Many more volunteers are needed, says the nonprofit medical-research group leading the study.
The California-based Multidisciplinary Association for Psychedelic Studies (MAPS), founded in 1986, is conducting the study with the help of a $2.16 million grant from the Colorado Department of Public Health and Environment.
Over the next two years, the study will "evaluate the safety and efficacy of four different potencies of marijuana to manage symptoms of PTSD in 76 U.S. veterans," a MAPS news release states.
The first participant in the study used cannabis on Monday at a north Phoenix clinic.
Marcel Bonn-Miller of the University of Pennsylvania's Perelman School of Medicine is the study's principal investigator. Dr. Sue Sisley, a local M.D. who was fired from the University of Arizona, is the co-investigator.
Half of the volunteers will take part in the study in Arizona, while the other half will be tested at John Hopkins University in Baltimore.
Researchers believe the results of the study could lead to Federal Drug Administration approval of whole-plant marijuana as treatment for PTSD.
Sisley, who helped pioneer the project, was fired in 2014 after a conservative Republican lawmaker complained about her medical-cannabis advocacy.
Her interest in medical marijuana started early in her career. While working with veterans as a psychiatrist, she became convinced that anecdotal reports of marijuana relieving PTSD symptoms might have merit.
PTSD affects up to 20 percent of Iraq War veterans and about 15 percent of Vietnam War veterans, according to the U.S. Department of Veterans Affairs.
She and researchers at MAPS produced a 61-page scientific protocol to serve as a template for the research. Then, they began the arduous process of obtaining funding and federal approval.
Another big problem would be obtaining the weed for the study. The only marijuana that the federal government considers legal is grown on a 12-acre farm run by the National Center for Natural Products Research at the University of Mississippi.
In order to get that pot to the study, MAPS had to negotiate approval from U.S. Health and Human Services and the Drug Enforcement Administration.
They also had to find the perfect location for the study. Sisley wanted it conducted at the University of Arizona, where she held a part-time job.
At the time, UA officials said they wanted to land the PTSD-marijuana study, but not if Sisley was involved.
Meanwhile, 110,000 vets signed an online petition supporting the Arizona doctor.
MAPS decided to stick with Sisley and look for a different location.
She started a company in 2015 called Scottsdale Research Institute, which currently rents space for the study at a empty warehouse.
In April, the DEA finally approved the study and cleared the path for the Mississippi marijuana to be tested on veterans.
The veterans will be tested on four kinds of marijuana. One is a placebo — a strain of marijuana that contains no THC, the plant's primary psychoactive chemical. Two strains will contain THC, at 6 and 12 percent. A fourth strain contains 6 percent cannabidiol, a constituent of marijuana believed to have medicinal value.
Volunteers smoke up to two joints' worth of marijuana every day from small pipes. Later, they'll self-administer marijuana at home on video.
The study requires 17 clinic visits over 12 weeks and a six-month follow-up visit, plus drug screenings to determine the THC levels in the vets' bloodstreams.
"We're just so grateful to finally enroll patients," Sisley told New Times on Friday. "This has been our dream that started seven years ago, to study whole-plant cannabis in this most-deserving population of veterans ... The government thought they could stonewall us until we got tired or walked away. But we're committed to doing this."
She credited activist veterans for their efforts over the years in lobbying politicians and bureaucrats to allow the study.
Now that it's up and running, though, finding participants is the new challenge. It's not easy to find qualified people because of rigorous criteria that helps ensure scientifically valid results.
Only two veterans of the 38 needed for the Phoenix portion are formally enrolled. Another 10 are "on deck" for a final evaluation, Sisley said.
More than 300 veterans total have been "screened out" since the study began actively seeking volunteers earlier this year, she said.
The study requires people who have been diagnosed with PTSD, preferably those whose conditions have resisted traditional treatments. Light and "irregular" users of marijuana, or nonusers, are also preferred, she said, adding that "dependent," daily users are not eligible.
Sisley and others working on the study have been going out to American Legion or VFW halls to find their study subjects.
The one place with the most eligible PTSD users, the Phoenix VA Health Care System, won't allow any presentations or advertisements about the study, Sisley said.
blocked Sisley in May from giving a talk about the study at the Phoenix VA hospital.
"It's really unconscionable, and really speaks to their lack of commitment to science," she said. "I'm just asking them to allow us to hang up fliers, or at most a simple lecture to their medical staff. None of that is allowable."
Paul Coupaud, spokesman for the Phoenix VA, said the VA doesn't promote, and can't endorse, any outside research. Beyond that, the VA doesn't allow doctors to "promote, prescribe, or discuss marijuana with veterans," he said.
Would-be volunteers don't have to rush — they have plenty of time to sign up for the two-year program. Sisley estimates she'll need to screen more than 1,000 vets to round out the 38 for the Phoenix portion.
The state Department of Health Services added PTSD as a qualifying ailment to the state's program in 2014.
MAPS asks anyone interested in being a volunteer with the study in Phoenix to email email@example.com. For the Baltimore location, call (410)550-0050.