Residents in the Colorado capitol city of Denver will vote in May to legalize hallucinogenic mushrooms, after the referendum received a green light from officials on Friday.

In a US state that has notably legalized cannabis for both medicinal and recreational purposes, Colorado's most densely-populated region will now see the opportunity to add psilocybin mushrooms to the list of decriminalized chemical compounds.

The Denver Psilocybin Mushroom Decriminalization Initiative (DPMDI), scheduled for a May vote, will seek approval for an ordinance that will make it legal to possess the naturally-occurring substance — regardless of how much — as long as you are 21 or older, according to Nbcnews.com.

If passed, the initiative would also allow users to grow their own psychedelic mushrooms, although the move does not legalize retail sales of the compound.

Officials with Denver's Elections Division reviewed a widely-circulated petition and found that enough valid signatures had been submitted, triggering the addition of the DPMDI initiative to the May 7 Municipal Election city ballot.The DPMDI initiative campaign director, Kevin Matthews, noted that the vote will be America's first attempt to decriminalize psilocybin, adding that Denver is the right place to offer the referendum.

"We're a pretty progressive city when it comes to drug policy," Matthews said, cited by NBC News.

Although political observers do not give the May vote a high chance of passing, the move will nonetheless work toward destigmatizing hallucinogenic mushrooms now being used in clinical studies as a means of countering various forms of mental illness, including post traumatic stress disorder (PTSD)."I don't foresee a recreational cannabis model in the near future," Matthews noted, adding that he intended the campaign to educate people and end the criminalization of its use at the hands of clumsy US policies from the 20th century's War on Drugs.

While offering the legalization of psilocybin, the measure will also seek to end criminal penalties connected with its use and possession.Matthews acknowledged that the 2014 decriminalization of the recreational use and sale of marijuana in the state has gone a long way toward relaxing a public perception frightened by heavy-handed federal drug tactics.

"In some ways marijuana did open the door," he observed.

Researchers note successful new techniques using psilocybin and other former recreational — or ‘party' — drugs that are in the trial stages to treat depression anxiety and other mental challenges.

"I speak firsthand to how intense these experiences can be," remarked Johns Hopkins University School of Medicine psychiatry and behavioral sciences professor Matthew W. Johnson, who has long researched the use of psilocybin to treat anxiety and depression in cancer patients facing the end of their lives.

Psilocybin researcher Charles Grob, a UCLA psychiatry professor, agreed with Johnson's assessment and advocated further study and access to educational resources.

"If, in fact, it's ever available on a mass basis, it would be imperative to have a strong education component so people could understand what these compounds are," Grob stated, adding, "They should not be treated in a trivial manner."