Marijuana less cancerous than tobacco

October 16, 2005

Steve Mitchell, UPI

Marijuana is less carcinogenic than tobacco smoke and may even have some anti-cancer properties, new research suggests.

Robert Melamede, chair of biology at the University of Colorado in Boulder, reviewed studies of the illicit drug and published his findings in the Oct. 17 issue of Harm Reduction Journal.

Melamede's conclusion is certain to factor in the medical-marijuana debate, because the cancer-causing potential of the drug is one of the reasons often cited by those who oppose legalizing it for medicinal uses. He said he was motivated to investigate the issue because the Drug Enforcement Administration has made the argument that marijuana has four times the amount of tar contained in tobacco smoke, so it is potentially carcinogenic.

"I said, 'Let's see what's true because the government doesn't have a very good record on telling the truth about cannabis,'" Melamede, who classifies himself as a medical-marijuana advocate, told United Press International.

He said the studies indicated although marijuana smoke does contain carcinogens, it does not appear to induce cancer because of its unique pharmacological properties. Lung cancer, for example, is caused by a combination of carcinogens in conjunction with nicotine found in tobacco smoke.

"It's the nicotine that's really the cancer-promoting agent," he explained. "That's absent in marijuana smoke so you don't have that enhancing factor."

Studies to date have not linked marijuana smoking with the lung, colon, rectal and other cancers associated with tobacco smoking, Melamede said. In addition, other studies have indicated compounds found in cannabis might even kill certain cancers, including lung, breast, prostate and skin, as well as leukemia and lymphoma, and a type of brain cancer called glioma.

"That's not to say smoking marijuana is good," Melamede noted. It is a lung irritant and can cause respiratory problems, such as coughing. Also, it is full of carcinogens, so "even if it's not causing cancer, it's having negative effects," he said.

One alternative would be to use a vaporizer, rather than smoking, to deliver the marijuana.

"It should be noted that with the development of vaporizers, that use the respiratory route for the delivery of carcinogen-free cannabis vapors, the carcinogenic potential of smoked cannabis has been largely eliminated," Melamede wrote in the journal.

At least 10 states, including California and Colorado, have moved in the direction of allowing patients to use marijuana with a doctor's approval. The DEA has attempted to enforce a federal ban on the drug, however, and has arrested patients using it. This policy has discouraged doctors from recommending it for medical use.

The U.S. Supreme Court ruled last June that the federal prohibition supersedes state laws and the DEA can arrest patients who use the drug.

Karen Tandy, the DEA's administrator, wrote in an article titled, "Marijuana: The Myths Are Killing Us," which appeared in the March issue of Police Chief magazine, that the drug is hazardous to health and does not help patients.

"The scientific and medical communities have determined that smoked marijuana is a health danger, not a cure," Tandy wrote in the article, which also appears on the DEA Web site. "There is no medical evidence that smoking marijuana helps patients."

Tandy did not claim marijuana caused cancer, but she implied it by saying, "marijuana smoke ... contains 50 to 70 percent more carcinogenic hydrocarbons than tobacco smoke and produces high levels of an enzyme that converts certain hydrocarbons into malignant cells."

She also said marijuana can cause anxiety and depression, particularly in teens. However, a study released last week from Canadian researchers found a synthesized version of a marijuana compound actually promotes development of new brain cells in rats, and this in turn was accompanied by a reduction in anxiety and depression.

Other risks of marijuana cited by Tandy included impaired cognitive function, such as short-term problems with perception and memory.

Allen St. Pierre, executive director of the National Organization for the Reform of Marijuana Laws, told UPI that Tandy's assertions "run up against the known science," which indicate the toxicity of the drug is minimal.

"While not harmless, marijuana comes very close to being benign when compared to other prescription drugs," St. Pierre said.

He noted that Dr. Tod Mikuriya, a psychiatrist in El Cerrito, Calif., had conducted a study with medical-marijuana patients and did not find evidence they developed cognitive impairments, paranoia, anxiety or other mental problems after they began using the drug.

"The government has insisted there are no pros and there are only cons of marijuana, but this is totally lacking in science and totally lacking in any realistic credibility," Melamede said.

He predicted medical marijuana ultimately will be permitted in the United States.

"It's unavoidable that it will eventually triumph because it works," he said. "The government is lying and it will eventually win out in the end. It's just a matter of how many people have to suffer between now and then."

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