Denver is at the forefront of America’s next drug reform movement — again.

Thousands of residents have signed on in an effort to loosen restrictions on psilocybin mushrooms. In three months, a question about decriminalizing the psychedelic drug will appear on the city’s elections ballots alongside the mayoral election and more mundane affairs.

The campaigners behind the Decriminalize Denver measure already have made history: This is the first time U.S. voters will consider giving a second chance to the drug, which was the subject of great scientific interest before its reputation was annihilated in the 1970s.

Now, the measure has raised the same fear and excitement as the marijuana liberalization effort: Will it cement the city’s reputation as a mecca for drugs, effective progressive policies, or both?

“People from all over the world are getting in touch with us,” said Kevin Matthews, the 33-year-old, stay-at-home dad who is managing the campaign. “That’s what’s exciting about this: The fact that this is getting international attention, very positive attention, I think speaks to the movement overall.”

Here’s what you need to know about the drug, its legal history and the question on Denver’s ballot.

The ballot measure

Even if voters approve the new law, it would remain illegal to buy, sell and possess the drug.

Instead, the measure would attempt to tie the city’s hands on enforcement. It would instruct police officers that adult psilocybin users should be their absolute lowest priority — the last thing they should do. See a person jaywalking and a person with a sack of shrooms? Get the jaywalker.

“I do believe that is the first ‘lowest law enforcement priority’ initiative for psilocybin,” said Art Way, state director for the Drug Policy Alliance. “In that aspect, it is groundbreaking.”

Arrests related to psychedelics are relatively rare, but the penalties are far more serious than for typical marijuana charges. Possession alone is a felony punishable by up to a year in prison and a hefty fine. Most defendants escape jail time, but it’s always a threat, according to attorney Rob Corry.

Since 2016, the Denver Police Department has counted about 158 psilocybin-related arrests. The proposed change applies only to people over 21.

What mushrooms do

Matthews’ psilocybin journey to the psychedelic reform movement started somewhere unusual: the U.S. Military Academy at West Point.

“I had worked, up until that time, basically my entire life, to not only get into West Point but also to be a career military officer in the U.S. Army,” he explained in a Denver Post interview. But he left the academy after three years because of major depression.

“I didn’t graduate, I didn’t receive a commission — and honestly, that destroyed me,” he said.

Today, he said, he is using the leadership abilities he learned “in a totally different way” on the political campaign. He is one of many who say that psilocybin changed their perspective.

Psilocybin is a psychedelic drug that can send users into a mental trip for three to six hours. Its effects are variable, but users might feel as if time itself is slowing while their senses meld together and they’re confronted by hallucinations and spiritual experiences, according to the Center for Substance Abuse Research.

New research from Johns Hopkins University has shown that those experiences can help people make permanent life changes — at least when used in a controlled, therapeutic setting. Researchers also have found that the drug can bring on terrifying and disturbing experiences, though.

“It allowed me to see outside the box that depression had created. It opened me up to a new world of possibility,” Matthews said.

But the decriminalization campaign won’t focus on the drug’s potential benefits, he said. Instead, it will argue that criminal penalties aren’t the right way to address a drug that many scientists rate as minimally dangerous.

“Psilocybin is safer than cannabis. Cannabis is safer than alcohol. There’s no reason for us to be criminalizing individuals and spending taxpayer money,” Matthews said.

But his most prominent critic says the initiative is a sneaky step toward full legalization and sale of the drug.

“It kind of feels like we’re the last ones in Colorado who are opposed to drug legalization, or decriminalization,” said Jeff Hunt, director of the conservative Centennial Institute at Colorado Christian University.

Hunt is amenable to the argument that criminal consequences might do more harm than good, but he sees this measure as a step toward another legal drug industry.

“That’s my concern about psilocybin,” he said. “We’re setting up the argument for commercialization.”

A long history

The history of psilocybin mushrooms dates back “at least hundreds and likely thousands” of years in Central and South America, according to one study. Encounters with the drug are recorded in the works of Spanish friars traveling through Central America during the 1500s — and the colonizers later outlawed the fungus and drove its use underground.

The subject was all but ignored by Western science until the 1950s, when Americans were admitted to secret ceremonies, launching a new, intensive study of the drug. LSD and psilocybin were studied and sold commercially into the 1960s — but they were classified as “Schedule 1,” the most restricted category of drugs, when the United States’ modern drug laws were created in 1970.

Research into the substances disappeared over the subsequent years, with the last legal dose of psilocybin administered in 1977 in Maryland, according to Michael Pollan’s new book, “How to Change Your Mind.”

The modern age began in 1999, Pollan writes, as federal authorities approved a new research regime at Johns Hopkins University. In the 20 years since, hundreds of people have taken legal doses in controlled settings.

One small study from the university found remarkable results for cigarette smokers: After a combination of behavioral therapy and psilocybin doses, 60 percent quit smoking for at least 16 months — compared with success rates around 30 percent for medications. Another found that guided psilocybin experiences produced “substantial spiritual effects,” with an increased sense of well-being and life satisfaction lasting more than 14 months for most subjects.

There is no evidence of physical dependence or withdrawal among users. The drug is consistently rated by users and experts as one of the least harmful drugs, according to a Johns Hopkins paper published in Neuropharmacology.

But the drug also can have a dark side. While people in controlled settings report overwhelmingly positive experiences, trips can go wrong in the real world.

One survey found that people who have a bad trip on mushrooms often rate it as one of the worst experiences of their life, including three suicide attempts among about 2,000 respondents. And Johns Hopkins researchers have cautioned against giving hallucinogens to people who are at risk for serious mental disorders.

“There’s a small but real percentage of the population, 1 or 2 percent, that have active psychotic disorders, or they have a good predisposition to develop psychotic disorders,” said Dr. Matthew Johnson, who has researched psilocybin for 15 years at Johns Hopkins. “It’s very clear those people should not be exposed to psychedelics like psilocybin.”

The cannabis comparison

Voters may approve the measure, but there’s one big question: Would it matter? Would the local government listen?

Denver voters approved marijuana decriminalization measures in 2005 and 2007, but the police kept enforcing the law. “I think the city continued on its merry way,” said Way, of Drug Policy Alliance. Still, those votes helped build public support for legalization, advocates say.

The psilocybin proposal does try something new: It bans the city from using its money and other resources to enforce mushroom penalties.

Denver District Attorney Beth McCann does not support the initiative, although she would like to see the issue studied more.

“Until we have had a longer period to learn more about the impact of marijuana legalization, I do not support the legalization of another federally-banned substance,” she said in a written statement.

And she would prefer a statewide effort to a municipal one, she said. Mayor Michael Hancock does not support the ballot measure, and Attorney General Phil Weiser declined to comment.

Meanwhile, campaigners in Oregon are taking a different approach. Their statewide ballot measure for 2020 would allow people to use the drug at licensed facilities.

Kevin Bommer, deputy director of the Colorado Municipal League, said the Denver mushroom effort looks pretty small in comparison.

“It’s just a single-city issue right now, and we’ll see what happens after it passes,” he said. “After marijuana, I thought I knew everything — there wouldn’t be anything more.”