(CNN) NFL running back Mike James calls it his medicine for pain management, but league officials call it a banned substance. Now, James' athletic career is hanging in limbo because he chose pot over pills.

In 2013, James was prescribed opioid painkillers after injuring his left ankle in a Monday night football game . Within weeks, he developed a dangerous dependency on the drugs.

To get off of the opioids, he turned to medical marijuana for his pain.

Suddenly, "my pain subsided," James told CNN Chief Medical Correspondent Dr. Sanjay Gupta in an exclusive interview in the documentary "Weed 4: Pot vs. Pills," which aired Sunday night.

"I never had something where I could be coherent and still have pain relief," he said.

Photos: History of marijuana in America Photos: History of marijuana in America Public perceptions about pot have come a long way, from the dire warnings of "Reefer Madness" to growing acceptance of medical marijuana and the legalization of recreational use. Hide Caption 1 of 41 Photos: History of marijuana in America Harry Anslinger was named commissioner of the Federal Bureau of Narcotics when it was established in 1930. While arguing for marijuana prohibition, he played on Americans' fear of crime and foreigners. He spun tales of people driven to insanity or murder after ingesting the drug and spoke of the 2 to 3 tons of grass being produced in Mexico. "This, the Mexicans make into cigarettes, which they sell at two for 25 cents, mostly to white high school students," Anslinger told Congress. Hide Caption 2 of 41 Photos: History of marijuana in America A poster advertises the 1936 scare film "Reefer Madness," which described marijuana as a "violent narcotic" that first renders "sudden, violent, uncontrollable laughter" on its users before "dangerous hallucinations" and then "acts of shocking violence ... ending often in incurable insanity." Hide Caption 3 of 41 Photos: History of marijuana in America Marijuana cigarettes are hidden in a book circa 1940. Congress passed the Marijuana Tax Act in 1937, effectively criminalizing the drug. Hide Caption 4 of 41 Photos: History of marijuana in America Even after Congress cracked down on marijuana in 1937, farmers were encouraged to grow the crop for rope, sails and parachutes during World War II. The "Hemp for Victory" film was released in 1942 by the U.S. Department of Agriculture. Hide Caption 5 of 41 Photos: History of marijuana in America A woman buys ready-rolled marijuana cigarettes from a dealer at her door circa 1955. Hide Caption 6 of 41 Photos: History of marijuana in America Members of the Grateful Dead talk with reporters from their home in San Francisco on October 5, 1967. The band was protesting being arrested for marijuana possession. Hide Caption 7 of 41 Photos: History of marijuana in America U.S. Customs agents track the nationwide marijuana market during Operation Intercept, an anti-drug measure announced by President Nixon in 1969. The initiative intended to keep Mexican marijuana from entering the United States. Hide Caption 8 of 41 Photos: History of marijuana in America Research scientist Dr. Reese T. Jones, right, adjusts the electrodes monitoring a volunteer's brain response to sound during an experiment in 1969 that used a controlled dosage of marijuana. The tests were conducted at the Langley Porter Institute at the University of California, San Francisco. Hide Caption 9 of 41 Photos: History of marijuana in America Marijuana use became more widespread in the 1960s, reflecting the rising counterculture movement. Hide Caption 10 of 41 Photos: History of marijuana in America People share a joint during a 1969 concert in Portland, Oregon. In 1973, Oregon became the first state to decriminalize cannabis. Hide Caption 11 of 41 Photos: History of marijuana in America Police dogs trained to smell out hidden marijuana examine U.S. soldiers' luggage at the airport during the Vietnam War in 1969. Drug use was widespread during the war. Hide Caption 12 of 41 Photos: History of marijuana in America Marijuana reform was the Life magazine cover story in October 1969. The banner read: "At least 12 million Americans have now tried it. Are penalties too severe? Should it be legalized?" Hide Caption 13 of 41 Photos: History of marijuana in America Protesters wade in the Reflecting Pool at the National Mall in Washington during the "Honor America Day Smoke-In" thrown by marijuana activists in response to the official "Honor America Day" rally organized by President Nixon supporters at the Lincoln Memorial on July 4, 1970. Hide Caption 14 of 41 Photos: History of marijuana in America Panel members of the National Commission on Marijuana and Drug Abuse attend a hearing In Denver on January 10, 1972. From left, Dr. J. Thomas Ungerleider, psychiatrist; Michael R. Sonnenreich, commission executive director; Raymond P. Shafer, commission chairman; Mitchell Ware, Chicago attorney; Charles O. Galvin, Dallas law school dean. The commission's findings favored ending marijuana prohibition and adopting other methods to discourage use, but the Nixon administration refused to implement its recommendations. Hide Caption 15 of 41 Photos: History of marijuana in America President Jimmy Carter, with his special assistant for health issues, Dr. Peter Bourne, beside him, talks to reporters at the White House about his drug abuse control message to Congress on August 2, 1977. Among other things, he called for the elimination of all federal criminal penalties for the possession of up to one ounce of marijuana. Hide Caption 16 of 41 Photos: History of marijuana in America First lady Nancy Reagan participates in a drug education class at Island Park Elementary School on Mercer Island, Washington, on February 14, 1984. She later recalled, "A little girl raised her hand and said, 'Mrs. Reagan, what do you do if somebody offers you drugs?' And I said, 'Well, you just say no.' And there it was born." She became known for her involvement in the "Just Say No" campaign. Hide Caption 17 of 41 Photos: History of marijuana in America Robert Randall smokes marijuana that was prescribed to treat his glaucoma in 1988. He became the first legal medical marijuana patient in modern America after winning a landmark case in 1976. Hide Caption 18 of 41 Photos: History of marijuana in America President George H. Bush holds up a copy of the National Drug Control Strategy during a meeting in the Oval Office on September 5, 1989. In a televised address to the nation, Bush asked Americans to join the war on drugs. Hide Caption 19 of 41 Photos: History of marijuana in America A television ad aired in 1996 by Republican presidential candidate Bob Dole's campaign included footage from a 1992 MTV interview of a laughing President Clinton saying he would inhale marijuana if given the chance to relive his college days. Hide Caption 20 of 41 Photos: History of marijuana in America Dennis Peron takes notes during a phone interview while Gary Johnson lights up at the Proposition 215 headquarters in San Francisco on October 11, 1996. The ballot measure was approved when voters went to the polls in November, allowing medical marijuana in California. Hide Caption 21 of 41 Photos: History of marijuana in America People in New York gather for a pro-cannabis rally on May 4, 2002. That same day, almost 200 similar events took place around the world to advocate for marijuana legalization. It was dubbed the "Million Marijuana March." Hide Caption 22 of 41 Photos: History of marijuana in America Different varieties of medical marijuana are seen at the Alternative Herbal Health Services cannabis dispensary in San Francisco on April 24, 2006. The Food and Drug Administration issued a controversial statement a week earlier rejecting the use of medical marijuana, declaring that there is no scientific evidence supporting use of the drug for medical treatment. Hide Caption 23 of 41 Photos: History of marijuana in America Medicinal marijuana patient Angel Raich wipes her eyes during a press conference on March 14, 2007, in Oakland, California. The 9th circuit U.S. Court of Appeals in San Francisco ruled that 41-year-old Raich, who used medicinal marijuana to curb pain from a brain tumor as well as other ailments, did not have the legal right to claim medical necessity to avoid the possibility of prosecution under federal drug laws. Hide Caption 24 of 41 Photos: History of marijuana in America Coffeeshop Blue Sky worker Jon Sarro, left, shows a customer different strains of medical marijuana on July 22, 2009, in Oakland, California. Voters in the city approved a measure during a vote-by-mail special election for a new tax on sales of medicinal marijuana at cannabis dispensaries. Hide Caption 25 of 41 Photos: History of marijuana in America A patient prepares to smoke at home in Portland, Maine, on October 22, 2009, a decade after the state approved a medical marijuana referendum. Hide Caption 26 of 41 Photos: History of marijuana in America Sonja Gibbins walks through her growing warehouse in Fort Collins, Colorado, on April 19, 2010. Since the state approved medical marijuana in 2000, Colorado has seen a boom in marijuana dispensaries, trade shows and related businesses. So far 20 states and the District of Columbia have made smoking marijuana for medical purposes legal. Hide Caption 27 of 41 Photos: History of marijuana in America Marijuana activist Steve DeAngelo wears a "Yes on Prop 19" button as he speaks during a news conference in Oakland, California, on October 12, 2010, to bring attention to the state measure to legalize marijuana for recreational purposes in California. Voters rejected the proposal. Hide Caption 28 of 41 Photos: History of marijuana in America Nutrient products are placed on shelves in the weGrow marijuana cultivation supply store during its grand opening on March 30, 2012, in Washington, D.C. The store is a one-stop-shop for supplies and training to grow plants indoors, except for the actual marijuana plants or seeds. Legislation was enacted in 2010 authorizing the establishment of regulated medical marijuana dispensaries in the nation's capital. Hide Caption 29 of 41 Photos: History of marijuana in America People light up near the Space Needle in Seattle after the law legalizing the recreational use of marijuana went into effect in Washington on December 6, 2012. Hide Caption 30 of 41 Photos: History of marijuana in America A man smokes a joint during the official opening night of Club 64, a marijuana social club in Denver, on New Year's Eve 2012. Voters in Colorado and Washington state passed referendums to legalize recreational marijuana on November 6, 2012. Hide Caption 31 of 41 Photos: History of marijuana in America Members of a crowd numbering tens of thousands smoke and listen to live music at the Denver 420 Rally on April 20, 2013. Annual festivals celebrating marijuana are held around the world on April 20, a counterculture holiday. Hide Caption 32 of 41 Photos: History of marijuana in America Sean Azzariti, an Iraq war veteran and marijuana activist, becomes the first person to legally purchase recreational marijuana in Colorado on January 1, 2014. Colorado was the first state in the nation to allow retail pot shops. "It's huge," Azzariti said. "It hasn't even sunk in how big this is yet." Hide Caption 33 of 41 Photos: History of marijuana in America In April 2014, Maryland became the 18th state to decriminalize marijuana possession. Research published by the Pew Research Center in February showed 54% of Americans support legalization of marijuana. Hide Caption 34 of 41 Photos: History of marijuana in America Matt Figi's 7-year-old daughter, Charlotte, was once severely ill. But a special strain of medical marijuana known as Charlotte's Web, which was named after the girl early in her treatment, has significantly reduced her seizures. In July 2014, Rep. Scott Perry, R-Pennsylvania, introduced a three-page bill that would amend the Controlled Substances Act -- the federal law that criminalizes marijuana -- to exempt plants like Charlotte's Web that have an extremely low percentage of THC, the chemical that makes users high. Hide Caption 35 of 41 Photos: History of marijuana in America In July 2014, the New York Times published " High Time: An Editorial Series on Marijuana Legalization ," which called for the federal government to repeal its ban on marijuana. Hide Caption 36 of 41 Photos: History of marijuana in America Alaska Cannabis Club CEO Charlo Greene prepares to roll a joint at the medical marijuana dispensary in Anchorage on February 20, 2015. Several days later, Alaska became the third state in the nation to allow recreational marijuana. Hide Caption 37 of 41 Photos: History of marijuana in America A woman smokes pot at her home in Washington on February 26, 2015, the first day it was legal to possess marijuana for recreational purposes in the nation's capital. Democratic Mayor Muriel Bowser defied threats from Congress by implementing a voter-approved initiative, making the city the only place east of the Mississippi River where people can legally grow and share marijuana in private. Hide Caption 38 of 41 Photos: History of marijuana in America Employees make last-minute preparations before the grand opening of the Cannabis Corner in North Bonneville, Washington, on March 7, 2015. The pot shop is the first city-owned recreational marijuana store in the country. Hide Caption 39 of 41 Photos: History of marijuana in America Georgia Rep. Allen Peake celebrates with Kristi Baggarly, holding her daughter Kimber, after the state Senate approved Peake's medical marijuana bill March 24, 2015 in Atlanta. The bill will legalize possession of cannabis oil for treatment of certain medical conditions, such as the seizures suffered by Baggarly's daughter Kendle. Hide Caption 40 of 41 Photos: History of marijuana in America An employee at Kaya Shack, a Portland, Oregon, medical marijuana dispensary, showcases three types of marijuana sold at the shop on June 26, 2015. Oregon legalized recreational marijuana use on July 1, 2015. Hide Caption 41 of 41

As it stands, the NFL and NFL Players Association prohibit active players from using marijuana as part of the league's policy on substance abuse

The only way around the policy is if a player has what's called a therapeutic use exemption indicating that the athlete requires the substance to treat a diagnosed medical problem

James made history last month as the first player to file for a therapeutic use exemption specifically for cannabis. On Thursday, he received a letter from the NFL, denying his exemption application. He vowed not to give up.

"My career is at great risk," said James, who is a free agent after being released by the Detroit Lions.

'I thought, "Weed? No, that's a street drug" '

Growing up, James vowed that he would never become dependent on drugs. He was raised by a single mother in Florida, and his father was in and out of prison for drug-related offenses, records show.

"Drugs tore up my family," James said. "So I wanted to just play football, go to school, stay in my books, not get into any trouble."

By his senior year in high school, James was one of the nation's top running backs, and he was offered a full athletic scholarship to the University of Miami

Playing football at the university was a dream for James, but by his sophomore year, he faced a nightmare. On the night of December 20, 2010, his mother died in a car accident

"My mom was a huge football fan," Mike James says of mom Elgusta, "and I got into football through her."

He turned to the sport that both he and his mother loved to help overcome his grief. "For him to be all right and mentally deal with this, he was going to lean on football," said his wife, Aubrey James.

Three years later, James was drafted by the Tampa Bay Buccaneers . As a Bleacher Report headline put it, James proved that he had the talent to enjoy a "promising future" with the Buccaneers, but then he injured his ankle, and his life changed.

Doctors prescribed a cocktail of opiates to deal with the pain, a common prescription among professional athletes for sports-related injuries.

A study published in the journal Drug and Alcohol Dependence in 2011 found that more than half -- 52% -- of former NFL players reported using opioids during their career, and 71% of those players reported misusing opioids.

The prevalence of current opioid use among those players was 7%, according to that study: about three times the rate of use among the general population. The study included 644 retired players who answered questions in a telephone survey about their opioid use.

James never worried about developing an opioid addiction, "because I was getting them from a doctor," he said, but Aubrey worried.

Within weeks of his injury, James joined the about 2.5 million Americans who struggle with opioid use disorder.

Mike James' wife, Aubrey, encouraged him to try medical marijuana for his pain instead of continuing to use opioids.

In an effort to help him stop using pills, his wife suggested that James use pot to treat his pain.

James, a 27-year-old father of two, knew that he needed to stop using opioids whenever he thought about "the notion that I would do what my father did to me, to my boys," he said. His sons are 4 and 1.

He remained skeptical, however, about using marijuana to make that change.

"I thought, 'Weed? No, that's a street drug.' I didn't even want to hear what it had to offer," he said, but after more convincing, he finally tried marijuana in February 2014, and it helped him get off the opioids.

"I felt like I was beginning a new life," he said.

Mike James says he stopped using opioids for his sons, 4-year-old Mike III and 1-year-old Niko.

Yet since cannabis is banned in the NFL and James was unsure how he could get more, he said, he didn't use it again until last year.

JUST WATCHED Goodell addresses NFL ban on marijuana use Replay More Videos ... MUST WATCH Goodell addresses NFL ban on marijuana use 00:48

Then, in August, James took a drug test as part of the NFL's routine testing program. In October, he learned that the test was positive for marijuana, leading to his filing of the therapeutic use exemption for cannabis.

"This is the first active player who's been willing to put their professional career on the line, to openly admit that they not only have been using this cannabis but need it to function at the highest level," said Dr. Sue Sisley, an Arizona-based physician who is a board member of the nonprofit Doctors for Cannabis Regulation and has been helping James with his exemption application.

"Mike's case is such a perfect example of why cannabis needs to be made available, because he's really not a candidate for opioids," she said. "So this is a safe alternative for him."

'I'm not ashamed of it. ... I have a life to live'

Twenty-nine states, the District of Columbia, Guam and Puerto Rico have approved some form of legalized cannabis . The first state in the US to legalize marijuana for medicinal use was California, in 1996.

As it turns out, 69% of Americans say they approve of a professional athlete using marijuana for pain, and 67% saythat using a doctor's prescription for an opioid is a greater health risk than using a doctor's prescription for marijuana, according to a Yahoo News/Marist Poll released last year.

The stance of the NFL remains somewhat unclear, and the league did not respond to a request for comment.

In 2016, the NFL Players Association formed a committee to investigate all pain management options for players, including cannabis.

"Our job is to find the best medical science to support your therapeutic use exemption," DeMaurice Smith, executive director of the NFL Players Association, told Gupta.

As for James' case, "what I would say to him and every NFL player: Our job is to figure out, how do we build the best medical support for the best treatment for you?" Smith said.

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James never would have guessed that he would make history due to a therapeutic use exemption, but if, 30 years from now, his biography states "medicinal marijuana advocate," he would be fine with that.

"I'm not ashamed of it," James said. "I'm not embarrassed about it. It is something that I will continue to use, because I have a life to live."