A new study has emerged alleging that the Drug Enforcement Administration has been obstructing the medical research of marijuana for nearly half of a century to prevent the reclassification of the drug from its current harmful designation.

Released by the Multidisciplinary Association for Psychedelic Studies and the Drug Policy Alliance, "The DEA: Four Decades of Impeding and Rejecting Science" study revealed that the agency has held an "unjustifiable" monopoly over research grade marijuana preventing federally approved research, Al Jazeera America reported.

On Wednesday during a teleconference, DPA Executive Director Ethan Nadelmann called for an end to the DEA's authority over the substance, which is currently labeled as a Schedule 1 drug, meaning it's a dangerous drug with no medical value.

"The DEA impedes research by abusing its discretionary powers over the scheduling process, making it difficult to obtain marijuana for research purposes," Nadelmann said. "We recommend taking away the DEA's power over the drug scheduling and access to drugs for research."

According to the study, medical marijuana advocates demand that the DEA reclassify marijuana as a Schedule 2 drug, which would open up more medical research for it and give the Food and Drug Administration the authority to regulate it, Al Jazeera reported.

The study also found that DEA administrative law judges, who evaluated the evidence of rescheduling marijuana, recommended the reclassification but the agency has done nothing. Despite the scientific research that has been done, the agency has continued to ignore it and insists there is not enough evidence to support a reclassification.

Carl Hart, a professor at Columbia University's department of psychology and psychiatry, said during the teleconference that DEA's claims are baseless. He also noted that he has studied the drug for several years and has found the research to be promising.

"This concerns me greatly as someone who has studied marijuana and given thousands of doses of the drugs. All studies have shown potential," Hart said.

"The notion that the DEA has not thought about reconsidering scheduling of marijuana seems to be against scientific evidence and what we're trying to do as a society that relies on imperial evidence to make decisions."