Also known as “concussion,” chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disease believed to be the result of multiple mild traumatic brain injuries (mTBIs).
CTE was first described by Martland in 1928 as being “punch drunk,” a syndrome of confusion and ataxia in boxers having suffering repeated blows to the head.1 In 1937, Millspaugh described “dementia pugilistica,” symptoms of cognitive and motor dysfunction, once again mainly observed in boxers.2
The term “chronic traumatic encephalopathy” was first coined by Miller in 1966 to encompass the mood, cognitive, and motor dysfunctions of dementia pugilistica.3 In 1973, Corsellis introduced a pattern separating CTE from other neurodegenerative diseases.4
The modern definition of CTE was brought to the national spotlight by the case studies of Omalu et al. that highlighted neuropsychiatric and neuropathologic changes in National Football League (NFL) players,5 inspiring the movie “Concussion.” This article focuses on CTE in American football and why it is of importance to psychiatrists and mental health professionals.
Epidemiology and Risk Factors
The most common risk factor across case studies of CTE is a history of at least one mTBI. Onset generally occurs in mid-life, usually after retirement from professional play.6 Timing is variable, given the heterogeneity of career length among NFL players; many begin their careers in junior high school, but some start at the tender age of 6.7
Of 1.2 million interscholastic football players in any given year, up to 5.6% sustain an mTBI. The majority (53%) of cases, however, remain unreported to medical personnel.8
Although the literature supports a correlation between repeated mTBIs and CTE, definitive causation has not been determined.9 Still, 63% to 71% of players with repetitive mTBIs eventually develop CTE.10
Among NFL players, the reported prevalence of CTE ranges from 3.7%6 to 90%.10 This disparity is largely due to disagreement among clinicians regarding what constitutes an mTBI, and the consequences faced by NFL players, their coaches, equipment managers, and team clinicians reporting them.11
Players who are running-backs, begin play before age 12, and have a history of previous mTBI are at a high risk of re-injury.12 A relationship between number of years played, development of CTE, and the stage of phosphorylated Tau (pTau) pathology has also been suggested.10,12
Retired NFL players who have had 3 or more mTBIs have a 5-fold increased risk for mild cognitive impairment, and 3-fold higher risk for depression.13,14 The APOE ε4 genotype increases the risk for cognitive impairment in CTE.12