A recent tragic shooting in Midtown Manhattan has pulled an obscure but alarming brain disease back into the headlines. The shooter reportedly left behind a suicide note claiming he suffered from CTE, short for chronic traumatic encephalopathy, a condition linked to repeated head trauma. As shocking as the incident was, it has opened up a floodgate of questions: What exactly is CTE? Can it really make someone act out violently? And how can we even know if someone had it?What Exactly Is CTE?CTE is not your everyday concussion aftermath. It is a progressive, degenerative brain disease caused by repeated head injuries, the kind you get from rough contact sports, military service, or just too many unfortunate falls. Over time, these impacts seem to trigger the buildup of an abnormal protein in the brain called tau. This sticky substance does not just sit there quietly. It gradually spreads through the brain, messing with vital functions and causing serious, irreversible damage.The Symptoms People with CTE do not wake up one morning knowing something is wrong. The symptoms can creep in slowly, subtle at first, then increasingly hard to ignore, leading to memory lapses, confusion, impulsive behaviour, unexplained aggression, mood swings, deepening depression and, in many tragic cases, suicidal thoughts.It is the sort of change that can feel like a personality transplant. Loved ones often report seeing someone “become a different person” over time.Not Just a Pro Athlete ProblemFor a long time, CTE seemed to be the unwanted souvenir of retired American football players. The sport's culture of full-body collisions made it the perfect storm for head trauma. But recent research is telling a more disturbing story. A 2023 study uncovered CTE in younger, amateur athletes, including teens as young as 17.Back to the Manhattan case. While the shooter’s note mentioned CTE, we still do not know whether he actually had it, let alone whether it influenced his behaviour. This brings up messy territory: should possible brain disease be considered in criminal responsibility? Can CTE be a mitigating factor in violent crime?It is a grey zone. And until we develop reliable tools to diagnose CTE in the living, we are mostly left guessing.What Can We Do?CTE is a slow, silent thief, robbing people of their memory, emotions, and identity. And while scientists are racing to understand it better, prevention remains our best bet for now. That means:Rethinking how we approach youth and professional sportsReducing repeated head trauma wherever possibleKeeping an eye out for changes in behaviour following head injuriesCTE is not some mysterious ailment that only haunts linebackers. It is a very real, very scary consequence of repeated trauma to the brain, and as we are learning, it can touch more lives than we ever thought. It is time we start treating our heads with the same care we give the rest of our bodies, maybe even more.