The recent death of former NFL linebacker Junior Seau has raised fresh concerns about NFL guidelines pertaining to the treatment of concussions, medically known as mild traumatic brain injuries, and related health effects. In fact, Seau's family has even donated his brain to medical researchers in the hopes of furthering the understanding of the long-term effects of repeated concussions.

In addition to Seau's shocking suicide, the NFL is also contending with the news that some 100 additional players, on top of the more than 1,500 who have already stepped forward, are filing a class-action lawsuit against the league. The former players contend that the league "repeatedly refuted the connection between concussions and brain injury," according to a report by The list of players filing claims against the NFL includes former Probowlers.

Although these headlines might come as a shock to many fans, neurologists and neurosurgeons, particularly those accustomed to dealing with athletes, aren't quite so surprised. As James Johnston Jr., M.D., assistant professor of neurosurgery at the University of Alabama, Birmingham, puts it in a release appearing on Science Daily:

"NFL players often experience post-concussion syndrome. They have a higher rate of depression, substance abuse, and dementia compared to the general population — it's thought this is connected to head impacts."

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Numerous studies have linked concussions to weakened brain functioning. A study published in 2009 in the Journal of Neurotrauma found that while concussed athletes might perform normally in standard tests administered by medical practitioners to anyone suffering such an injury, they may still show suppressed brain functioning.

Although the common perception is that a concussion might be caused by one especially bad hit, a two-year study of high school athletes by Purdue University researchers found that mild traumatic brain injuries were in fact caused by a series of hits rather than a single blow to the head. In fact, even players never diagnosed with concussions still displayed changes in their brains as a result of the toll of the season.

Multiply that season after season over the career of an NFL veteran, and another picture emerges of the long-term consequences of year after year of hard impacts. In fact, as a result of the damage their bodies endure over their careers, NFL players are significantly more likely to abuse prescription painkillers than the rest of the population, according to a study published in the journal Drug and Alcohol Dependence.

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When it comes to determining a cause for what drove Seau to the depression that led him to take his own life, chronic traumatic encephalopathy is certainly one of the more likely culprits. This condition had already been linked to other former NFL players, including Tom McHale, Andre Waters, Mike Webster, Terry Long and many others. All displayed symptoms ranging from depression to dementia to memory loss and more — all of which are signs of CTE. CTE, however, can only be diagnosed postmortem following an examination of the brain.

What caused Seau's death still needs to be determined. For its part, the NFL is more sensitive to concussions and brain injury recently than it has been in previous generations. According to research published in Sports Health in 2010, players who suffered concussions are now sidelined longer rather than being put immediately back into play as soon as symptoms subside.

According to the Centers for Disease Control and Prevention, around 3.8 million Americans, ranging from those competing in professional leagues to children playing youth sports, suffer sports- or recreation-related concussions every year.

Photo: Junior Seau, considered one of the best players in NFL history never to claim a Super Bowl ring, appears in uniform for the San Diego Chargers early in his career, which spanned 16 seasons. Credit: Corbis Images.