Teen alcohol and drug use -- including marijuana use -- was down across the board in 2014.

That's the big take-home from the 2014 Monitoring the Future study by the University of Michigan and the National Institutes on Drug Abuse, which was released Tuesday morning. The MTF is an annual survey of 40,000 8th-graders, 10th-graders and 12th-graders. It's notable both for its size and for the fact that it was conducted this past spring, in the midst of a nationwide conversation about drug reform in the run-up to the midterm elections. Here's what the survey found:

Marijuana use? Down. Alcohol use? Way down. Cigarettes? Waaay down. Fewer than 15 percent of 12th-graders reported using cigarettes any time in the past month, down from well over 35 percent in the late 1990s. Monthly alcohol use dropped from nearly 55 percent of 12th-graders in 1992 to less than 40 percent in 2014. Even weed, which has been on a flatter trajectory since the 1990s than the other substances, is down year over year.

These numbers comport with findings earlier this year from the National Survey on Drug Use and Health, the government's other major substance use barometer.

Even better news is that frequent, daily use -- which experts agree is the most harmful to developing young minds -- is also down considerably. Cigarettes posted the sharpest drop in daily use, falling from nearly 25 percent of 12th graders in 1997 to about 7 percent in 2014. Frequent alcohol use has declined, although less dramatically. Frequent marijuana use had been on a slight rise for roughly the second half of the 2000s, but since about 2011 it's either held steady or fallen.

"Both alcohol and cigarette use in 2014 are at their lowest points since the study began in 1975," the study's authors conclude in a press release. The National Institutes of Drug Abuse agrees: “with marijuana use appearing to level off, and rates of many other drugs decreasing, it is possible that prevention efforts are having an effect,” said director Nora D. Volkow in a release.

The marijuana findings are particularly noteworthy given that Colorado and Washington state implemented full-scale retail marijuana markets this year, and Oregon, Alaska and Washington, D.C., voters opted to do the same. A central tenet of legalization opponents, from present-day prohibitionists like Andy Harris all the way back to Richard Nixon, has been that loosening restrictions on marijuana will "send the wrong" message to youngsters and lead to an explosion in teen use.

Harris sums up the mindset best in a recent appearance at the Heritage Foundation"Relaxing [marijuana] laws clearly leads to more teenage drug use. It should be intuitively obvious to everyone that if you legalize marijuana for adults, more children will use marijuana because the message that it's dangerous will be blunted."

While it's a politically potent message -- nobody wants to see more kids doing drugs -- there's a substantial body of research showing that teen pot use hasn't risen in the states that have legalized medical marijuana. In 2014, a year when marijuana was all over the news and national attitudes toward the drug are relaxing, teen use actually trended downward.

Or, look at it from the other side: In the early 1990s the federal drug war was in full swing. But teen marijuana use spiked sharply during that period. It didn't start falling until the late '90s, when the first states began implementing medical marijuana laws.

This isn't to say that repealing harsh marijuana laws will necessarily cause teen use to trend downward. But it does at the very least illustrate that it's impossible to draw a straight line from "relaxing marijuana laws" to "increased teen use," as Harris and other prohibition enthusiasts do. And there are compelling arguments to be made that taking the marijuana trade off the black market, and letting government and law enforcement agencies, rather than criminals, control the marijuana market, will lead to better overall drug use outcomes among teens.

Regardless of where you come down on the drug war, there's something in here for everyone to be cheerful about. The kids, broadly speaking, are alright.