It was roughly 20 years ago, in 1996, that California became the first state to legalize medical marijuana. In the time since, dozens of other states have followed suit, while four have gone even further and legalized cannabis for recreational use.

Teenager Smoking MarijuanaCommon wisdom says the liberalizing of these drug policies should lead more teenagers to use marijuana. Not for the first time, a new study shows that simply isn’t true.

The report, published in the journal Drug and Alcohol Dependence, concluded that cannabis use by American high school students hasn’t risen in the last two decades. In fact, the numbers have dropped – a lot.

Marijuana is currently legal in four states: Colorado, Oregon, Alaska, and Washington, as well as the District of Columbia. Another 30-plus states allow some form of medical cannabis. But the drug remains entirely illegal under federal law.

Critics have been proved wrong

Critics of legalization have long protested that reform would make the drug more widely available, which in turn would lead more kids to use it. In fact, the opposite has happened.

The new study examined information from the Youth Risk Behavior Study prepared by the Centers for Disease Control and Prevention. The authors found that 47 percent of youths admitted to smoking cannabis in 1999. Fourteen years later, just 40 percent said the same.

Previous studies have also demonstrated that legalization doesn’t lead to increased teen use. Even as youth attitudes toward the drug have improved dramatically, relatively few teens actually use it.

The study found they still use it more than any other illegal drug, which is no surprise, as marijuana is the most popular illicit drug among adults too. Very few students admitted to trying hard drugs; just 3 percent said they had ever used methamphetamine, a drop of 6 percentage points since 1999.

General drug use on the decline

Marijuana LeavesAuthors of the study, including Renee M. Johnson, assistant professor in the Department of Mental Health at Johns Hopkins University Bloomberg School of Public Health, noted that most teen drug use is on the decline, despite dire warnings from the drug war crowd. Johnson said his team studied teenage use of a variety of substances.

“Interestingly, we found that use of other drugs, including alcohol, cigarettes, hallucinogens, ecstasy, meth, and cocaine, also decreased over the time period,” Johnson said.

Lifetime cigarette use, for example, declined from 70 percent in 1999 to just 41 percent in 2013. Alcohol use dropped from 81 percent in 1999 to only 66 percent in 2013.

Johnson and his fellow researchers also learned that a one-time gender gap in marijuana use has closed. In 1999, 51 percent of boys had smoked cannabis compared to just 43 percent of girls. By 2013, the numbers had dropped to 42 percent for boys and 39 percent for girls.

state marijuana laws