Scientists who study medical marijuana will soon have access to a wider variety of strains. The National Institute of Drug Abuse (NIDA) — the federal "dealer" that supplies the drug to scientists — has received numerous complaints from researchers that the drug they supply is too weak compared with what's sold on the streets, legal or otherwise. But the complaints aren't responsible for the change, Nature reports. NIDA's willingness to expand the types of plants available to researchers is tied to the fact that legal marijuana is becoming increasingly available.

"We want to be able to evaluate the claims that marijuana is therapeutically beneficial."

"We want to be able to evaluate the claims that marijuana is therapeutically beneficial," Nora Volkow, director of NIDA in Rockville, Maryland, told Nature.

The pot that NIDA gives to qualifying research groups is grown at the University of Mississippi. In 2014, the farm increased production from about 40 pounds to more than 1,300 pounds, and NIDA increased its spending on research marijuana by 50 percent. The University of Mississippi also started growing two new strains of marijuana, which will be available to researchers soon. One of them contains high levels of cannabidiol, a substance that isn't hallucinogenic but that appears to have therapeutic effects. This should allow researchers to evaluate pot's ability to reduce pain, for instance.

Despite this change, the University's plants still aren't as strong as the stuff you can get elsewhere. NIDA's strongest pot contains 12 percent THC — pot's primary psychoactive component — whereas most of the pot that's seized by the DEA contains 20 percent THC.

Moreover, researchers have to jump through a number of hoops to get their hands on the expensive plants. NIDA currently charges scientists $7 per cigarette — far more than the clinical-grade pot grown in Canada and Israel, Nature reports. And the application process is so long that the Colorado government asked the US federal government if it would allow universities in the state to grow their own pot for research. Colorado legalized recreational marijuana in 2012, but because the drug remains illegal under federal law, researchers in Colorado can't use it in their research.

NIDA's monopoly on research marijuana may be coming to an end, however. Legislation backed by Republicans and Democrats alike was introduced in the US Senate on March 10th. The bill would let at least three more FDA-approved institutions cultivate marijuana for research purposes. The bill would also get rid of the review process that can add years to a study's approval time.