Research has shown that athletes in American football, rugby and combat sports have a significantly higher risk of developing CTE than the general population.

CTE can only be diagnosed after death. The disease, which is caused by repeated blows to the head, has been found in the brains of hundreds of former NFL players.

The Boston University CTE Center said, external in 2023 that it had diagnosed CTE in 345 of the 376 former NFL players it had studied.

The NFL has agreed a $1bn (£700m) settlement after being sued by a group of more than 5,000 former players. More than 21,000 ex-players could be eligible for compensation.

In the first stage of the disease, some people also experience short-term memory problems, depression, aggressive tendencies, and executive function issues, according to the CTE Society, a non-profit group.

In later stages, those problems grow stronger and others, such as mood swings and suicidal thoughts, can emerge.

In its final stage, a person can experience severe cognition issues and memory loss, as well as dementia, according to the CTE Society.

Boston University’s CTE Center said the cause of suicide was complex and a CTE diagnosis was not known to be a risk factor for suicide.

But CTE researchers said the case showed not enough had been done to lower the risk of the disease for athletes.

“Mr Kneeland played in the modern era of concussion protocols and better helmets, and yet he still developed CTE,” said Dr Chris Nowinski, co-founder and CEO of the Concussion & CTE Foundation.

“We have no reason to believe the current generation is at a lower risk of CTE than previous generations.”