“The message here is that there’s less scientific understanding of what’s driving the symptoms in these younger players, and whether it’s related to brain trauma or perhaps other things,” said Gil Rabinovici, a professor of neurology and radiology at University of California, San Francisco, who is developing imaging techniques to diagnose dementia and C.T.E. in living patients. “It’s going to be important to look at other brain changes that are not tau related. We should be very cautious in trying to attribute their behavior to what we find in the brain.”

In the absence of a test that can determine if someone has C.T.E., athletes may, like Mr. Tamura, conclude that their cognitive problems are related to the disease. Dr. Rabinovici pointed to a survey of 4,180 former professional football players, 34.4 percent of whom believed they had C.T.E. based on symptoms that included headaches, cognitive difficulties, depression and thoughts of suicide.

Mr. Tamura took prescription medicine for anxiety, depression and bipolar disorder, his mother and police officials in New York said. He scribbled suicide notes showing his obsession with brain injuries. He believed his poor mental health was the product of playing football and repeated knocks to the head.

Dr. Rabinovici and other researchers have been working for years to develop a test for C.T.E. in the living. The most promising techniques include blood tests and brain imaging that can identify the tau protein in specific parts of the brain. The work on a solution is “slow and steady,” he said.

After years of public-relations crises and mounting evidence of a connection between football and C.T.E., the N.F.L.’s top health and safety official acknowledged a link in 2016. The league has steered children away from playing the sport in its regular form, encouraging safer tackling methods and promoting flag football.

Original source: us