caused by some sort of impact to the head or any sudden jerk that moves the body, neck or head. This movement of the brain within the skull causes the nerves and blood vessels in and around the brain to twist and stretch which in turn can cause the brain to stop working as it should. Its also a misconception that the skull or wearing a helmet protects our brains from a concussion, yes the skull does protect the brain by shielding the brain from direct impacts which would cause direct damage to our delicate brains but the brain ‘floats’ within our skull, with protective membranes and CSF (cerebrospinal fluid) encasing the brain within the skull, acting as ‘shock absorbers’ which cushions the brain against the skull, and helmets only protect our skulls from injury, which in turn can protect our brain if an injury to the skull was severe enough to fracture our skull but the helmet provides zero protection directly to our brain. Whenever our head, neck or body is involved in some sort of impact or acceleration and deacceleration movement this causes the brain to move with great force, the brain can violently move forwards, backwards or even twist within the skull with so much force that the brains natural shock absorbers are useless, the brain impacts the interior of our hard skulls. To make things worse, it might surprise you to learn that the inside of the skull is not smooth, in fact the interior of the human skull is made up of various bony structures, ridges and depressions which can all damage the surface of the brain upon impact. To understand what happens to the brain during a concussion imagine a jelly, the brain is much softer and delicate than people realise, most people presume its firm in nature when it’s actually very soft and squishy in texture, like butter or a set jelly, the images we see of a ‘firm’ brain are after a brain has been preserved after death for scientific purposes. Now imagine that jelly is in a container, if we were to shake the container the jelly stretches and deforms, but it also impacts the sides of the container which causes the jelly to continue to move, stretch and deform in the opposite direction when it impacts the container, even after we have stopped moving the container. This is what happens to our brain within the skull when we are involved in a collision, whether that is from a car crash, fall, contact sports or anything that has involved a rapid acceleration and/or rapid deacceleration. When we look at this analogy of what happens to the brain during a concussion it is not hard to see that the brain can become bruised, nerves and blood vessels becoming damaged and swelling of the brain tissue.
Symptoms of a concussion
There are a long list of possible symptoms that a concussion can cause, physical, cognitively and psychologically; Physical symptoms include headaches, neck pain, balance problems, dizziness, vertigo, nausea, vomiting, double vision (diplopia), blurred vision, sensitivity to light (photophobia) and/or sound (hyperacusis), ringing in the ears (tinnitus), temporary loss of consciousness, feeling of pressure in the head, fatigue, changes in taste and smell, drowsiness, dazed appearance, stumbling, clumsiness, disorientation, weakness in arms or legs, vision or eyes changing such as pupils bigger, smaller or even unequal sizes, lack of coordination, and disrupted sleep patterns.
Cognitive symptoms, confusion, short-term memory loss (amnesia), trouble concentrating, difficulty in finding things, difficulty reading, easily distracted, slurred speech, word finding problems and brain fog.
Psychological symptoms include depression, anxiety, mood swings, feelings of being overly emotional, personality changes, quick to anger, low motivation, feeling overwhelmed and irritability. Some symptoms can indeed appear directly after the concussion, it was previously thought that symptoms would appear up to 48 hours after a concussion but information from various studies are suggesting that for some patients symptoms can take 7-10 days to appear and in some rarer cases have taken weeks and months to appear, this is referred to as post-concussion syndrome(PCS). The problem we face with diagnosing a concussion is that unless the patient has experienced a severe concussion which causes immediate symptoms such as blurred vision, loss of consciousness or severe dizziness are obvious, it can be very hard to realise something isn’t right as the symptoms can be less obvious and can take hours, days or even weeks to present themselves. These ‘milder’ concussions do not mean that less trauma has been caused to the brain than someone who has been knocked out by their brain trauma, even if the patient continues to show no symptoms after the impact they can have sustained damage to their brain. This delay or even absence of symptoms after a concussion can cause some serious complications, especially for athletes of all levels. It is now widely accepted in the scientific community that an accumulation of ‘mild’ concussions and sub concussions cause irreparable damage to the brain, putting the athlete at risk of developing dementia and CTE, data from two studies in America demonstrate this. A survey of over 2000 retired professional American footballers, all of which had a history of countless sub concussive hits and concussions were more than 3 times more likely to have been diagnosed with depression (Guskiewicz,2007), another study discovered that professional American footballers who had died were 3 times more likely to have a neurodegenerative disease listed as their cause of death than the general population (Everett,2012). And then there is the catastrophic Second Impact Syndrome (SIS), this is an extremely dangerous event that happens when someone sustains a concussion after the brain has not recovered fully from a previous concussion, even a very minor impact or sub concussive impact can cause the brain to rapidly swell and/or herniate and can cause respiratory failure and even death.
Concussions in Children
The human brain continues to develop until our mid-twenties; it is common knowledge in the scientific community that any concussion to a brain that has not finished developing can cause permanent and sometimes serious life-long damage to their cognitive and behaviour functions. A recent study of over 448,000 children between the ages of 5 and 18 were studied and demonstrated alarming results with over 40% of the children who had suffered from a concussion were at an increased risk of developing mental health issues, psychiatric hospitalisation, and self-harming (Ledoux,2022). McKee states that the scientific community previously thought that a child’s brain was able to recover from a concussion due to it still developing and being “more plastic than a mature brain”, recent studies have shown that these beliefs were incorrect and that the undeveloped brain of a child or adolescent is actually more vulnerable and can result in prolonged cognitive and behavioural impairments, with the studies reporting “worse cognitive symptoms over one year after the concussion than adults” and that “the prefrontal cortex is one of the last brain structures to mature, it is not surprising that parents report attention deficits, hyperactivity or conduct disorder following a head injury to their child” (McKee,2011). Julius Möttönen reported in a recent study, “A mild, single concussion is often considered a relatively harmless event, but our research suggests that it can have long-term effects on learning and cognitive abilities, “research showed that around 15% of children that were studied were less likely to go onto further education such as university or college” (Möttönen,2025).
Recovery timescale for a concussion
So, what does science tell us about the recovery from a concussion? There are several different theories, with a multitude of studies looking into the answer to this question. There are however two things that all doctors, scientists and neurologists can agree on, the brains recovery time is not correlated with the source of the injury, the brain does not differentiate between a concussion being caused by a car crash or a fall, the brain will take the same amount of time to recover as say someone who sustains a concussion caused by sport. The other crucial point that scientists and doctors agree on is the person’s concussion history, "A greater number, severity, and duration of symptoms" with previous concussions can be predictive of longer recovery time (Harman,2013).
There was a recent study conducted in America where the brains of fifty people who had been diagnosed with a mild concussion against fifty people without one, the results were staggering. Although most symptoms such as headaches cleared up within a few weeks, their brain scans four months later after their concussion showed differences in the fluid movement on their brain, which would suggest their brains have not fully recovered from the concussion (Hallock,2023).
Dr Stamatakis from the Department of Clinical Neurosciences at the University of Cambridge stated on the University’s website “At present, we have no clear way of working out which of these patients will have a speedy recovery and which will take longer, and the combination of over-optimistic and imprecise prognoses means that some patients risk not receiving adequate care for their symptoms.” (Stamatakis,2023). Stamatakis was involved in a study conducted in conjunction with CENTER-TBI, the study looked at 108 patients who had sustained a concussion against 76 healthy volunteers, both sets of volunteers underwent brain scans and assessed for ongoing symptoms. The study showed that 45% of patients that continued to report and display symptoms had abnormalities within their thalamus part of their brains. This part of the brain would appear to be trying to compensate for the ongoing concussion symptoms by trying to communicate with other parts of the brain more than the volunteers who had no concussion. Woodrow said “Despite there being no obvious structural damage to the brain in routine scans, we saw clear evidence that the thalamus – the brain’s relay system – was hyperconnected. We might interpret this as the thalamus trying to over-compensate for any anticipated damage, and this appears to be at the root of some of the long-lasting symptoms that patients experience.” (Woodrow,2023). The study also showed that patients experiencing emotional symptoms such as depression had increased connectivity between the thalamus and the areas of the brain that where higher levels of serotonin are located.
The NHS websites advice on concussions and mild head injuries, state that you may continue to experience symptoms for up to 3 months with an estimated 80% of people will continue to display PCS symptoms for up to 3 months, but if you are over the age of 40 these symptoms can persist for 6-12 months. The NHS also advises that you should not drive, operate machinery and you should have complete (physical and mental) rest for 48 hours after the concussion happened. Their advice is “Getting enough rest in the weeks following your injury and resuming your normal activities gradually (not all in one go) will help you to recover faster.” Other general advice they provide; “Try to avoid stressful situations”, “Do not return to work until you have completely recovered”, “Do not play any contact sports for at least 3 weeks and without talking to your doctor first”, “You should avoid intense physical activities whilst you recover, returning to physical activity and sport too soon can: prolong the symptoms of concussion, increase risk of further concussion, increase risk of further injuries…” and that “Once symptoms have settled, and after a minimum of 14 days rest, you can begin to return to sport/exercise through a graduated return to play programme” (NHS, 2022). The obvious problem with the NHS guidance is the fact that recent scientific studies and data have shown that symptoms of a concussion can take much longer than the 14 days rest from sport ‘rule’, therefore you could return to sports not realising that your brain is still experiencing problems associated with the concussion.
References (in chronological order):
K.M. Guskiewicz, S.W. Marshall, J. Bailes, M. McCrea, H. P. Harding Jr, A. Matthews, J. Mihalik, R. C. Cantu. Recurrent concussion and risk of depression in retired professional football players. Med Sci Sports Exerc. 2007
D.Ellemberg, L.C. Henry, S.N. Macciocchi, K.M. Guskiewicz, S.P. Broglio. Advances in sport concussion assessment: from behavioural to brain imaging measures. J Neurotrauma. 2009
A. C McKee, D.H.Daneshvar, D. O Riley, C. J Nowinski, R. A Stern, R. C. Cantu. Long Term Consequences: Effects on Normal Development Profile after Concussion .Phys Med Rehabil Clin N Am. 2011
J.Everett. Lehman, M. J. Hein, S.L. Baron, and C.M. Gersic, Neurodegenerative causes of death among retired National Football League players. Neurology Journals.2012
A.Ledoux, R. J. Webster, A. E Clarke, D. B Fell, B. D. Knight, W. Gardner, P. Cloutier, C. Gray, M. Tuna, R. Zemek. Risk of Mental Health Problems in Children and Youths Following Concussion.JAMA.2022
NHS Emergency Department .Oxford University Hospitals Advice after a brain injury information for patients. 2022
K.G. Harmon, J.A. Drezner, M. Gammons, K.M. Guskiewicz, M. Halstead, S.A. Herring, J.S Kutcher, A. Pana, M. Putukian,W.O. Roberts. American Medical Society for Sports Medicine position statement: concussion in sport. Br J Sports Med. 2013
H. Hallock, M. Mantwill, P. Vajkoczy, B. Wolfarth, C. Reinsberger, A. Lampit, C. Finke. Sport-Related Concussion A Cognitive Perspective. Neurology journals.2023
E. Stamatakis. Almost half of people with concussion still show symptoms of brain injury six months later. https://www.cam.ac.uk/research/news/almost-half-of-people-with-concussion-still-show-symptoms-of-brain-injury-six-months-later. 2023
R.E. Woodrow, RE et al. Acute thalamic connectivity precedes chronic postconcussive symptoms in mild traumatic brain injury. Brain. 2023
J. Möttönen, I. Kuitunen, V. T. Ponkilainen, V. M. Mattila. Impact of childhood traumatic brain injury on educational attainment in Finland from 1998 to 2018: a retrospective register-based nationwide cohort study. European Journal of Epidemiology.2025
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