TUDIES IN BASIC NEUROSCIENCEhave demonstrated that mild traumatic brain injury (concussion) is followed by a complex cascade of ionic, metabolic, and physiological events that can adversely affect cerebral function for several days to weeks. 1,2 Concussive brain injuries trigger a pathophysiological sequence characterized earliest by an indiscriminate release of excitatory amino acids, massive ionic flux, and a brief period of hyperglycolysis, followed by persistent metabolic instability, mitochondrial dysfunction, diminished cerebral glucose metabolism, reduced cerebral blood flow, and altered neurotransmission. These events culminate in axonal injury and neuronal dysfunction. [2][3][4][5] Clinically, concussion eventuates in neurological deficits, cognitive impairment, and somatic symptoms. 6 Sport-related concussion is now widely recognized as a major public health concern in the United States and worldwide. 3,[7][8][9] Despite rule changes and advances in protective equipment, the incidence rate of concussion in contactAuthor Affiliations are listed at the end of this article.

A prospective cohort study was used to quantify risk factors for sports concussions. Analysis was based on a stratified cluster sample of North Carolina high school athletes followed during 1996-1999. Clustering was by school and sport, and the sample included 15,802 athletes with 1-8 seasons of follow-up per athlete. Concussion rates were estimated for 12 sports, and risk factors were quantified using generalized Poisson regression. Concussion rates ranged from 9.36 (95% confidence interval: 1.93, 16.80) per 100,000 athlete-exposures in cheerleading to 33.09 (95% confidence interval: 24.74, 41.44) per 100,000 athlete-exposures in football, where "athlete-exposure" is one athlete participating in one practice or game. The overall rate of concussion was 17.15 (95% confidence interval: 13.30, 21.00) per 100,000 athlete-exposures. Cheerleading was the only sport for which the practice rate was greater than the game rate. Almost two thirds of cheerleading concussions involved two-level pyramids. Concussion rates were elevated for athletes with a history of concussion, and they increased with the increasing level of body contact permitted in the sport. After adjustment for sport, body mass index, and year in school, history of concussion(s) remained a moderately strong risk factor for concussion (rate ratio = 2.28, 95% confidence interval: 1.24, 4.19). The fact that concussion history is an important predictor of concussion incidence, even in this young population, underscores the importance of primary prevention efforts, timely identification, and careful clinical management of these injuries.

Additional studies are needed to examine why female athletes are at greater risk for overuse injuries and identify the best practices for prevention and rehabilitation of overuse injuries.

Both the concussed athletes and those with orthopaedic injuries experienced similar state and trait anxiety and relied on similar sources of social support postinjury. However, athletes with orthopaedic injuries reported greater satisfaction with support from all sources compared with concussed athletes. In contrast, concussed athletes showed more significant predictor models of social support on state anxiety at return to play.