It's late Saturday night. A group of friends are gathered in a Linden Hills kitchen. The 17-year-olds order in from Pizza Lucé, go out to the screened porch and light up. It isn't tobacco.

They use a bubbler, a pipe with a water chamber, which is supposed to make the effects of the marijuana last longer.

Ann prefers to do it this way, smoking pot at home, even though her parents don't exactly approve.

"I would rather have my family find me than some random stranger," she said. "I know my family's forgiving."

Ann (who asked that only her middle name be used) and her friends are not isolated cases. A May 2012 study by the Partnership at found that 27 percent of teenagers nationwide said they used marijuana within the previous month, a 42 percent increase from 2008. Nine percent of teens said they used marijuana 20 or more times the previous month, up 80 percent.

This sharp rise comes at a time when tobacco use among teens is waning. "It's consistent with the whole social disapproval of cigarette smoking," said Sean Clarkin, director of programs at the Partnership, formerly the Partnership for Drug-Free America, which works to support families of children who use drugs. "Smoking has become less cool because people know it can hurt other individuals. But marijuana is more normalized. It's just part of many kids' everyday existence."

Weighing health risks

Parents -- often former pot smokers themselves -- are sometimes challenged by children who maintain that marijuana is safer and less noxious than tobacco or alcohol, let alone stronger drugs like cocaine, heroin or methamphetamine.

Experts say marijuana's increasingly benign reputation is undeserved.

Some teenagers, and even some parents, don't want to talk about the risks of respiratory and brain damage, never mind addiction, said Dr. Joseph Lee, medical director for Hazelden youth services. New research has found IQ reductions among teens who use marijuana 20 or more times a month, he said.

"The issue is not whether marijuana is better or worse than cigarettes or alcohol or some other drug,'' he said. "That's a little like asking, 'Which cancer is the best one to have?' How about choosing no cancer?"

"The thing is, almost no kid who's using thinks it's a problem," Lee added.

Cancer link debated

The relationship between marijuana smoking and lung cancer is hotly debated, with opinions running the gamut from claims of a direct link to arguments that marijuana use actually can retard lung cancer.

"Marijuana smoke contains 50 to 70 percent more carcinogenic hydrocarbons than tobacco smoke," according to the National Institute on Drug Abuse website. "Marijuana users usually inhale more deeply and hold their breath longer than tobacco smokers do, which further increases the lungs' exposure to carcinogenic smoke."

On the other hand, Harvard University researchers found that in mice with lung cancer, exposure to the main active ingredient in pot -- delta-tetrahydrocannabinol, commonly referred to as THC -- reduced tumor growth by 50 percent. Researchers at UCLA concluded that research about marijuana use and cancer in humans was inconsistent at this point.

That doesn't mean there are no lung-related health risks. Yale University researchers compared data from several studies on the effects of marijuana and tobacco smoking, and discovered an "increased risk of many of the same respiratory problems," including shortness of breath, wheezing and chronic bronchitis.

Addiction risks

When William Moyers, vice president of community affairs at Hazelden, talks to teenagers about marijuana -- including his own three children -- "I don't tell them never to use, although I do point out that it's illegal. I tell them to look at me -- look at their families -- to see what can happen."

Son of famed journalist Bill Moyers, he first toked up at about age 15, mainly on weekends. At 18 he began using alcohol legally. Then came more experimentation and he became addicted to crack cocaine.

"I'm 53 and I've been sober for 18 years," Moyers said. "Nobody starts out to be an addict -- and most people who use marijuana or alcohol won't become dependent. But some will."

Because both of their parents were dependent on drugs, his children know they are four to seven times more likely than other kids to move from drug use to addiction, he said.

Lee recommends that concerned parents first seek counsel from their children's physicians, who can screen the kids for problems and may recommend therapists or treatment.

Most friends are users

Ann smokes cigarettes on occasion, but finds a stigma attached to them that she doesn't find with pot. Her boyfriend once criticized her for tasting like cigarettes. "I think more people are like, 'Ew, cigarettes, that's dirty.' With pot, they're not going to be like, 'You're killing your body.'"

Ann estimated that 80 percent of her friends smoke marijuana. She mostly smokes on weekends, and only if she doesn't have anything else to do. She doesn't drive when she's high. She never smokes alone.

"If you're doing it by yourself, it's more of a vice," she said. "There's a difference between being addicted significantly to something and being comfortable using something all the time."

She doesn't see herself becoming a drain on society: She's studying engineering at the University of Minnesota this fall.

But the culture in which Ann gets high is vastly different from the culture of a decade ago, said Victor, 25, a recovering addict who asked that his last name not be used. When he was growing up in Iowa, marijuana "was one of those things that the bad kids, the kids that don't have their lives together, were doing."

Victor stayed away from the drug until college, when he got hooked. At the height of his addiction, he was smoking half an ounce every day. He dropped out of college, started dealing and wound up homeless.

Almost four years ago, Victor checked himself into Hazelden and has been sober since. Now living in St. Paul, he has gotten his life back together, but fears that if marijuana had been as popular among teens then as it is today, he might not have been able to recover.

"I would have definitely fallen into the same pattern that I did -- it just would have been earlier in life," said Victor. "I don't know if I would have graduated high school, had it been trendy."

Staff writer Jeff Strickler contributed to this report.