Retired players who had the most depressive symptoms also had the most extensive damage to their white matter, which is the part of the brain that makes connections with the gray matter.
"These changes argue that depression is not just psychological because athletes are not playing their sport anymore," said study author Dr. Kyle Womack, an assistant professor of neurology and psychiatry at the University of Texas Southwestern Medical Center.
One white matter area in particular, which lies in the middle of the very front part of the brain, had structural changes in all of the athletes with depression, Womack said.
It would make sense that this area, which is involved in motivation and behavioral control and has been implicated in depression before, would be vulnerable to head collisions and trauma, he explained.
For her part, McKee said that identifying regions of the brain that are associated with depression could help doctors detect and treat early changes in athletes.
Blood and urine tests are also being developed to help determine immediately after an injury whether a player suffered a concussion, and make sure athletes only return to play after their brains have healed, McKee said.
The data in these two studies are considered preliminary until they have been published in a peer-reviewed medical journal.
To learn more about depression and treatments, visit the U.S. National Institute of Mental Health.
SOURCES: Nyaz Didehbani, Ph.D., L.P., research psychologist, Center for BrainHealth, University of Texas at Dallas; Ann McKee, M.D., co-director, Center for the Study of Traumatic Encephalopathy, Alzheimer's Disease Center, and professor, neurology and pathology, Boston University; Kyle W
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