Evidence of the degenerative brain disease chronic traumatic encephalopathy has been found in a 25-year-old former football player after his death,  doctors say.

The degenerative brain disease, known also as CTE, is associated with repetitive head impacts, and can only be diagnosed by autopsy after death.

The unidentified 25-year-old played football for 16 years, beginning at the age of six, and had experienced 10 concussions, the first occurring when he was eight years old, according to letter  about the case written Boston University School of Medicine doctors.

During his freshman year, the young man, who played Division 3 college football, experienced a concussion with momentary loss of consciousness followed by headaches, neck pain and other symptoms that included difficulty with memory and concentration.

He stopped playing football in his junior year because of ongoing symptoms, began failing his classes and eventually left school before earning a degree.

The player, who had a family history of addiction and depression, later had difficulty maintaining a job and began using marijuana to help headaches and anxiety and to help him sleep. He died of cardiac arrest that was secondary to an infection in his heart.

This is the first autopsy-confirmed case of CTE in which neuropsychological testing was used to confirm the thinking difficulties associated with the condition, the authors say in their letter, which is appears in JAMA Neurology.