More NFL players have tested positive this season for amphetamines, which include the ADHD drug Adderall.
The league doesn't identify the substance when a player is suspended for a failed test. But senior vice president Adolpho Birch acknowledged Wednesday an increase in the number of positives for that type of drug.
Since the start of last season, more than 10 players have publicly blamed their four-game suspensions on taking Adderall without a therapeutic use exemption. Players can apply for an exemption by submitting documentation proving they need a prescription to treat attention deficit hyperactivity disorder.
Birch speculates that more NFL players may be using stimulants because they've become popular among college students in general to aid studying.