Terry and Betsy Brennan gather around a laptop in the kitchen of their home in Irvine, Calif., alongside their daughter, Chanel Brennan Brewster, as they log in to a Zoom meeting. They’re about to find out whether their son and Chanel’s older brother, former Hawai‘i football superstar quarterback Colt Brennan, died with chronic traumatic encephalopathy, the degenerative brain disease brought on by blows to the head.

Chanel, who is a few months pregnant with her second daughter, says she’s naming her after Colt—Marley James. Bob Marley was Colt’s favorite artist, and James was Colt’s middle name. A framed jersey hangs on the wall beside them, commemorating Hawai‘i’s retirement of Colt’s No. 15.

Colt had been one of the best quarterbacks college football had ever seen. During his junior year at Hawai‘i, he set the NCAA single-season record for passing touchdowns with 58 and was projected to be an early pick in the NFL draft. He chose instead to return for his senior year in 2007, when he led the Rainbow Warriors to their first undefeated season and finished second in Heisman voting as Hawai‘i’s first finalist for the award. He finished his collegiate career with 31 NCAA passing records.

Injuries and surgeries derailed his NFL career, however, and a car accident on a Kona highway in 2010 left him with severe and permanent injuries that led to the end of his football career. He struggled with alcoholism and addiction for a decade after that, in and out of countless therapy and treatment programs, before finding Tree House Recovery in Costa Mesa, Calif., at the start of 2021. He thrived as the Tree House program integrated teachings on neuroscience and biology with writing alongside intense physical training and challenges. The Brennan family felt like they had the Colt they knew and loved back.

But in May 2021, Terry and Betsy returned home from a trip to Mexico and found Colt drunk and high in their home, having suffered a relapse. He was surrounded by bottles of vodka, cans of beer and canisters of nitrous oxide, one of his primary drugs of choice. Terry drove him to Hoag Hospital in Newport Beach, where he was told they were keeping Colt in the emergency room until he was able to enter detox. Instead, Hoag released Colt around 1 a.m. that night, whereupon Colt made his way to a nearby motel.

He apparently met some men who delivered various drugs to him.

At around 4 a.m., responding to a 911 call, paramedics found Colt unconscious and not breathing from an apparent drug overdose. Colt was taken back to the hospital, where he was in a coma and sustained by a ventilator and IV. When it became clear the damage done to his body and brain was irreversible, Colt was allowed to die. He was 37 years old.

Autopsy results eventually revealed Colt had died from the “combined toxic effects” of ethanol, methamphetamines, amphetamines and fentanyl. But the Brennans wanted to know more—they wanted to look deeper than the addiction, to what could have been happening in Colt’s brain to drive him into addiction, and what could be making it so hard for him to get and stay sober. The Brennans donated his brain to Boston University’s CTE Center to determine whether he had been suffering from the disease, which can only be diagnosed postmortem.

So now, on the other end of Thursday's Zoom call, Lisa McHale, director of legacy family relations at the Concussion Legacy Foundation, and Dr. Ann McKee, a professor of neurology and pathology at Boston and the CTE Center director, are ready to share what they found.

McKee said it was harder than usual for them to examine the brain due to the nature of Colt’s death. Since the drug overdose rendered Colt unconscious and unable to breathe for long enough that his entire brain looked as though it had suffered a gigantic stroke, he lost a lot of tissue that interfered somewhat with McKee’s examination.

She also identified significant traumatic brain injuries in multiple parts of his brain. The first she noted was a massive gap in the membrane that connects the two sides of the brain to each other. Colt suffered a significant cavum septum pellucidum that ran the length of the membrane, meaning there was a gap—or a cave—all along it that should not have been there. He also suffered a loss of tissue in his right frontal lobe that essentially left a hole there due to a substantial loss of tissue caused by the 2010 car accident.

While all of these factors made it more difficult for McKee to assess the extent of CTE in the brain, McKee was still able to confirm Colt’s brain showed CTE in the frontal cortex, the brain stem and other subcortical regions. “It was enough to call CTE Stage I,” she says. “But it might’ve been greater had we been able to really assess other regions.”

The traumatic brain injury (TBI) caused by the car accident alone would have been enough to create issues for Colt, and the Brennans did see a marked change in his personality after the incident. He became more emotional, and began drinking and using drugs more. Addiction by nature hijacks brains and damages them in a way that convinces the brain it needs the addictive substance to survive. This alone is often an enormous challenge to overcome.

Add in a TBI, particularly one to the frontal lobe, and that challenge becomes magnified. CTE on top of that creates a compounding effect. The prefrontal cortex governs executive function and decision-making, as well as the ability to process emotions in a healthy manner—and shut down his more destructive impulses.

“His ability to avoid those things was really diminished,” McKee says. “He’s got impulses that he can’t control. He’s got urges that are physical in nature. There’s a physical aspect to this. It’s not just will. And fortitude. And discipline. He’s got injuries that he’s trying to overcome.”