The death of former American football player Junior Seau has again highlighted the possibility of a link between concussions and severe depression.
Yesterday Seau, who played 20 years in the NFL,, was found dead in his San Deigo home.
An assistant professor of Neurosurgery at the University of Alabama in Birmingham, James Johnston Junior, says NFL players often experience post-concussion syndrome.
He says they have a higher rate of depression, substance abuse, and dementia, compared to the general population, and this is thought to be connected to head impacts.
A report by Centers for Disease Control and Prevention estimates that as many as 3.8 million athletes suffer a concussion each year in the United States.