By Dr. Mallika Marshall

BOSTON (CBS) – A new study from the Boston University School of Medicine raises more questions about the safety of youth tackle football.

Researchers focused on 211 football players who were diagnosed with chronic traumatic encephalopathy (CTE) after death and found that those who began tackle football before age 12 developed cognitive, behavioral and mood symptoms on average 13 years earlier than other players.

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CTE, believed to be caused by repetitive blows to the head, leads to profound degeneration of the brain.

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The researchers found for every one year younger that a player began tackle football, he developed symptoms of CTE a little more than two years earlier.

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Experts say since the study looked at deceased football players already diagnosed with CTE, it does not necessarily apply to the general population of youth football players, but they say, it makes sense that children, whose brains are rapidly developing, should not be sustaining multiple hits to the head.

Dr. Mallika Marshall