Baltimore Orioles slugger Chris Davis returns to the Rogers Centre Tuesday for the first time since he was slapped with a 25-game penalty for testing positive for a banned stimulant.

But because of Major League Baseball’s rules which allow players with a diagnosis of attention deficit hyperactivity disorder to apply for an exemption, Davis will be allowed to use the same drug — Adderall — for which he was suspended last September.

Last season, 112 MLB players were granted exceptions to take Adderall — about 10 per cent of the league. The adult prevalence of ADHD in the general population is 4 to 6 per cent, raising questions about the legitimacy of MLB’s approval process.

“It’s highly suspicious that they’re over-diagnosing it or (the players) are faking it so they can use these drugs,” said Dr. Doug Richards, a physician and professor of sports medicine at the University of Toronto.

According to baseball’s Joint Drug Agreement, players apply for a therapeutic exemption after they have been diagnosed by an “MLB-certified” clinician. From there, exemptions are granted by a three-person panel of psychiatrists with expertise in adult ADHD, who are jointly appointed by MLB and the players’ union.

The panel granted 112 exemptions for ADHD last season, down from 119 in 2013, but up from 103 in 2007. Eight players, including Davis, were suspended last season for using Adderall without an exemption. Only after a second positive test does a player receive a 25-game penalty, which is far less severe than the 80- and 162-game bans for steroids.

Davis was diagnosed with ADHD while a member of the Texas Rangers in the late 2000s, according to the Baltimore Sun, who reported last year that he was granted multiple exemptions to use Adderall but was for some reason denied prior to the 2012 season. He did not reapply in 2013 or 2014 and has not explained why, the paper reported. Baltimore manager Buck Showalter confirmed in December that Davis was granted an exemption for this season.

One oft-cited explanation for baseball’s higher rate of ADHD is that children with the disorder are drawn to sports as an outlet for their hyperactivity. But Richards, who has served as a physician for national teams and varsity sports subject to Olympic drug testing — and has managed therapeutic exemptions for ADHD medications — said the rates of ADHD among athletes in his care are “not even close” to those in MLB.

MLB commissioner Rob Manfred has previously said the league’s higher incidence of ADHD is not surprising.

“Our population doesn’t look like the nation,” he told USA Today back in 2012, when he was the league’s executive vice-president. “We are younger. We are higher income, and there’s no question attention is a key part of what these athletes do.”

Adderall, an amphetamine, is commonly prescribed to treat adults and children with ADHD, but it is banned in most athletic competitions for its performance-enhancing effects. The drug increases focus and attention, which is particularly desirable in baseball, a sport of intermittent bursts of exertion and concentration amid long stretches of inactivity.

The drug can also lead to heart problems, high blood pressure and anxiety if misused or taken without a prescription.

Baseball has long been linked to amphetamines, dating back to the 1950s and continuing through the ‘70s, ‘80s and ‘90s, when “greenies” were the drug of choice across the majors.

The late Tony Gwynn told the New York Times in 2003 that by his estimation half the league was on amphetamines during his career. “People might think there is a steroid problem in baseball,” he said then. “But it’s nowhere near the other problem; the other, it’s a rampant problem.”

But in the case of Adderall, at least, it’s also an effective medication for a disorder that, depending on whom you ask, is either over- or under-diagnosed. These are the competing forces MLB and other sporting bodies try to balance when granting exemptions to their drug policies.

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“Of course they aren’t all legitimate cases,” said Judith Wiener, a professor of applied psychology who studies children and adolescents with ADHD. “They aren’t all legitimate cases anywhere. So I’m sure some are not legitimate, but probably most are.”

Richards has doubts about the rigours of MLB’s exemption process. “For me it comes down to whether these players are being fully tested and submitting full evidence. If they are, holy smokes! Major League Baseball is a hotbed for ADHD,” he said. “I would have to see the evidence to believe it, though.”