The average age at which American teens are first using drugs, including tobacco and alcohol, has been increasing, according to a study published Monday in the journal JAMA Pediatrics.

Significantly fewer young people are using drugs before their 16th birthday than just a decade ago, the study found.

“This is great news, because delaying drug use prevents early exposure, which is associated with a variety of negative health consequences, including increased risk of drug use disorder and long-term impairments such as depression, neurocognitive deficits, involvement in risky behaviors, and sexually transmitted diseases,” says Karl Alcover, the study’s lead author and a postdoctoral research associate at Washington State University, in a released statement.

The findings are yet another indication of an overall downward trend in risky behavior among American adolescents over the past two decades. Research has found, for example, that sexual activity among high school students has fallen in recent years, and the birth rate among teens has declined dramatically.

A government report published in 2018 found a decrease in the use of some drugs, such as tobacco and marijuana, among young people aged 12 to 17, but an increase among those aged 18 to 25. That finding suggested an overall rise in the average age at which young people were starting to use drugs.

To see if that were true, Alcover and his colleagues decided to look more closely at the available age-related data for 18 separate drugs.

Key findings

The data came from more than 338,000 young people aged 12 to 21 who took part between 2004 and 2017 in the National Survey on Drug Use and Health, an annual (and anonymous) survey run by the U.S. Department of Health and Human Services.

The survey’s questions included ones that asked the young people whether they had used alcohol, tobacco or other drugs, and, if so, at what age they had started doing so. More than 84,000 of the respondents said they had tried at least one of the drugs.

The starting age for six drugs — crack cocaine, methamphetamines, opioids, PCP, sedatives and tranquilizers — did not change either up or down in any statistically significant way during the period of the study.  But for the other 12 drugs — alcohol, cigarettes, cigars, smokeless tobacco, marijuana, cocaine, ecstasy, hallucinogens, heroin, inhalants and LSD — the average age at which the young people reported first using them increased.

The upward trend in starting age was relatively consistent from year to year for all but two drugs: alcohol and LSD. The average age that young people began drinking alcohol was about 16 years in 2004. By 2017, it had risen to about 17 years — “a full year after the minimum age for an unrestricted driver’s license in the United States,” Alcover and his co-authors point out.

But that rise in starting age continued only until 2014. Since then, it has leveled off.

A similar pattern has occurred with the average age at which young people are first using LSD. It rose from just under 17 years to just under 18 years — where it has also stalled.

That may mean, Alcover and his colleagues write, “that trends toward later ages at initiation may have already ended.”

Among the 18 drugs, inhalants had the earliest average age of first use: 15.4 years. Both cocaine and crack cocaine had the latest average age of first use: 18 years.

Finding out why

The study relied on self-reported data, which can be unreliable. In addition, the survey did not include e-cigarette use, which is on the rise among teenagers.

Still, the findings are encouraging. The next step, says Alcover, is to figure out exactly what is driving an increasing proportion of young people to hold off from using drugs.

“These promising trends may serve as early evidence that prevention strategies — especially those focused on teens and young adults — are working,” he says.

FMI: You’ll find the study on JAMA Pediatrics’ website, although the full paper is behind a paywall.