By Pat Anson, PNN Editor

A federally funded review of plant-based treatments for chronic pain has yet to find adequate clinical evidence on the benefits or harms of kratom, an herbal supplement used by millions of Americans to relieve pain, anxiety, depression and other medical conditions.

In an update released this week, researchers at Oregon Health & Science University (OHSU) reported that some cannabis products provide small to moderate pain relief, a finding based on a systematic review of two dozen clinical trials of cannabis.  But no similar studies were found to support the use of kratom or any other plant.   

“No evidence on other plant-based compounds, such as kratom, met criteria for this review,” researchers said.

OHSU was awarded a contract last year by the Agency for Healthcare Research and Quality (AHRQ) to review the evidence for cannabis, kratom and other plant based treatments for chronic pain.  

Kratom comes from the leaves of the mitragyna speciosa tree in southeast Asia. Although it has been used for centuries as a natural stimulant and pain reliever, few clinical trials have been conducted to test kratom’s efficacy or safety. The few studies that have been conducted were excluded by OHSU researchers due to their size, methodology or because they weren’t published in English.

For example, a 2020 Malaysian study that found kratom provided “a substantial and statistically significant increase in pain tolerance” was excluded because the young men who participated in the one-day trial were considered an “ineligible population.” OHSU researchers excluded all studies lasting less than 4 weeks.

“Setting aside the disappointment that AHRQ does not appear to be taking the purpose of the review of plant-based compounds very seriously, the conclusion that there is no evidence to support the effects of kratom on chronic pain is absurd,” said Mac Haddow, a lobbyist for the American Kratom Association.  “It’s like denying that Chicago is a windy city because the instrument that was selected for assessing wind speed was not used.”

Haddow said the AHRQ review should be expanded to include survey results from kratom users, animal studies and other types of research that don’t rise to the level of a clinical trial.

“The review appears to be excluding any research that is not a pharmaceutical development clinical trial model that would involve controlled kratom administration in a full-blown human clinical trial,” Haddow told PNN. “The deeply embedded bias against plant-based compounds that offer potential values for addressing the opioid crisis — or even providing a non-addictive and safer alternative for the management of acute and chronic pain should be a priority for the AHRQ.”

This isn’t the first time the quality of federal research into the safety and efficacy of kratom has been questioned. In 2018, the Department of Health & Human Services quietly withdrew an FDA request to classify kratom as a Schedule I controlled substance because of “lack of evidence” it can be abused or posed a public health threat. A former HHS official recently said the FDA’s recommendation was rejected because of “embarrassingly poor evidence & data.”

$2 Billion in Federal Grants

A final report on plant-based treatments for chronic pain is expected in August. As PNN has reported, OHSU researchers have recently conducted a series of reviews on a wide variety of pain therapies for the AHRQ, which are being used by the Centers for Disease Control and Prevention to revise and possible expand its controversial 2016 opioid guideline.   

Much of that research is being led by Dr. Roger Chou, a primary care physician who heads the Pacific Northwest Evidence-based Practice Center at OHSU.  Chou, who co-authored the CDC opioid guideline, is a prolific researcher who has collaborated on several occasions with members of Physicians for Responsible Opioid Prescribing (PROP), an advocacy group that seeks to reduce the use of opioid medication.

The contract on plant-based pain treatments is potentially worth up to $1.4 million for OHSU, a public research university that the federal government often turns to for medical research. According to the website GovTribe, in the last five years OHSU has been awarded nearly $2 billion in federal research grants to study everything from cancer and contraceptives to Alzheimer’s and Parkinson’s Disease.

OHSU paid $1.3 million back to the government to settle allegations that it misused grant money in its primate research center. Although the settlement was reached in 2018, it was not made public until recently in an Inspector General’s report, according the animal rights group Rise for Animals.