  More than 1 million students play high school American football annually, but
many health professionals have recently questioned its safety or called for its
ban. These concerns have been partially driven by reports of chronic traumatic
encephalopathy (CTE), increased risks of neurodegenerative disease, and
associations between concussion history and later-life cognitive impairment and
depression among retired professional football players.
  A recent observational study of a cohort of men who graduated from a
Wisconsin high school in 1957 found no statistically significant harmful
effects of playing high school football on a range of cognitive, psychological,
and socio-economic outcomes measured at ages 35, 54, 65, and 72. Unfortunately,
these findings may not generalize to younger populations, thanks to changes and
improvements in football helmet technology and training techniques. In
particular, these changes may have led to increased perceptions of safety but
ultimately more dangerous styles of play, characterized by the frequent
sub-concussive impacts thought to be associated with later-life neurological
decline.
  In this work, we replicate the methodology of that earlier matched
observational study using data from the National Longitudinal Study of
Adolescent to Adult Health (Add Health). These include adolescent and family
co-morbidities, academic experience, self-reported levels of general health and
physical activity, and the score on the Add Health Picture Vocabulary Test. Our
primary outcome is the CES-D score measured in 2008 when subjects were aged 24
-- 34 and settling into early adulthood. We also examine several secondary
outcomes related to physical and psychological health, including suicidality.
Our results can provide insight into the natural history of potential
football-related decline and dysfunction.
