“The six-month stretch where I was both going through concussion-related symptoms and continuing to engage in football activities was the worst time of my life,” former Vanderbilt offensive lineman John “Jabo” Burrow told us by email of his time in college football.

That stretch came between spring practice in 2011, when he experienced what he considers to be an undiagnosed concussion, and the first game of that fall season, after which he chose to medically retire from a sport which is treated like a religion in the small city where he grew up.

“The acute symptoms were worse than anything I’ve felt since,” he says. “I was both suicidal and experiencing self-hatred … It was the first time I doubted my ability to trust myself with something as basic as how I was feeling … I would sit in my locker and dread my existence. I felt like I was just surviving practice by practice and at any point my brain was going to give out on me. The entire time, I had people questioning my commitment to the team.”

Vanderbilt did not reply to our request for comment for this article.

As we discuss in our forthcoming book The End of College Football: On the Human Cost of an All-American Game, head injuries are a defining feature of college football, just as it is an inextricable aspect of the tackle version of the sport at every level. A Boston University study has found that every 2.6 years of participation in football doubles the chances of contracting the degenerative brain disease chronic traumatic encephalopathy (CTE), symptoms of which include “memory loss, confusion, impaired judgment, impulse control problems, aggression, depression, suicidality, parkinsonism, and eventually progressive dementia.”

Participation in football also appears to increase the probability of developing Parkinson’s disease by 61% compared to athletes in other sports, a risk that is in turn 2.9 times higher for those who have played at college or pro level.

Compelling evidence suggests that the NCAA, the main governing body of college sports, has long understood the magnitude of the danger posed by the sport. In a 1973 letter, NCAA lawyer Donald Wilson wrote to the head of the body’s football rules committee that it should ignore warnings from medical experts of the dangers of head-first tackling because, “In my opinion, any heed paid to their suggestions will destroy present-day football as we know it … Kindly bear in mind that if any of their letters, speeches and/or reports are published in any periodicals, this will form the basis of devastating cross-examination of football coaches at all levels in the future.”

For its part, the NCAA says that its sports science institute “has taken a leadership role … in evaluating the impact of concussions and repetitive head impact, as well as developing groundbreaking research and best practices to mitigate the potential effects of head injuries in sport.”

Decades after Wilson’s comments, Burrow faced the consequences of brain trauma. He says that he has experienced 10-plus concussions in his life. Apart from one in a car crash, they were all a product of his football career, although he says only three or four were diagnosed. That aligns with the experiences of former players from the Power Five, the elite level of college football, who we spoke to for our book. One of them also explicitly remembers enduring at least 10 concussions during his career.

Burrow shared with us what it was like to experience those concussions. “It was very clear and never in doubt that I had something wrong with me. The common factor is I don’t have a clear memory of the moment of impact or the immediate aftermath of being helped up. All my memories start on the sideline being cared for by the training staff. So the first real symptom that comes to mind is the inability to recall what happened. Beyond that, the common symptoms for me were aversion to light, loss of appetite, inability to get to sleep or stay asleep, and migraine-like pain when bending over, getting up too quickly, or getting my heart rate up.”

One of the former players we spoke to for the book described his experience with concussions this way: “I could barely do school … I would forget what I was talking about mid-sentence. I’d be forgetting everything that happened like 10 minutes ago. I would just completely zone out sometimes. It was like I was halfway there. I couldn’t really control it.”

Another told us, “My helmet went flying, like 30 yards. And instantly, I started crying. I lost my breath. It wasn’t like I got the wind knocked out of me. It was like when you’re so scared that you can’t breathe … they sent me back out on the field. They did the concussion test, [found out] that I have a concussion. I sat out for maybe six practices, like a week and a half, maybe? Was right back out there like nothing happened.”

A third player explained it this way, “So like, ‘camp fog’ or ‘camp brain’ was something we’d discuss. And it was just so normal. I was never diagnosed with a concussion.” He believes there were a handful of times where he was concussed. “And my sophomore year, I was … throwing up on the sidelines. And [a linebackers coach] looked at me, and said, ‘You good?’ And he wasn’t asking, he was telling me. And he tousled my hair and kind of slapped my head jokingly, and he was like, ‘Yeah, you’ll be good.’ So unless you got knocked out, or the fans saw you stumbling off the field, you just played.”

For Burrow, in the weeks after he believes he was concussed, he said, symptoms persisted, including in the form of “depression-like symptoms”.

“Loss of interest in pretty much everything but staying hidden in my room, inability to focus on topics [and] tasks for longer than 15-30 minutes at a time, intense performance anxiety related to football practice,” he says. “If you’ve ever been hungover and have still had to function the next day, it’s very similar. Essentially, while I was playing, practicing, and going to school, it felt like I was hungover.”

It got to the point, he says, that “I remember sitting in my locker, fully dressed, completely dreading the idea of practice. I knew that the entire time would be spent just surviving.”

Part of the problem for Burrow was that he was a starter and thus facing high performance demands at practice: “It’s almost easier if you are a scout team guy, just because there is less expected of you in terms of performance day in and day out. I was burning thousands of calories each day, and had absolutely no appetite. It was very difficult for me to keep weight on at this time. I went from the high 290 [pounds] in the summer to the low 280s within a six-week span simply because I couldn’t force myself to eat. I was nauseous and hungover feeling.”

Burrow says he continues to experience the effects of the concussions he suffered: “The long-term effects are more related to brain development, in my opinion,” he says. “I have some things related to my ability to focus that are more commonly associated with traumatic brain injuries, but the biggest issues I have are surrounding executive functions. Organization and ability to concentrate on tasks are two of the more common day to day things that I struggle with more than I should for someone my age. The single biggest lasting issue that I tie directly to playing football is related to regulating my emotions. I’ve learned that the frontal lobe is vitally important in emotion regulation, and I can see a direct line between my brain injuries and the development of my frontal lobe. I have also been diagnosed with depression and anxiety, and my doctors believe there is a connection between my mental health and my brain injuries.”

Many of the players we spoke with for the book felt haunted by the specter of CTE, which can only be diagnosed after death through an autopsy, and other long-term consequences. One explained, “I feel like there’s a good chance that I will have CTE … But I won’t find out until I die, which isn’t comforting at all.”

Based on his experiences and understanding of the game, Burrow is not optimistic that the sport can ever genuinely be safe. “The game is fundamentally dangerous. I like to compare it to cigarettes. All they can do is slap a giant disclaimer on every sign-up form from little league on up saying, ‘You will negatively affect your brain development, the risks of traumatic brain injuries are ______’. The game is fundamentally flawed in that way, and it is simply dishonest to say otherwise.”

Given everything he told us, we asked Burrow if the sport – which he loves – should continue to exist.

“What a question,” he says. “It needs to be understood that where I am from [Warrior, Alabama], it is almost blasphemous to even ask that question … Having said that, my answer is still no. The game is inherently dangerous for your brain and the reality is that the sport has spent the last few decades purposefully pushing that fact under the rug. It pains me to say that.”

• Former players we spoke to for The End of College Football have been granted anonymity to protect them from reprisal and in accordance with academic research protocols and research ethics board requirements.