Thousands of people are expected to attend a conference this week organized by a psychedelic advocacy group, even as some worry about the “normalization” of hallucinogenic drugs in the eyes of young people following their legalization in Colorado.

The conference — which is bringing together an unlikely cohort of speakers, including an NFL star, a former Republican governor and a rapper — is occurring roughly six months after Colorado’s voters narrowly split to pass a ballot measure that decriminalized possessing, growing, sharing and using psychedelic substances by adults.

Among the conference speakers are NFL quarterback Aaron Rodgers, who’ll soon debut with the New York Jets after years with the Green Bay Packers. Rapper and actor Jaden Smith, the son of Will Smith, will speak, too, as will former Texas Republican Gov. Rick Perry, who is an advocate for researching psychedelics’ potential benefits for veterans experiencing PTSD.

Psychedelics remain illegal at the federal level, though they have been gaining acceptance in some quarters and interest in studying their potential benefits has grown.

Just six years ago in Oakland, California, the Multidisciplinary Association for Psychedelic Studies held a conference with roughly 3,000 attendees and a smattering of lesser-known speakers and die-hard proponents.

This time, organizers estimated at least 10,000 attendees.

Rick Doblin, founder of the advocacy group, kicked off the conference Wednesday in front of an overflowing theater espousing grandiose goals, such as “net-zero” trauma by 2070 through the use of psychedelics.

The American Psychiatric Association has not endorsed the use of psychedelics in treatment, noting the Food and Drug Administration has yet to offer a final determination. The FDA did designate psilocybin as a “breakthrough therapy” in 2018, a label that’s designed to speed the development and review of drugs to treat a serious condition. MDMA, often called ecstasy, also has that designation for PTSD treatment.

Alton P. Dillard II, who speaks for One Chance To Grow Up, said his group’s primary worry is the perception — especially to kids — that psychedelic substances are now less harmful because they have been legalized for adult use. One Chance To Grow Up did not take a position on the psychedelics proposal that Colorado voters approved, 54%-46%, last November.

Adults and the psychedelic industry must be “hypervigilant to ensure that the perception of harm to kids doesn’t lessen due to psychedelics being legal under certain circumstances,” Dillard said.

“We have the responsibility to learn from medical and recreational marijuana that these products should not be normalized in the eyes of youth,” he added, noting the limited data on psychedelics.

Jesse Bedayn of the Associated Press and Luige del Puerto of the Denver Gazette contributed to this article.