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The latest update to the annual Monitoring the Future survey of drug use in American youth bears mainly good news, at least if your interest is in reducing drug-related harm: both teen drinking and cigarette smoking are at historic lows; in fact, past-month marijuana use is now more commonly reported by high school seniors than smoking cigarettes. Misuse of prescription medications in teens is stable or declining.

Nineteen percent of high school seniors reported smoking at least one cigarette in the previous month, compared with 23% who reported smoking marijuana.

“That cigarette use has declined to historically low rates is welcome news, given our concerns that declines may have slowed or stalled in recent years,” Dr. Nora Volkow, director of the National Institute on Drug Abuse, said in a statement. “That said, the teen smoking rate is declining much more slowly than in years past, and we are seeing teens consume other tobacco products at high levels. This highlights the urgency of maintaining strong prevention efforts against teen smoking and of targeting other tobacco products.”

Marijuana use has increased: about a quarter of all high school students surveyed reported using marijuana in the previous year, up from about 21% in 2007. Also worryingly, the survey saw a rise in daily use of marijuana by high school seniors, which reached a peak — at 7% — not seen since 1981. The highest rate of daily marijuana use by 12th graders was 11%, in 1978.

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Existing data suggests that smoking marijuana is safer than smoking cigarettes. Research finds that cigarette smoking is ultimately responsible for the deaths of about half of all smokers, mainly due to heart disease and lung cancer. Although a few studies find that marijuana smoking could also lead to cancer, most research does not show increased mortality risk associated with the amount of pot that is typically used — and the risks that are seen are nowhere close to those associated with tobacco smoking. Daily use of marijuana by teens, however, is another story: it poses a high risk of addiction and for problems in school.

Compared to marijuana, alcohol has higher risks for addiction, overdose, violence and related driving while intoxicated. Virtually the only measure by which alcohol use is more benign is in associated legal penalties.

The survey found that teens’ misuse of prescription drugs has also declined, in part, perhaps, because the medications have become harder to get. Misuse of Vicodin, the most widely used prescription pain reliever, was reported by 8% of high school seniors, down 23% to 30% from its peak, depending on the grade level, in the early 2000s.

The survey also found continued declines in cocaine use and the misuse of cough and cold medications.

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But the news is not all good. A stunning 11% of high school seniors reported having used synthetic marijuana — also known as “legal highs” — like K2 or Spice in the past year. Most kids who tried synthetic marijuana also smoked the real stuff. These “herbal” concoctions, which contained lab chemicals that have never been tested in human beings, were widely available online and in convenience stores, until their chemical ingredients were made illegal in March. The drugs have been linked with paranoid reactions, seizures and possibly several deaths, and their long-terms effects are unknown.

“K2 and spice are dangerous drugs that can cause serious harm,” drug czar Gil Kerlikowske said upon releasing the data. “We will continue to work with the public health and safety community to respond to this emerging threat.”

Responding to the research, Jag Davies, publications manager for the Drug Policy Alliance, which supports liberalizing drug policy, wrote: “The decline in cigarette smoking is great news — not just because it’s the most deadly drug but also because it reveals that legal regulation and honest education are more effective than prohibition and criminalization. It’s absurd, though, that the survey doesn’t also include the fiscal, health and human costs of arresting more than 1.6 million Americans each year on drug charges, including more than 750,000 for marijuana possession alone.”

The survey included some 47,000 8th, 10th and 12th graders this year, and contains data going back to 1975. The survey and related data can be found here.

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Maia Szalavitz is a health writer at TIME.com. Find her on Twitter at @maiasz. You can also continue the discussion on TIME Healthland’s Facebook page and on Twitter at @TIMEHealthland.