Almost 9,000 children and teenagers died from opioid poisoning from 1999 to 2016, and annual deaths increased threefold over the 18 years, a team of researchers at Yale University reported Friday.

The finding suggests the opioid epidemic will likely continue, the team said, unless legislators, public health officials, doctors and parents do more to keep the drugs out of the hands of young people.

More than 80 percent of the deaths to children and teens were unintentional, the researchers reported in the Journal of the American Medical Association. Five percent were from suicide and about 2 percent from homicide.

Nearly a quarter of the children under 5, and 35 percent of those younger than 1, were the victims of homicide.

Heroin was the cause of death for 24 percent of deaths to teens 15 to 19 years old. Between 2014 and 2016, synthetic opioids led to the deaths of nearly a third of all prescription and illegal opioid deaths among older teens.

The Yale researchers found that methadone was associated with 36 percent of the children's deaths. In many cases, parents or other adults in the children's lives used methadone to manage pain or treat addiction.

The risk of children misusing other people's methadone is "particularly relevant," the researchers wrote, as more people with opiod use disorder are getting medication as part of their treatment. That means more children will be exposed to methadone and buprenorphine in the coming years unless "further safeguards" are implemented.

The mortality rate for methadone peaked in 2007, however, and has been declining since. The Food and Drug Administration issued a public health advisory in 2006 warning doctors about the use of methadone for pain.

Dr. Marc Fishman is an addiction psychiatrist and professor at the Johns Hopkins University School of Medicine who treats teens and young adults with opioid use disorder.

He says the results are alarming because deaths to children and teens are increasing the same way as they are for adults – they start with pills, turn to heroin and die from the synthetic opiod painkiller fentanyl.

Young people also seek treatment far less often that adults, Fishman says, which makes it harder to track youth opioid use.

The American Academy of Pediatrics recommends that doctors prescribe teens medication-assisted treatment for opioid addiction.

"Even though we're treating patients better with medication, it’s a wake up call to be as careful with these medications than any others," Fishman says.

Jada Walker, a Kentucky woman who used methadone to treat an addiction to opioids, told the USA TODAY Network in 2016that she kept her methadone in a lock box so it was safe from her young children. Fishman says that's exactly what patients using medication-assisted treatment need to do.

There are some encouraging signs in the numbers. The National Institute for Drug Abuse reported this month that teenage opioid misuse has fallen to a record low in the 43-year history of its Monitoring the Future survey.

The use of prescription opiods and other narcotics other than heroin in the previous year is at 3.4 percent among 12th graders, a significant drop from the 4.2 percent in 2017.

Last year was the first the Centers for Disease Control and Prevention's Youth Risk Behavior Survey included a question about the misuse of prescription opioids. Fourteen percent of U.S. high school students, or nearly 1 in 7, reported ever misusing prescription opioids.

“With illicit opioid use at generally the lowest in the history of the survey, it is possible that being in high school offers a protective effect against opioid misuse and addiction,” said Dr. Nora Volkow, director of the National Institute on Drug Abuse. “We will be focusing much of our new prevention research on the period of time when teens transition out of school into the adult world and become exposed to the dangerous use of these drugs.”

Devin Reaves, 36, says his opioid addiction started when he was 16. He became hooked when he got a 30-day prescription to an opioid to manage the pain from having his wisdom teeth removed.

He says he went through the prescription in three days. Once he realized how easy it was to get the drugs, he was taking the pills in friends' houses and on the street. That led to heroin in college, and an intervention by his mother and a drug counselor when he was 24.

Reaves has been in recovery for 11 years. He now teams up with CDC's Rx Awareness Campaign to publicize safe prescription drug practices, including keeping opioids out of the reach of children.

Reaves says he reminds clients that opioid use disorder is a brain disease, not a moral failing. When he goes to the doctor or dentist, he talks about his history of substance use, and makes it clear he does not want opioids.

Far fewer teens are now getting opioids.

Only 1.7 percent of high school seniors reported misusing Vicodin in the past year, down from a peak of 10.5 percent 15 years ago. One in 25012th graders reported using heroin in the past year.

Nearly 36 percent of all opioid overdose deaths in the United States involve a prescription opioid. Such deaths have increased by about five times since 1999.

More than 200,000 people died from overdoses related to prescription opioids from 1999 to 2017. There were more than 17,000 overdose deaths from prescription opioids in 2017.

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