The average boxer with little or no boxing training will likely generate a punching speed of approximately 15 mph. However former welterweight champion and Mancunian legend Ricky 'The Hitman' Hatton could produce a punch with a velocity of 25 mph. Not all pro boxers will generate this kind of speed, let's say for arguments sake the average was 20 mph. Imagine being hit in the head with a padded bat traveling at 20 mph and you will begin to understand that damage accumulates quite quickly.
As you can imagine a boxer is at a high risk of traumatic brain injury especially concussion. Old school boxing trainers with little or no understanding of the physiological effects of brain trauma still encourage heavy sparring, as if that is the magic pill a fighter needs to ensure victory. The truthful, and for them painful, answer is it is not. The shame of it is though, they have their students brainwashed to the belief this is the only way.
I will concede it is the only way... to BRAIN damage!
The scariest thing I have seen recently are promoters who hold open sparring events to judge the level of talent to appear on their shows. Whilst this will help ensure fairer match ups, it again further subjects the athlete to additional brain trauma that they need not necessarily take. The other edge to this sword is the pressure applied to athletes to sell tickets, how does this have anything to do with concussion? As I have discussed concussion is a form of MTBI. This means that symptoms can be made worse by both physical and mental (cognitive) exertion. Thus adding this sales pressure increases the risk of prolonged mental health complications.
A film starring Will Smith discussed in some minor detail the impact of contact sports, the subject under review in the film was American Football. Though the film is new, Chronic Traumatic Encephalopthy (CTE) is not. Originally believed to affect boxers alone, this has expanded to encompass a wider demographic. CTE is a neurodegenerative disease which to date is still being researched. One of the larger problems with the current research into this degenerative disease is that it overlaps with many common neurodegenerative diseases.
That said sports such as boxing where the likelihood of suffering MTBI is increased, raises the risk of developing CTE since this is the only factor linking the two. Until more is known about this disease and its causes it could be deemed speculation that the two are connected. It will be interesting to see how the research into this progresses.
While the research continues I'd like to offer my own observation. One of the purported claims is a higher incidence of suicide of people who suffer with CTE. I personally know of no less than half a dozen suicides of friends and acquaintances from the boxing and Muay Thai circle. Whilst I cannot state whether they had CTE, it is almost certainty that they had a MTBI (concussion).