Marijuana use is not on the rise.
At least, that's the gist of the National Survey on Drug Use and Health done every year by the U.S. Department of Health and Human Services. In 2008 -- the most recent data available -- 6.1 percent of Americans 12 and older admitted using marijuana in the previous month.
In absolute terms, that number is probably low; after all, this survey asks people to admit to using illegal drugs. But the real significance of the number is that it's steady -- it's been hovering right around 6 percent since 2002. Drug researchers say the real percentage may be higher, but it's probably holding steady, too.
Marijuana Use: 2002-2008
This graph shows the percent of those age 12 or older who said they used marijuana in the past month.
And yet, during those same years, marijuana has been edging toward legitimacy. States with medical marijuana laws have made it possible for thousands of people to buy pot over the counter, in actual stores. Some police departments have started de-emphasizing marijuana arrests.
Critics of liberalization believe this inevitably leads to greater consumption.
"It's axiomatic," says John Lovell, a lobbyist for California police chiefs. He's also helping to organize the campaign against an initiative in California to make marijuana legal for adults.
"Anytime you take a product -- any product -- from a less convenient sales forum to a more convenient sales forum, use increases," Lovell says.
But cities where marijuana have been liberalized have not seen a spike in consumption, so far. In 2003, voters in Seattle made marijuana the "lowest law enforcement priority" for city police. Researchers tracked the results. Caleb Banta-Green studies drug use trends at the University of Washington's Alcohol and Drug Abuse Institute. He says self-reported consumption and pot-related emergency room visits remained flat, before, during and after the initiative went into effect.
Banta-Green says he gets similar reports from drug researchers in other cities.
"I'm not hearing stories on a regular basis that, 'There was liberalization in marijuana policies, and soon afterwards, usage rates increased dramatically,' " he says.
At the same time, says Banta-Green, places like Seattle already had high rates of pot consumption before enforcement was relaxed, so it's not surprising that there was no big increase.
And opponents of liberalization say even if overall consumption stays flat, looser enforcement may increase pot smoking among minors.
They point to places such as California's Bay Area, where medical marijuana is commonplace and enforcement is lax. Teenagers rarely have trouble finding pot. Some get it from dispensaries; far more just buy it from a friend or classmate.
"I could call 10 people right now and they'd all have a drug dealer," says one teenager, who declined to give his name.
As in Seattle, Berkeley voters made pot arrests the lowest priority for police, but they did it nearly 25 years earlier. Still, Berkeley school officials were shocked last year when they saw results from the statewide "California Healthy Kids" survey of student drug use. Sixty-three percent of the district's 11th graders reported smoking pot in their lifetime -- 20 points higher than the state average.
Another high school boy, a self-described "stoner" who also spoke on the condition his name not be used, isn't surprised by that number.
"You can definitely get it anywhere. And that leads kids to smoke more, and that leads kids to buy more, and that leads other dealers to sell more and cannabis clubs to sell more. So it's definitely growing a lot," he says.
But even though the rate of teenage pot smoking in Berkeley is high, it's also been stable. The survey shows it, as does the experience of high school teacher Mark Harringer.
"I haven't seen a marked increase or decrease either way," Harringer says. He thinks kids just get the impression consumption is growing because, as they grow older, they're more likely to encounter friends using drugs.
"I've even asked kids before as well, 'What percentage of your class do you think uses marijuana or drinks alcohol or smokes cigarettes?' " Harringer says. "And more often than not, they inflate the number almost triple than what the actual percentage is."
Some Statistics May Be Disturbing
But even if overall consumption is stable, other numbers are increasing. At the University of Washington, Banta-Green says the Seattle area has seen an increase in the number of people getting treatment for pot addiction. That is, of the people entering treatment, an increasing percentage cite marijuana as their primary addiction. Similar increases are being seen in San Francisco and Los Angeles, where marijuana dispensaries have boomed in the past couple of years.
It's not clear what the increase means; Banta-Green says it might have something to do with more probation violators being sent to treatment instead of jail, when they test positive for pot.
When it comes to illegal drugs, he says, it's just hard to get reliable measurements of overall consumption -- even in areas where the drug has been liberalized.
But it's not impossible. Banta-Green has been part of a project that measures the traces of illegal drugs in sewer water. He's been analyzing the wastewater in 20 cities to get a measure of overall consumption of certain hard drugs. And he'd like to start testing that water for pot, too, if he can get the funding.
This story includes reporting by Sayre Quevedo of Youth Radio, which trains young journalists