After several years of declines, overdose deaths among teens are on the rise, driven mainly by opioids.

Drug overdose deaths among older American teens rose in 2015, after declining for several years, a new federal report finds.

This comes even as overall drug use among this group continues to fall.

The report this month from the Centers for Disease Control and Prevention (CDC) found that between 1999 and 2015, drug overdose death rates for 15- to 19-year-olds more than doubled.

In total, there were 772 drug overdose deaths among older teens in 2015, with two-thirds more deaths among males than females.

Between 2014 and 2015, the overdose death rate for males in this age group rose 15 percent. For women the rate increased 35 percent between 2013 and 2015.

This follows earlier gains. The overdose death rate for males declined between 2007 and 2014 before starting to rise again. In females, the rate plateaued between 2004 and 2013, and then rose again.

The overall number of overdose deaths among teens is small, so data from more years will be needed to see if this marks a new trend.

Over 80 percent of overdose deaths in the age group were unintentional, with the rest due to suicides or homicides involving overdose.

Opioids made up the bulk of deaths for all years, vastly outpacing deaths due to cocaine, benzodiazepines, and psychostimulants with potential for abuse.

The report also saw a spike in recent years in teen overdose deaths due to heroin and synthetic opioids, such as fentanyl.

Overdose deaths due to non-methadone, semi-synthetic opioids — such as the prescription pain medications oxycodone and hydrocodone — have declined since 2010.

Dr. Steven Matson, chief of adolescent medicine at Nationwide Children’s Hospital in Columbus, Ohio, said that the CDC report fits with the larger opioid trend.

“Originally it was a lot more prescription drugs that were being snorted, and people were overdosing with regular things like Percocet and OxyContin,” Matson told Healthline. “But now more people are transitioning to heroin — and unknowingly fentanyl — which is obviously a lot more deadly.”

Matson said that at Nationwide Children’s Hospital’s substance abuse program, most of the teens they see have been abusing heroin.

The CDC findings also mirror a trend for all ages in which heroin overtook prescription opioids in 2015 as the leading cause of opioid overdose among all age groups.

While the CDC report focuses on opioid deaths, teens often mix opioids with other substances, which can be particularly deadly.

The annual Monitoring the Future survey for the years 2002-2006 found that 7 out of 10 twelfth graders who used prescription opioids for non-medical reasons combined it with another drug.

More than half mixed opioid pills with marijuana or alcohol. A smaller number of teens mixed them with cocaine, tranquilizers, or amphetamines.

Although heroin is the leading cause of opioid overdose deaths in teens, prescription opioids are still a problem.

“Teens that we treat at Newport Academy for opioid addiction are most likely those who were prescribed a prescription medication by their physician for an opioid for an injury, which is often sports-related,” said Barbara Nosal, PhD, a licensed therapist with Newport Academy.

The rise of prescription opioid addiction among teens — and other age groups — has challenged notions about who is at high risk for substance abuse.

Even a person taking opioids exactly as prescribed by their physician has an increased risk of long-term opioid use after just five days — and one month — of therapy, according to another CDC report.

A 2015 study in the journal Pediatrics also found that teens who are prescribed opioids in high school are 33 percent more likely to misuse any opioid between ages 19 and 23.

Teens may be particularly sensitive to the addictive potential of prescription opioids — simply because of their “nothing will harm me” attitude.

“Unlike adults, teens don’t often consider whether the prescription medication they’re taking might be addicting,” said Nosal. “So teens are less likely to take a medication as prescribed or ‘as needed’ for pain. Their tendency is to take more medication more often than prescribed.”

So if teens are given a 30-day supply of pills for pain, they may take the entire bottle, whether they need it or not. An adult, on the other hand, may switch to an over-the-counter non-opioid pain medication.

Teens who develop an opioid addiction after taking prescription opioid pills — whether prescribed by their doctor or picked up at a party — may eventually turn to heroin.

“Ultimately, we start seeing teens going to the less expensive alternative, heroin,” said Nosal, “because they can no longer afford to buy the pills that they were previously taking.”

The high price of prescription opioids on the street may be a sign that efforts to “crack down” on the diversion of pills are working.

Several states have passed laws limiting how many opioid pills doctors can prescribe at a time. And Prescription Drug Monitoring Programs (PDMPs) allow doctors to check a patient’s prescription history for signs of opioid abuse.

Although some teens begin with prescription opioids, others reach heroin after years of experimenting with other drugs.

“If we look at the people that we’re seeing [in our program] for heroin-use disorder,” said Matson, “most of them started with cigarettes at 10, and alcohol and weed at 12, and then continued to seek out bigger highs, and then got onto pills and ultimately transitioned to heroin.”

Not every teen who uses marijuana will go onto “harder” substances like heroin. But some research suggests that smoking pot is likely to precede the use of — and addiction to — other legal and illegal drugs.

Addiction, though, is a complex mix of biology and environment, which scientists don’t fully understand.

Still, Matson is concerned that legalization of marijuana “is going to make weed more accessible to younger people, and that’s just going to put them at risk.”

He advocates deterring teens from using drugs for as long as possible — giving their brains more time to fully develop.

“As a pediatrician, it would be nice to try to stop the transition of substance use earlier, at the point of alcohol and weed,” said Matson, “before teens get onto the opioids.”

There are signs that efforts to reduce drug use among teens are working.

The annual Monitoring the Future survey for 2016 found that overall, past-year drug use — other than marijuana — among teens is at its lowest point in decades.

Among 12th graders, past-year misuse of prescription opioids has declined over the past five years. Heroin use among 10th- and 12th-grade students remains very low.

Use of marijuana among 10th graders has also declined over the past five years, while holding steady for 12th graders.

For teens who end up with an addiction to opioids or other substances, there are treatment programs that can help — although finding one that focuses on teens can be difficult in some parts of the country.

“It’s really hard to find [addiction specialists] that will see a 14- or 15-year-old, because the system is still pretty much driven by 18 and older,” said Matson.

Matson also warned that there are many “scam” treatment centers trying to cash in on the addiction crisis in the United States. He said pediatricians can help parents choose the best treatment facility for their child.

Addiction treatment for teens is not just about getting them off the drugs or dealing with other destructive behaviors.

Some teens start or continue using drugs — especially ones as strong as opioids — to avoid uncomfortable feelings.

At Newport Academy, the health professionals also work on underlying causes that contribute to substance use in the first place.

“What’s really beneath this behavior? It’s a manifestation of something,” said Nosal. “Teens are externalizing something — their low self-esteem or self-worth — but in a really negative way, which puts them at a high risk of substance use.”