Sportsmen "can turn violent after head injuries" AMERICAN footballers who suffer repeated concussion could develop a disease that affects their memory, mood and behaviour, according to a new study. The research shows chronic traumatic encephalopathy (CTE) - a brain disease associated with repeat brain trauma including concussions - has been found in amateur and professional athletes, members of the military and others who experienced repeated head injuries. Scientists examined the brains of 36 male athletes, ages 17 to 98, diagnosed with CTE after death, and who had no other brain disease, such as Alzheimer's. The majority had played amateur or professional American football, with the rest participating in hockey, wrestling or boxing. The participants" family members were interviewed about the athletes" lives and medical histories, specifically dementia, changes in thinking, memory, behaviour, mood, motor skills or ability to carry out daily living tasks. Their medical records were also examined. Study author Doctor Robert Stern, a professor of neurology and neurosurgery at Boston University School of Medicine in the United States, said: "This is the largest study to date of the clinical presentation and course of CTE in autopsy-confirmed cases of the disease. However, the overall number of cases in the study is still small and there may be more variations in CTE than described here. The researchers found that 22 of the athletes had behaviour and mood problems as their first symptoms of CTE, while 11 had memory and thinking problems as their first symptoms. Three of the athletes did not show any symptoms of CTE at the time of death. Those with behaviour and mood problems experienced symptoms at a younger age, with the first symptom appearing at an average age of 35, compared to an average age of 59 for those with memory and thinking problems. The group that experienced mood symptoms was more explosive, out of control, physically and verbally violent, and depressed than the group that experienced memory and thinking deficits, with family members reporting that 73 per cent of those in the first group were "explosive," compared to 27 per cent in the second group. Nearly two-thirds (64 per cent) of the first group were described as being "out of control," compared with 27 per cent of the second group, and 68 per cent were physically violent, compared with 18 per cent. Earlier this month, Glasgow-based neurologist Dr Willie Stewart established a link between playing rugby and early- onset dementia. Dr Stewart said he had examined sections of brain tissue in a retired rugby player and found abnormal proteins associated with head injuries and dementia. The unnamed former player who took part in the study was found to have higher levels of the protein than a retired amateur boxer who has dementia pugilistica - more commonly known as punch drunk syndrome - which is thought to affect up to 20 per cent of boxers who retire after long careers.