NEW YORK (TheStreet) -- Doctors are increasingly frustrated about federal marijuana restrictions standing in the way of important research.

"It is troubling that while few barriers exist for parents to give their children marijuana in Colorado, there are significant federal roadblocks preventing doctors from studying it in a rigorous scientific manner," write Orrin Devinsky and Daniel Friedman, physicians at the Comprehensive Epilepsy Center at New York University in The New York Times Wednesday.

The two doctors voiced skepticism about many of the perceived medical benefits of marijuana, and argued that "the recent wave of state legislatures considering and often approving medical marijuana raises significant concerns."

At the same time, however, they state that the government's classification of marijuana as a "schedule 1" drug places severe restrictions on their ability to study the effects of its active ingredients, including the chemical compounds cannabidiol, or CBD, and tetrahydrocannabinol, or THC.

"While it is possible to study Schedule 1 drugs in a controlled laboratory setting, it is extremely difficult to study these substances in patients. For our study, we keep the CBD in a 1,200-pound safe in a locked room, in a building with an alarm system," the doctors write.

Similar frustration came through in an article in the latest issue of The New York Review of Books by Harvard Medical School Professor Jerome Groopman, a longtime staff writer for The New Yorker magazine.

While Groopman's article tended more toward information than opinion, he appeared to be more excited than the NYU doctors about the potential medical benefits from marijuana and related drugs. Still, he wrote that as a physician prescribing therapy for patients, he is in "an uncomfortable situation," since even in the 20 states where medical marijuana is legal, it "is regulated like a supplement rather than a drug," with "no standardization of optimal amounts of psychoactive THC and nonpsychoactive CBD."

Proposed legislation, including a bill introduced Wednesday by Steve Cohen (D.-Tenn.) would ease restrictions on medical research involving marijuana.

And Cohen was one of 18 members of Congress who sent a letter to President Obama Wednesday urging him to remove marijuana from the list of schedule I and II drugs. Marijuana is currently a schedule I drug, meaning federal laws regard it as more dangerous than cocaine, which is schedule II. The state and party affiliation of the signers, however, allude to the significant political obstacles to marijuana liberalization at the federal level. Seventeen signers are Democrats and only one, California Rep. Dana Rohrabacher, is a Republican.

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