The largest organization representing psychology professionals in the United States is calling on the federal government to expand the legal supply of marijuana for use in scientific research.

In a letter addressed to Attorney General William Barr, the American Psychological Association (APA) is requesting that the Department of Justice immediately evaluate the more than two dozen applications for cannabis cultivation licenses that stalled under his predecessor Jeff Sessions.

“The scientific community is eager to advance cannabis research on both the harmful and therapeutic effects of cannabis and its derivatives,” APA President Arthur Evans Jr. wrote on Wednesday. “Without access to an expanded range of cannabis products engineered under [Food and Drug Administration]-approved Good Manufacturing Practices, scientific research cannot hope to keep pace with the ever-expanding recreational and medicinal cannabis marketplace.”

Cannabis and its constituent compounds are of significant interest to psychological scientists, both to those interested in use, abuse and dependence, as well as to those interested in using marijuana and its derivatives to treat health conditions.

But for the past half century, all marijuana for use in federally authorized research has been supplied by a single facility at the University of Mississippi. Scientists have complained that it is difficult to obtain product from the school, however, and that its quality is often less than ideal.

Evans called the current system “costly, cumbersome and limited by a sole source supply.”

“[W]e urge you to take immediate action on the existing pool of cannabis grower applications so that our nation’s scientific community can continue to expand the study of both the harmful and potential therapeutic effects of cannabis and its derivatives.”

Addressing those concerns, the Drug Enforcement Administration established a formal application procedure in 2016 to license additional cultivators.

Since then, at least 26 applications have been received, but the Department of Justice has refused to process them, a situation that led frustrated lawmakers to send a series of bipartisan letters pressing Sessions to act. Senators from both sides of the aisle called on the then-attorney general to stop blocking efforts to increase research and, in committee hearings, Sessions said he was supportive of allowing more people to grow marijuana for research purposes.

But the applications never moved under his tenure.

The letter from APA, which has more than 118,000 members, asks Barr to “take immediate action to facilitate critically needed cannabis research by evaluating the more than two dozen cannabis grower applications that have languished for over two years at the Department of Justice.”

Barr said last month in written testimony to senators that he supports “the expansion of marijuana manufacturers for scientific research consistent with law” and pledged to “review the matter and take appropriate steps.”

In September, the House Judiciary Committee approved legislation designed to force the Justice Department’s hand by requiring it to issue additional licenses. The bill died after it didn’t receive a floor vote, but its sponsor, Rep. Matt Gaetz (R-FL), refiled a new version in January following the start of the 116th Congress.

In a letter to U.S. AG William Barr, APA CEO @ArthurCEvans calls for immediate action to evaluate existing applications from cannabis growers so researchers can continue to expand the study of harmful & therapeutic effects of cannabis & its derivatives: https://t.co/M20btHwYgX pic.twitter.com/hI6u2HCU6E — American Psychological Association (@APA) February 27, 2019

Evans, of APA, said that the current limited supply of marijuana available for research isn’t particularly useful in evaluating the effects of the the type of cannabis products that are now available to consumers under the laws of a growing number of states.

“While [the National Institute on Drug Abuse] provides a staple catalog of cannabis products and derivatives for research, it cannot keep pace (nor should it be expected to) with the range of products available to consumers in the 10 states that have approved recreational cannabis use or the 34 states distributing cannabis products through medical dispensaries,” he wrote in the new letter to Barr.

Evans cited a 2016 NIDA request for information that asked the scientific community about topics of interest for further cannabis research. The most consistent recommendation was to have marijuana strains and products available that reflect the diversity available at state dispensaries.

“That would include cannabis strains and hybrids with higher tetrahydrocannabinol (THC) content, more reflective of what is found in state programs (up to ~30 percent THC), as well as increasing the number and variety of cannabis chemotypes to include not only a range of THC concentrations, but also other cannabinoids: cannabidiol, cannabigerol, cannabinol, cannabichromere, tetrahydrocannabivarin, terpenes (e.g., linalool, terpinolene, nerolidiol, myrcene) and flavonoids with varying ratios of each to better isolate and characterize their constituent pharmacological effects,” Evans wrote

“There is also increasing demand to improve the quality of placebo cannabis because the current process for its manufacturing removes not only THC but many other compounds, including other cannabinoids as well as volatile compounds (terpenes) that contribute to the color and olfactory characteristics,” he added. “A more effective placebo would better mimic the taste, smell and look of active cannabis.”

Evans wrote to Barr that scientists also need access to an “expanded range of formulations for varying routes of administration to reflect what is available in state dispensaries, including for oral, sublingual, respiratory, rectal and dermal delivery of purified and whole plant extracts along with matching placebo formulations (e.g., edibles, hash oil, budder, wax and shatter).”