Attorney General Eric Holder’s recent comments calling for reform of long mandatory sentences for low-level drug offenders have opened a floodgate of mixed reactions. His comments have also fast-tracked arguments about legalization of marijuana.

Holder’s comments, coupled with CNN chief medical correspondent Sanjay Gupta’s recent reversal of his objections to medical marijuana have reignited the national conversation about the controversial drug. In some quarters it appears the cultural attitude toward marijuana is shifting in favor of legalization, particularly for medical use.

A cadre of experts from the scientific community are adding credibility to the uphill battle to legalize the drug for medicinal use. Chief among them is Sunil Aggarwal, M.D., Ph.D., a resident in physical medicine and rehab. Aggarwal’s support of cannabis was bolstered by his own study of 176 patients who suffered chronic pain and were treated with cannabis.

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“For 139 of them, I did a retrospective, and the bottom line is a wide variety of chronic pain syndromes were being well-managed using cannabis,” Aggarwal said. “In several cases there was a reduction of other drugs to manage chronic pain, or a reduction in dosages of these drugs. Nobody showed any adverse effects from this drug.”

Aggarwal, who has become a high profile voice in the fight to legalize cannabis for the treatment of pain, says other countries are way ahead of the United States on this issue.

“If you look across Western Europe, South America and even India, there is widespread use,” said Aggarwal. “It has been legal in parts of this world for a long time. We are catching up to the recognition of its uses that has long been known elsewhere. Ultimately we need a sound public health policy for both medicinal usage and as a relaxant for social usage of cannabis.”

One problem is the historical stigma the drug carries that is hard to overcome via state and federal laws. Even today, when some states have legalized marijuana, individuals who operate cannabis-related businesses meet up with roadblocks, said Betty Aldworth, deputy director of the National Cannabis Industry Association, a trade group that represents nearly 300 cannabis-related businesses at the federal level.

“I think it’s safe to say that things like Gupta’s change of heart and Holder’s statements are reflective of a broader shift in the public’s view of marijuana,” Aldworth said. “Through polling we know that the vast majority of Americans believe patients should have access to medical marijuana, and that a slim majority of Americans support adults being able to choose whether or not they would like to use it. Once we realize that, it is not too far a step to say that marijuana should be provided by licensed, responsible businesses.”

A budtender pours marijuana from a jar at Perennial Holistic Wellness Center medical marijuana dispensary, on July 25, 2012 in Los Angeles.David McNew/Getty Images

The glitch in that step has to do with taxation, Aldworth said. “In section 280E of a 1980s tax code, it states that you cannot take small business deductions from your taxes for activities involved in trafficking illegal products. While other businesses are taxed between 15 and 30 percent, marijuana providers are punished with federal tax rates that reach up to 80 percent.”

That means that even if a state legalizes marijuana, businesses are still subject to stringent federal tax guidelines.

“It’s important for the public to understand that as we shift from a culture that keeps marijuana underground and forces it in the hands of cartels and criminals, to a culture that allows patients to access their medicine safely in a secure facility, that these business owners are really participating in important ways in their state economies,” Aldworth said.

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Still, there are detractors in high places who base their objections to legalization on scientific evidence.

“Studies show that 9 percent of those exposed to marijuana will become addicted,” said Nora Valkow, M.D., Director of the National Institute on Drug Abuse at the National Institutes of Health. “If you are less than 17 or 18 years old, that goes up to 16 percent.”

Even for the majority of teens who do not become addicted, Valkow says there are additional known health risks.

“My main concern with marijuana is the potential detrimental effects it can have on the developing human brain,” she said. “Exposure in adolescence can ultimately affect cognitive performance, mood and motivation and drive. Marijuana can also have adverse effects on adults. If you are taking it with a high content of THC it can make you psychotic.”

As for legalizing marijuana for the treatment of pain, Valkow says the idea is premature.

“We have to learn from history,” she said. “There’s a lot of excitement that the drug is benign and can be a panacea for a wide variety of diseases. But research much be done. The concept of legalizing marijuana for pain is one that would need randomized clinical trials that evaluate what concentrations of the active ingredients of marijuana are necessary for the optimal control of pain. What are the doses? None of that work has been done.”