Earlier this month, the United States Supreme Court ruled that federal drug laws trump policies in ten states that permit medicinal marijuana use. The decree reignites a smoldering debate among scientists, activists, and lawmakers about how to leverage marijuana’s medical benefits while minimizing its potential for abuse.
Known by the scientific name Cannabis sativa, marijuana is an annual herb closely related to the hops used in beer brewing.
Cannabis has been “used since antiquity for both herbal medication and intoxication,” according to a 1999 study commissioned by the Institute of Medicine (IOM), a Washington, D.C.-based component of the National Academy of Sciences.
“There is scientific evidence that [marijuana] helps with pain relief and nausea and vomiting from chemotherapy, for example, in terminal cancer patients,” said John A. Benson, Jr., a principal investigator of the IOM study and a professor of internal medicine at the University of Nebraska Medical Center.
In addition, some HIV/AIDS patients suffering from decreased appetites use marijuana to “get the munchies,” another oft-noted effect of the drug.
Roger Pertwee, a professor of neuropharmacology at the University of Aberdeen’s Institute of Medical Sciences in Scotland, noted that “cannabis contains lots of different chemicals called cannabinoids.” The most active chemical is delta-9-tetrahydrocannabinol, or THC.
THC binds to specific receptors in the human brain to create the euphoric high associated with smoking pot.
In the early 1990s Pertwee’s research group helped to uncover human-produced chemicals similar to THC that stimulate our appetites and help us control pain. “We produce our own cannabis, in effect,” he said. “It often seems to have a protective role.”
According to Benson, of the University of Nebraska Medical Center, the debate should not be about whether marijuana works to relieve symptoms, but how to best deliver its chemical constituents.
“Smoking is a terrible delivery system,” he said. Aside from the potential risk of lung damage, the potency of smoked marijuana is difficult to measure, because THC levels vary widely from plant to plant.
Currently, a synthetic version of THC is available to cancer and HIV/AIDS patients in the U.S. as an oral drug known by the brand name Marinol. Approved by the U.S. Food and Drug Administration, the drug (dronabinol) allows patients and doctors to control the amount of active compound that is delivered.
Benson noted, however, that some patients prefer smoking pot to taking pills because the effects set in much faster. “When you inhale something into the lungs, it’s very rapidly absorbed—you get an effect in five minutes,” he said. “When you take a capsule, it may take an hour and a half.”
THC drugs would be more effective, Benson added, if they were delivered through a fast-acting oral spray similar to asthma inhalers.
According to the 1999 IOM report, the legal status of marijuana has greatly colored the scientific debate over the plant’s use in medicine.
The broad U.S. federal drug law known as the Controlled Substances Act of 1970 lists marijuana as a Schedule I substance. The designation describes drugs with a high potential for abuse and no accepted medical use. Other Schedule I drugs include heroin and LSD.
In 1972 the National Organization for the Reform of Marijuana Legislation, a nonprofit advocacy group, unsuccessfully lobbied the U.S. government to relist marijuana as a Schedule II substance. That class includes drugs such as morphine and cocaine that are highly addictive but have well-established medical uses.
Based on the IOM study, the U.S. Drug Enforcement Administration (DEA) maintains that smoked marijuana should remain a Schedule I drug. Any medical effects from smoking marijuana cigarettes can be met more effectively with approved commercial drugs, the agency says.
In fact, DEA has placed the THC drug Marinol in Schedule III—a less restrictive category—and supports research to find new delivery methods and therapeutic uses for cannabinoids.
Pertwee, of the University of Aberdeen, believes the potential for patients to become addicted to manufactured cannabinoid drugs is relatively low. However, conflicting data exist as to whether long-term THC use leads to dependency.
Benson also believes that medical marijuana, even when smoked by terminal patients, is unlikely to trigger addiction if use remains carefully monitored. “If you have a controlled distribution system for medical use, as with morphine, for example, I don’t see the risk,” he said.
It’s now legal to use marijuana to treat certain medical conditions in 25 states, but the Food and Drug Administration has still not approved the marijuana plant as a treatment for any disease or health issue. That’s because there haven’t been enough large studies of the drug to show that its benefits outweigh the risks in patients who use it, said the National Institute on Drug Abuse (NIDA). And in order to gain approval, researchers also need show that marijuana is safer or more effective than existing treatments for certain conditions.
Nevertheless, scientists have good reason to think that the marijuana plant could be useful in treating a number of medical conditions. The active ingredient in marijuana, delta-9-tetrahydrocannabinol (THC), has been shown to increases appetite and reduces nausea. Another chemical in marijuana, cannabidiol (CBD), may decrease pain and inflammation and help with muscle-control problems, according to NIDA. Both THC and CBD belong to a group of chemicals called cannabinoids.
Live Science has rounded up the promising evidence that medical marijuana may help people with certain conditions. Here’s what we found:
Nausea and vomiting in cancer patients
Cancer patients who undergo chemotherapy may develop nausea and vomiting as a side effect of their treatment. A 2015 analysis of three studies involving cancer patients undergoing chemotherapy found that nausea and vomiting completely stopped in 47 percent of patients using cannabinoids (THC or CBD), while the symptoms completely stopped in only about 20 percent of those who took a placebo. Another study, of 15 cancer patients who both took THC orally and smoked marijuana, found that most patients experienced reduced nausea and vomiting, compared to when they didn’t receive these drugs.
Another study, of 600 cancer patients, found that the compound nabilone (a synthetic form of THC) was better at preventing nausea and vomiting than were several existing anti-nausea medications. However, more studies are needed to determine whether smoking marijuana works better than newer types of anti-nausea medications for this purpose, a 2016 review said.
Pain in patients with multiple sclerosis
Marijuana may reduce feelings of burning, tingling or numbness, as well as pain from muscle spasms, in patients with multiple sclerosis (MS), according to a 2014 review study. The study found strong evidence that oral cannabis extract, which is a pill made from CBD, or a combination of THC and CBD, can help with these symptoms, the researchers said. However, not enough studies have been conducted to determine whether smoking marijuana helps with symptoms of MS, the review found.
Chronic pain in patients with cancer
A small study of 36 cancer patients found that 10 milligrams of THC produced pain-relieving effects comparable to those of taking 60 mg of the opiate codeine. Another study of a drug called nabiximols (brand name Sativex), which is a “marijuana mouth spray” that contains both THC and CBD, found that low and medium doses of the spray had better pain-relieving effects than a placebo. This result was found in cancer patients with pain who had not been helped by taking opioid drugs. However, very few studies have looked at the benefits of smoked marijuana for treating pain in cancer patients.
A 2010 study looked at 23 patients who had neuropathic pain (which is pain caused by damage to nerves) after trauma or surgery. The study found that those who smoked marijuana reported they had less pain and slept better than those who were given a placebo. A 2013 study of 39 people found that vaporized cannabis reduced neuropathic pain in patients who had not been helped by other treatments.