(CBS/WUSA)-- CTE is a degenerative brain disease that can affect athletes and veterans who are exposed to repeated trauma.

New research is shedding light on some of the first symptoms a patient might experience.

Lisa McHale donated her husband's brain to scientists studying the effects of trauma on the brain of athletes.McHale says, "In all the years that Tom was struggling, it never occurred to us in a million years it had anything to do with injuries he sustained playing football."

Afternine years in the NFL, Tom McHalebattled depression and abused pain killers. He died of a drug overdose at age forty-five. Researchers at Boston University School of Medicine studied his brain, and found he had chronic traumatic encephalopathy or CTE. The diseasedevelops in people with a history of repeated brain trauma. Now new study showsCTE may initially affect a person's behavior, mood, memory and thinking skills.

Dr. Robert Stern is thestudy author at BostonUniversity. He says, "There is this development of an abnormal protein in the brain that eventually gets worse and worse, destroying brain tissue, and those symptoms can result in full blown dementia.

The Boston scientists looked at the brains ofthirty-six male athletes diagnosed with CTE after their deaths.The researchers interviewed family members and reviewed the athletes' medical records.

Dr. Stern says, "One of the primary goals is to diagnose this disease during life. Hopefully, we can understand how common it is, how to treat it and how to prevent it."

Lisa says the changes in her husband Tom were gradual, starting with mood, then behavior, then memory.

Lisa remembers, "He was having real difficulty with depression and that seemed to be really shocking in Tom cause he was someone so full of life."

Lisa now works with researchers and other families to raise awareness of this debilitating disease. CTE is very similar to Alzheimer's; researchers hope their findings
will lead to new ways to help differentiate between the two diseases.

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