Men who had experienced several episodes of concussion during a footballing career were more likely to suffer clinical depression later.
Previous research has suggested that head injury, of the type sustained during sports like football and boxing, might be linked to increased risk of Alzheimer's disease. Researchers at the Center for the Study of Retired Athletes worked with a group of over 2,000 ex-footballers to see if this was so.

Over half had experienced loss of consciousness - concussion - at least once in their career owing to a knock on the head. Just under a quarter had experienced three or more episodes of concussion while 12 per cent had had five or more such episodes. The researchers found no link between increased risk of Alzheimer's disease and concussion. But they did find an increased risk of clinical depression.

Eleven per cent of the retired players had been diagnosed with depression and 87 per cent of this group still suffered from it. Players with more than five episodes of concussion had a three fold risk of depression, and those with three to four episodes a two fold risk, all this compared to players who had not experienced concussion. The study suggests that people are at risk of depression for a long time after they sustain a mild brain injury.