The Senate inquiry into concussions and repeated head trauma in contact sports had its first public hearing this week, established in the wake of increasing concern about management of head injuries in sport and mounting scientific evidence showing links between head injuries and neurodegenerative disease chronic traumatic encephalopathy (CTE).

Neurologist Dr Rowena Mobbs has urged athletes and sporting bodies to take a conservative approach to concussion management, after being called upon to give evidence at the inquiry.

Mobbs is advocating for four weeks off play after a concussion diagnosis, "inclusive of that weekend's games, none of this sort of 11 or 12-day approach where you can scoot into that fortnight's games".

The NRL uses an 11-day stand-down period - though players are allowed to return sooner if they are cleared by an independent doctor - while the AFL utilises a 12-day timeframe before a player is allowed to return to play following a concussion.

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World Rugby's protocols state any player in line to return within 10 days of a concussion must be assessed by a World Rugby-approved independent consultant. The game's governing body has divided opinion as of late amid plans to lower the legal tackle height to reduce the risk of head injuries.

A four-week stand-down period would be a major game-changer in elite sport, with experts keen to diminish the risk of players suffering repeated head injuries in a short space of time.

Former NRL player Boyd Cordner was forced into retirement due to concussions, while promising cricketer Will Pucovski's career has stuttered in part due to a series of head knocks.

People who reported experiencing three or more lifetime concussions had worse cognitive function at baseline than those with no concussion history, according to findings published in the Journal of Neurotrauma.

UNSW Sydney has partnered with the University of Oxford and the University of Exeter to analyse more than 15,000 participants, marking the largest study to explore the cognitive effects of concussion to date.

Those who had reported three episodes of even a mild concussion had significantly worse concentration and ability to complete complex tasks. Those with four or more showed worse processing speed and working memory, with each additional concussion correlating with progressively worse cognitive deficits.

The study found just one moderate-to-severe concussion was associated with worse concentration, the ability to complete complex tasks and processing speed.

Sports Medicine Australia is reviewing its position on a 2019 paper which denied a clear causative link between head injury and CTE as a member of the peak sports medicine body's scientific advisory committee claims the link is "undeniable".

"In my view, the evidence for a causal relationship between repetitive head trauma and neurodegenerative diseases such as CTE is imperfect but it is undeniable at this stage," Dr Reidar Lystad said.

CTE is a degenerative brain disease characterised by the accumulation of an abnormally folded protein called "tau", which can only be detected at autopsy.

The disease can often manifest in life as behavioural changes, depression, anxiety, cognitive impairment and memory loss.

It has been found in the brains multiple Australian sportspeople, with the inquiry to examine the long-term effects of concussion and repeated head trauma from professional and community sport.

The Australian Sports Brain Bank, which has previously disclosed last year published its first extensive findings since inception in 2018, confirmed former AFL players Graham Farmer, Danny Frawley and Shane Tuck were found with various stages of CTE.

Twelve of 21 pledges were shown to have signs of CTE during autopsy. Five of the nine associated with the rugby codes were impacted by the disease, including Canterbury great Steve Folkes.

The Senate committee heard from the families of four athletes who were diagnosed with CTE, who described witnessing the decline of family members.

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