More than a decade after voters here first said marijuana could be medicine, Colorado is preparing to embark on the largest state-funded effort to study the medical benefits of cannabis.

Under a bill signed this year by Gov. John Hickenlooper, the state health department will give out about $9 million in grantsin the next five years to researchers for marijuana studies. Most importantly, the research is expected to include clinical trials on the kinds of marijuana products actually being used in Colorado — something that federally funded studies on marijuana have lacked.

“Our intent is to be rigorous scientifically, but to also act with some expediency because these are products that a large percentage of our population is using today,” said Dr. Larry Wolk, the executive director and chief medical officer of the health department. “We want to make sure that what’s happening out there in everyday practice isn’t harming people.”

Nearly 20 years after California became the first state in the U.S. to pass a medical marijuana law, the research on marijuana’s health effects is still largely polarized.

Several studies — matching the anecdotal experiences of medical marijuana patients — have found cannabis or its isolated components can be effective in managing pain, tremors, nausea, inflammation and other conditions.

Other studies, though, have taken a dimmer view of marijuana, summed up by a new National Institute on Drug Abuse review, published in the New England Journal of Medicine, that concludes marijuana is bad for brain development and can lead to addiction. Although the review says marijuana may have therapeutic potential, it finds the evidence less than convincing.

“Some physicians continue to prescribe marijuana for medicinal purposes despite limited evidence of a benefit,” the review states. “This practice raises particular concerns with regard to long-term use by vulnerable populations.”

Complicating the analyses further is that many studies use cannabis grown by a government-contracted lab — not the kind of sophisticated, and often more potent, products developed by the medical marijuana industry across the country.

California attempted to solve this riddle last decade by becoming the first state to fund medical marijuana research. More than 12 years and $8.7 million later, the state’s Center for Medicinal Cannabis Research published studies finding that smoked marijuana could relieve pain at certain doses, that vaporized marijuana was safer on the lungs, that medical marijuana patients with multiple sclerosis reported reduced spasticity and other findings.

Colorado is now attempting to build on that research. The money for the grant program will come from registration fees paid by medical marijuana patients.

Wolk said the health department is assembling the oversight committee that will review grant applications. He hopes to begin accepting applications in the second half of 2014, with funding for studies going out in early 2015. He expects the state will be able to fund 10 to 15 studies.

Wolk said research on the medical conditions approved for marijuana use in Colorado would take priority. But he said the state also would consider funding other types of studies — even local clinical trials on pharmaceutical drugs derived from marijuana.

“We’re trying to turn over all the stones on this,” he said.

Dr. Christian Thurstone, an adolescent addiction medicine specialist at the University of Colorado, said he hopes to apply for a grant to study whether a nonpsychoactive marijuana compound called CBD can help treat people addicted to cocaine, opiates or even pot. Earlier studies have suggested it could.

Thurstone, who has often expressed concerns about marijuana legalization, said it is important for the state to fund research on cannabis, in part because the federal government is falling behind. Since 2003, the amount of money the National Institutes of Health has given out in grants for all research has remained basically unchanged, when adjusted for inflation.

“We have to look at other ways to keep our research infrastructure going,” Thurstone said.

John Ingold: 303-954-1068, jingold@denverpost.com or twitter.com/johningold