Teenagers are smoking less tobacco and drinking less alcohol, but they're using more marijuana, according to a new report by the National Institute of Drug Abuse.

More than 60 percent of high school seniors do not view marijuana use as harmful and 23 percent report smoking pot in the past month, said the report released Wednesday.

NIDA director Dr. Nora Volkow blames the acceptance and use figures on adults and the media message following marijuana legalization in Colorado and Washington State.

"These changes in perception come because of legalization of marijuana as medicine," Dr. Volkow said. "Teens use it because they think marijuana is less harmful, since it cannot be as harmful if it has a medical purpose."

Teen cigarette smoking continues to decline, falling to 10 percent today from 25 percent in 1993, according to the report. Alcohol use peaked in 1997, when 52 percent of high school seniors used alcohol monthly, that is now down to 39 percent.

But experts fear marijuana will continue on the upswing as more states adopt laws allowing medical marijuana, supply grows and prices decline. That is bad news for younger teens who light up.

"When you smoke pot, it interferes with the way you learn and memorize" says Volkow. "If you regularly consume pot, it affects your scholastic achievement."

In those states where medical marijuana is legal, 34 percent of teens get their pot not from a drug dealer, but someone who buys their marijuana with a prescription. This contradicts the claim by many medical marijuana proponents that state regulations would keep pot out of the hands of kids. In fact, among states reporting the highest teen marijuana use - 19 of the top 20 already legalized medical marijuana.

"We know that for most of those, marijuana is not from prescription given to them but prescription to someone else, whether that is adult relative or friends is not clear," says Volkow.

But even in states where reefer remains illegal, the DEA says 88 percent of cities report pot is widely available. The agency itself is eradicating 77 percent less pot than just three years ago, suggesting it too is not enforcing pot laws with the same vigor as in decades past.

With less eradication and less enforcement, domestic production is up, forcing the Mexican cartels to ship more of their lesser quality, lower priced pot in bulk to replace revenues lost to domestic competition. Seizures in the Tucson Border Patrol Sector are up 40 percent over last year. Recently, agents seized 10 tons of pot at a checkpoint in Nogales, while on Monday an ultra-light aircraft dumped a large marijuana load just south of Tucson.

Said one agent who asked to remain anonymous, "We are seeing a ton of pot right now."