How healthy - or dangerous - is marijuana use?


c.2010 San Francisco Chronicle

Proponents of legalizing marijuana say it's a fun-filled wonder weed that relieves all manner of pain and may even cure cancer. Federal researchers and other pot foes say it's the devil's drug, ruining people's lungs and turning stoned drivers into wheeled killers.

So, which side is blowing smoke? Is pot healthy for you, or as damaging as, say, tobacco?

With only sporadic research possible because marijuana is illegal under federal law, the gray area between the two sides is a yawning gulf -- leaving foes and proponents of cannabis plenty of ground to make claims.

The question of marijuana's health effects becomes more urgent as the November election draws nearer and California voters consider whether to pass Proposition 19, which would legalize recreational marijuana use. With a recent Rand Corp. study finding that the number of pot smokers would rise substantially if the measure wins, each side in the health debate has all the more reason to convince people that the drug is either damaging or harmless.

Taking lead for the devil weed portrayal, the National Institute on Drug Abuse -- the main federal resource for information about harm caused by narcotics -- maintains that cannabis contains as much as 70 percent more carcinogenic hydrocarbons than tobacco, jacks up a user's heart rate by as much as 100 percent and can worsen anxiety and depression.

The institute also says research by Harvard University and other organizations shows that marijuana use is responsible for as many as 14 percent of car accidents involving injuries, that people who become addicted mostly say it's degraded their lives, and that inhaling pot smoke damages lungs.

"Some people think marijuana is just something they may have used when they were younger, and have different perceptions about its harmfulness, but we want people to know that there are risks out there," said Susan Weiss, a policy chief for the drug abuse institute. "It's not just harmless, especially for young people."

This all sounds like the 1936 dope-scare "Reefer Madness" flick to cannabis fans.

Pointing to studies conducted by Kaiser Permanente and others, pot supporters say the weed is safer than tobacco because it doesn't cause cancer and is less addictive, when used correctly it relieves rather than exacerbates anxiety and depression, and it even shows the promise of curing cancer.

Rather than demonize marijuana as damaging to one's health, advocates say, it should be as celebrated as a drug that has brought relief to hundreds of thousands since voters approved the use of medicinal marijuana in California in 1996.

Not a single death has been traced directly to pot use, they say. And as far as claims that stoned drivers get so disoriented they cause car crashes -- pro-weed researchers even have a study that disputes that.

The National Institute on Drug Abuse "looks for the negative stuff on purpose, and disregards anything positive about cannabis," said Fred Gardner, managing editor of O'Shaughnessy's, a leading pro-cannabis research magazine. "This medicine actually has great benefits, and more people need to know that."

With marijuana illegal at the federal level, research will remain sparse even if the California measure passes. Study grants are small and limited even on a local level, the state is conducting no major research, and federal certifications from agencies such as the Food and Drug Administration, which could authoritatively legitimize claims of usefulness or harm, are impossible for an illegal substance.

"There are some issues in doing research because it's illegal," Weiss said. "It can be tricky territory."

That's not stopping her and other federal agencies from sounding the alarm.

The chief detrimental aspects of marijuana cited by the national institute and the U.S. Drug Enforcement Administration are the risks of addiction, the doping-down effect heavy pot use has on a person's physical and mental well-being, and the impairment it causes in the brain that can lead to bad driving.

A 2006 paper issued by the DEA, based on research by the national Substance Abuse and Mental Health Services Administration and other agencies, contended that 14.6 million people had smoked or otherwise ingested marijuana over a recent one-month period, making it the most commonly used illegal drug in the nation. It also said more people ages 12 to 17 entered rehabilitation treatment programs for marijuana dependence than for alcohol and all illegal drugs combined.

Weiss cites a 1994 study by researchers from Johns Hopkins University and the University of Michigan that found about 9 percent of pot smokers become addicted. Although less than the 30 percent figure for cigarette smokers, that's no cause for celebration, she said.

As for the self-esteem of those who have toked up heavily: A 2003 Harvard medical survey showed that 90 percent of those queried said significant marijuana use had a negative effect on their cognition and memory, and more than half said it hurt their careers, social lives, and physical and mental health.

"What we seem to find is that using marijuana, like alcohol, can make you feel good at first, but after you smoke it for a while it can turn against you," Weiss said.

Driving while under the influence is another deal-stopper for federal officials regarding pot legalization.

Testing for recent marijuana use mostly relies on blood tests, because urine and breath tests aren't as accurate as they are for alcohol. But Weiss's agency says statistics from several localities in the United States, France and Australia over the past 20 years show that, in addition to playing a part in up to 14 percent of injury wrecks, marijuana is a factor in 2.5 percent of fatal accidents.

"It causes increased weaving and slower reaction time, much like having drunk beer," Weiss said.

Marijuana advocates say doing anything to an extreme can be harmful. But they cite a study on pot and booze in car crashes by Australian doctors Gregory Chesher and Marie Longo that concluded, "At the present time, the evidence to suggest an involvement of cannabis in road crashes is scientifically unproven."

The yin-yang contentions also ring loud on anxiety and depression.

Studies cited by Weiss' agency contend that marijuana users are more susceptible to those problems. On the other side are medical cannabis dispensers who cite studies such as one published in 2004 in the Journal of Acquired Immune Deficiency Syndromes that said the effects of marijuana include "relief of anxiety and/or depression."

One thing both sides agree on is that sucking smoke into the lungs is not good.

"We still don't know if marijuana causes cancer, but breathing in its smoke causes coughing and wheezing and worsens asthma symptoms, like tobacco," Weiss said.

Gardner, the marijuana-research magazine editor, concurs that smoke damage to lung cells is nasty. "If you saw the photos, you'd never want to take another puff again," he said.

But he cites studies at UCLA in 2005 and Kaiser Permanente in 1997 -- which, combined, examined the records of more than 65,000 patients -- that contended there was no evidence linking marijuana to cancer. And there are always other ways of ingesting the weed, such as eating it, that don't involve smoke, Gardner pointed out.

In fact, he and Steve DeAngelo, whose Harborside Health Center in Oakland is the biggest cannabis dispensary in the country, say that rather than causing cancer, recent studies show that marijuana's CBD component -- which unlike the plant's other main component, THC, doesn't produce euphoria -- has shown promise as a cancer-inhibiting agent.

"Nature gives us everything for a reason," DeAngelo said. "It doesn't make any mistakes. And with cannabis it gave us the single most valuable plant on the planet -- no plant can cure so many illnesses and relieve so many symptoms. People need to know that."

Weiss agrees that the research showing anti-cancer potential is "fascinating," but she doesn't bite on the "most valuable" bit.

"We don't have as good data as we have for alcohol, but the evidence is already clear," she said. "Marijuana is not good for you."

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