Concussions in the NFL lead to Depression



Professional football players who suffer from a concussion are more likely to develop long-term mental health episodes such as depression.


The prevalence of concussions in football has significant mental health ramifications. One concussion occurs every 2.44 NFL games. A study published in the American Journal of Sports Medicine looked at correlations between concussion incidences and depression (Nine-Year Risk of Depression Diagnosis Increases With Increasing Self-Reported Concussions in Retired Professional Football Players, 2012. Zachary Y. Kerr, et al.).

The study used a 2001 General Health Survey sent to the 3,729 members of the NFL Retired Players Association. A second General Health Survey was sent nine years later in 2010. The surveys asked questions regarding the respondents physical and mental health as well as the number of concussions suffered during their professional careers. Those exhibiting depression in the first survey were not used in the study.

Of the players who reported never having a concussion, only 3.0% were diagnosed with depression. Of those who reported suffering from 10 or more concussions, 26.8% were found to suffer from depression. The relationship between number of self-reported concussions and likelihood of suffering from depression was a linear relationship. Those who reported suffering from 3 or more concussions were twice as likely to suffer from depression as those reporting 1-2 concussions over their career and three times more likely than retired professional football players who did not suffer any concussions over their professional career.

Work on depression in US soldiers in Iraq has suggested there may be a link between tauopathies, tau protein deposits in the brain, and depression. Repeated head impacts elevate tau protein levels causing neural breakdown. The physical blow to the head could directly cause neuron death or breakage of neuron connections. Lesions in neural tissue could release harmful biochemical agents.

Concussions often go unreported, especially at the amateur level. This study highlights the importance of monitoring the accumulation of concussions. Other studies have found that concussions can lead to negative personality and cognitive changes. Although the dangers of concussions cannot be underscored enough, with regards to this study on concussions in former NFL players there are several limitations. Most significantly, it is likely that there are many lurking variables that this study could not account for. For example, risky behavior that leads to concussions may be favored in those prone to depression. Career-ending concussion accumulation may lead to depression. Nonetheless, the number of concussions suffered is a significant predictor of depression later in life.

Most likely, a positive relationship between concussions and depression would apply across sports, competition levels as well as to the military and other non-athletic instances.

Playing on Turf increases Injuries in the NFL


A recent study found that NFL games played on turf showed significantly higher rates of lower-leg injuries.



Across sports and competition levels, playing surfaces have been switching from natural grass to artificial turf. This has several health ramifications. Some researchers have speculated that the rubber polymers used in artificial turf cause cancer. Although turf’s carcinogenic properties have not been proven, a recent study of NFL players showed that the incidence of knee and ankle injuries is significantly higher in games played on turf.

The first NFL stadium to use an artificial playing surface was the Houston Astrodome in 1966. The surface, called AstroTurf, was manufactured by Monsanto and consisted of a padded-carpet over asphalt. In the 1990’s infill surfaces became popular and are widespread today. Infill surfaces consist of an interwoven mat of polyethylene fibers filled with rubber particles. The frequency of NFL games played on turf has been increasing over the years as more NFL stadiums adopt turf. The figure below demonstrates this trend over the previous decade.

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Several studies have looked at injury rates in football players based on field surface. A study done in the early 2000s found that ACL injury rates of high school players are higher in games played on turf. However, the same study found college players were more likely to sustain an injury on grass than turf. A recent study looked at several different lower leg injuries in NFL players using extensive data collected by the injury surveillance system maintained by NFL trainers (An Analysis of Specific Lower Extremity Injury Rates on Grass and FieldTurf Playing Surfaces in National Football League Games : 2000-2009 Seasons; 2012. Elliot B. Hershman, et al.). The study used data from NFL seasons from 2000 to 2009.

The aforementioned study looked at several different lower leg injuries in NFL players: knee sprains, MCL and ACL injuries, ankle sprains, inversions and eversions. Although all injury categories demonstrated a higher frequency in turf than grass, MCL (median collateral ligament) injuries and inversions (an ankle sprain where the ankle is twisted inwards) both did not show significance. The injuries that did show significantly higher prevalence on turf were knee sprains, ACL injuries, ankle sprains and eversions. The figure below shows the injury rates in NFL players based on a density ratio of turf over grass injury rates.

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ACL sprains occurred at a rate 67% higher on turf than grass. Eversion ankle sprains occurred at a rate 31% higher on turf than grass. Despite the significantly higher rates of injury on turf, this study was limited because it did not suggest any mechanisms by which turf causes higher lower-leg injury rates nor a means to make artificial surfaces safer.