Up In Smoke? The Science Behind the NFL's New Pot Policy

Under the new drug policy, Josh Gordon may be released from suspension. Other players may not be so lucky. Credit: Leon Halip / Getty Images

On the heels of the suspension of several key NFL players for smoking marijuana, the League and the Players Association recently agreed to increase the maximum threshold of marijuana needed to test positive on a drug test. The new policy is meant to be a direct comeback to increasing criticism that the NFL's marijuana policies are harsh, outdated, and — as former Broncos tight end Nate Jackson told the New York Times — just plain "absurd." However, critics say if you look at the actual changes in the policy, they're largely symbolic.  

Players now have to show 35 nanograms per milliliter (ng/ml) of THC — the marker of marijuana — in a urine test rather than the stricter 15 ng/ml to test positive, appearing to allow for some leniency. But experts say the change is much less than it might seem. In fact, a 20 ng/ml difference has little meaning to the technicians doing the testing. "I think 15 is low for the standard, and increasing to 35 is just fooling around with the margins," says Dr. Daniel Lieberman, a psychiatrist at George Washington University.

20 ng/ml is small. The change is equivalent to dissolving a baby aspirin pill in one gallon of water, says Dr. David Casarett, a physician at the University of Pennsylvania. The World Anti-Doping Agency (WADA) on the other hand, which doesn't consider marijuana a performance enhancing drug, tests at 150 ng/ml (or more than seven baby aspirins in that gallon of water).


Furthermore, "the number itself is arbitrary because it depends when the urine test is given, relative to when the person smoked," explains Ziva Cooper, a psychiatrist at Columbia University. Many factors influence a positive test beyond a standard number, like how much weed a person smoked, how long ago they smoked it, if they smoke pot regularly (in which case their THC levels would remain high all the time), their body composition, and the chemical sensitivity of the test itself.

For example, if a player like LeGarrette Blount had one joint on the day he was arrested for possession, he would test positive at 15, 35, even 150. But Le'Veon Bell — who was arrested with Blount — might also fail his test at 15 or 35 if he had smoked as much as eight days prior.

For Lieberman, there's the fundamental question as to why the NFL is testing for marijuana at all — which, he notes, is not a performance-enhancing drug. If they really wanted to test for marijuana, Lieberman says, they should follow the World Anti-Doping Agency (WADA)'s more lax policy. This standard takes into account possible influences like secondhand smoke and the presence of non-marijuana drugs that might flag a positive. "I don't think 20 grams means much qualitatively, but it does say a lot in terms of what [the NFL]'s stance is," says Cooper. "The NFL is entering this dialogue when so much attention is on the therapeutic effects of medical marijuana," she says. 


It's turning out to be a difficult discussion. Lieberman says the league is also trying to maintain a clean-cut image. "If they dropped [the marijuana tests] completely, it would seem like they endorse marijuana use," he says. "The NFL is under a lot of pressure. Their players engage in bad behavior, and in some ways they're trying to maintain this image in the face of a lot of conflict they're facing in terms of publicity."