Amid an opioid epidemic, the rise of deadly synthetic drugs and the widening legalisation of marijuana, a curious bright spot has emerged in the youth drug culture: US teenagers are growing less likely to try or regularly use drugs, including alcohol.

With minor fits and starts, the trend has been building for a decade, with no clear understanding as to why. Some experts theorise that falling cigarette-smoking rates are cutting into a key gateway to drugs, or that anti-drug education campaigns, long a largely failed enterprise, have finally taken hold.

But researchers are starting to ponder an intriguing question: Are teenagers using drugs less in part because they are constantly stimulated and entertained by their computers and phones?

The possibility is worth exploring, they say, because use of smartphones and tablets has exploded over the same period that drug use has declined. This correlation does not mean that one phenomenon is causing the other, but scientists say interactive media appears to play to similar impulses as drug experimentation, including sensation-seeking and the desire for independence.

Or it might be that gadgets simply absorb a lot of time that could be used for other pursuits, including partying.

Nora Volkow, director of the National Institute on Drug Abuse, says she plans to begin research on the topic in the next few months, and will convene a group of scholars in April to discuss it. The possibility that smartphones were contributing to a decline in drug use by teenagers, Volkow said, was the first question she asked when she saw the agency's most recent survey results. The survey, "Monitoring the Future," an annual government-funded report measuring drug use by teenagers, found that past-year use of illicit drugs other than marijuana was at the lowest level in the 40-year history of the project for eighth, 10th and 12th graders.

Use of marijuana is down over the past decade for eighth and 10th graders even as social acceptability is up, the study found. Though marijuana use has risen among 12th graders, the use of cocaine, hallucinogens, Ecstasy and crack are all down, too, while LSD use has remained steady.

Even as heroin use has become an epidemic among adults in some communities, it has fallen among high schoolers over the past decade, the study found.

Those findings are consistent with other studies showing steady declines over the past decade in drug use by teenagers after years of ebbs and flows. Volkow said this period was also notable because declining use patterns were cutting across groups – "boys and girls, public and private school, not driven by one particular demographic," she said.

"Something is going on," Volkow added.

With experts in the field exploring reasons for what they describe as a clear trend, the novel notion that ever-growing phone use may be more than coincidental is gaining some traction.

Explanations aside, researchers unanimously expressed hope that the trends would persist. They noted it was crucial to continue efforts to understand the reasons for the decline, as well as to discourage drug use.

Though smartphones seem ubiquitous in daily life, they are actually so new that researchers are just beginning to understand what the devices may do to the brain. Researchers say phones and social media not only serve a primitive need for connection but can also create powerful feedback loops.

"People are carrying around a portable dopamine pump, and kids have basically been carrying it around for the last 10 years," said David Greenfield, assistant clinical professor of psychiatry at the University of Connecticut School of Medicine and founder of The Center for Internet and Technology Addiction.

Alexandra Elliott, 17, a senior at George Washington High School in San Francisco, said using her phone for social media "really feels good" in a way consistent with a "chemical release". A heavy phone user who smokes marijuana occasionally, Alexandra said she didn't think the two were mutually exclusive.

However, she said, the phone provides a valuable tool for people at parties who don't want to do drugs because "you can sit around and look like you're doing something, even if you're not doing something, like just surfing the web."

"I've done that before," she explained, "with a group sitting around a circle passing a bong or a joint. And I'll sit away from the circle texting someone."

Melanie Clarke, an 18-year-old taking a gap year and working in a Starbucks in Cape Cod, Massachusetts, said she had virtually no interest in drugs. "Personally, I think it is a substitution," Clarke said of her phone, which she said she was rarely without. Clarke also said she thought the habits depended on the person. "When I'm home alone, my first instinct is to go for the phone. Some kids will break out the bowls," referring to a marijuana-smoking device.

"There is very little hard, definitive evidence on the subject," said James Anthony, a professor of epidemiology and biostatistics at Michigan State University and an expert on drug-use behaviour. Still, he said, he has begun wondering about the role of technology on youth drug use: "You'd have to be an idiot not to think about it."

To see declines in drug use, Anthony said, "it would not take much in the way of displacement of adolescent time and experience in the direction of nondrug 'reinforcers' that have become increasingly available."

Smartphones and computers are a growing source of concern, said Eric Elliott, Alexandra's father, who is a psychologist at her school. Elliott, who has counselled young people for 19 years, said he had seen a decrease in drug and alcohol use among students in recent years. He said he was "more likely to have a challenge with a student who has a video game addiction than I am a student who is addicted to drugs; I can't say that for the beginning of my career."

In the case of his own daughter, he worried more about the device than the drugs.

"I see her at this point and time as not being a person who is controlled in any way by smoking pot," he said. But "her phone is something she sleeps with."

New York Times