Traumatic brain injury multiplies the risk of major depression eightfold. While the emotional trauma of whatever caused such deep damage may be understandable, from a blast in a war zone to a blow on the playing field, there’s a physiological component, too, that neuroscientists have long suspected but have been unable to identify.

“As clinicians, a lot of us had a gut feeling that [TBI-associated depression] is a different disease,” said Shan Siddiqi, a Harvard Medical School assistant professor of psychiatry and a clinical neuropsychiatrist at Brigham and Women’s Hospital in Boston. “Why did nobody detect it before? I think the reason is because unlike other psychiatric disorders, TBI caused a sort of structural reorganization of the brain.”

https://www.statnews.com/2023/07/06/depression-after-traumatic-brain-injury/