Drug overdose deaths among U.S. teens edged upward in 2015 after declining for several years, according a new report.

The report, from the Centers for Disease Control and Prevention, looked at drug overdose deaths among Americans ages 15 to 19 over a 16-year period.

The report showed that from 1999 to the mid-2000s, drug overdose deaths in this age group more than doubled, from 1.6 deaths per 100,000 people in 1999 to 4.2 deaths in 2007. This increase coincided with a rise in drug overdose deaths among the U.S. population as a whole, an increase that has been partly attributed to the opioid epidemic.

However, after 2007, drug overdose deaths among teens declined, reaching 3.1 deaths per 100,000 people in 2014, the report said. (The drop was driven by a decrease in drug overdose deaths among males in this age group.)

But in 2015, the most recent year for which data is available, drug overdose deaths among teens increased again, to 3.7 deaths per 100,000 people, a 19 percent increase compared with 2014, the report said. In total, there were 772 drug overdose deaths in this age group in 2015.

This recent rise “certainly is a red flag,” said Bradley Stein, a child and adolescent psychiatrist and senior physician policy researcher at the Rand Corp., who was not involved in the report. However, Stein noted, because the overall number of drug overdose deaths among teens in this age group is relatively small, it’s possible that the recent rise is just statistical noise rather than a true increase. In other words, more data will be needed to determine whether this marks a new trend.

Still, “any uptick at all [in drug overdose deaths] is certainly something that has to get our attention,” Stein said.

The majority of overdose deaths in this age group, 80 percent, were unintentional. The rate of suicides resulting from overdose was higher among females (22 percent) than males (13.5 percent), the study found.

The report analyzed the types of drugs involved in teen overdose deaths, finding that opioids had the highest death rate, followed by benzodiazepines, which include such drugs as Valium and Xanax.

Stein noted that while people often focus on opioids as the biggest culprit in drug overdose deaths, it’s often a combination of drugs that leads to overdose, and the mixture of opioids with benzodiazepines can be particularly deadly.

The study also found that there has been a spike in teen overdose deaths involving heroin and synthetic opioids (such as fentanyl) in recent years, while there has been a decrease in deaths involving semi-synthetic opioids, which include prescription painkillers such as hydrocodone and oxycodone. This mirrors a trend seen in adults and suggests that while efforts to reduce prescribing of opioid painkillers may be working, these actions are “not a silver bullet” for solving the opioid crisis, Stein said.

Stein said it’s unclear why teen drug overdose deaths decreased from 2007 to 2014 while overdose deaths increased in other age groups. But he speculated that efforts to prevent opioid use or educate people about the risks of these drugs might have a bigger effect on teens. More research is needed to understand which interventions work best for which demographic groups, he said.

Still, even with prevention efforts, teens may become addicted to opioids, and there is still a need to push for better opioid addiction treatments for this age group, Stein said.

— Live Science