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.