Even as the opioid epidemic dominated national attention over the past decade, the rate of overdose deaths involving cocaine, methamphetamine and other stimulants tripled, a new study on veterans suggests.

More than half of the 3,631 veterans who died from overdoses involving these drugs between 2012 and 2018 also had other substances in their systems, the study finds. In this group, most of those other substances were opioids, including both synthetic and prescription opioids.

But the other half of fatal veteran overdoses involving stimulants resulted from stimulant overdose without the presence of opioids. Of those overdoses involving stimulants and other non-opioid substances, three-quarters included alcohol as a factor in their deaths.

Most of the veterans whose overdoses were included in the study—70%—had not received any treatment in an addiction clinic in the year before they died. However, in line with the increased attention to opioids, those who died from a combination of opioids and stimulants were more likely to have received addiction treatment, or to have been diagnosed with a substance use disorder.

The study, published in Addiction by a team from the University of Michigan Addiction Center, the U-M Injury Prevention Center and the VA Center for Clinical Management Research, shows the key role of polysubstance use by those at risk for overdose.

The authors note that better access to treatment, especially for residents of rural areas and those who have experienced homelessness, is needed for veterans and others. They also note limited medication-based treatments to help individuals reduce their use of methamphetamine or cocaine; multiple medication-based treatments are available for those who have opioid or alcohol use disorders.

The study also highlights disparities in overdose risk from stimulants. For instance, one-third of all the overdose deaths involving stimulants were in Black veterans, as were two-thirds of the deaths from cocaine alone.

Rural residents were more likely to die from methamphetamine alone or in combination with other substances; if opioids were present, they were more likely to be prescription opioids rather than synthetic opioids.

"We have been so focused on opioids that we are missing the tremendous increase in people who are using multiple substances, as well as those using stimulants only, when we know that many people don't stick to just one substance," said Lara Coughlin, PhD, a psychologist specializing in addiction who is an assistant professor in the U-M Department of Psychiatry. "The fact that so many of those who died of an overdose had not received substance use disorder treatment is especially concerning."

This is important, she explained, because psychotherapy treatments have proven effective for stimulant use disorder, but these are typically available only in addiction treatment settings.

Coughlin points out that people who use methamphetamine or cocaine can experience heart damage that puts them at greater risk of death, especially if they also use opioids, which depress the respiratory system. The study found that 62% of the overdoses involving stimulants were among veterans aged 45 to 64.

"We need to build better awareness of the role of stimulants as a risk factor for overdose, and of the need for those who have stimulant use disorders to be referred for treatment, regardless if they are also using opioids," said Coughlin. "We know that cocaine and methamphetamine are much more likely to be adulterated with fentanyl or other synthetic opioids now, so those who use them need to be equipped with rescue doses of naloxone to use and need to know about the risk for overdose in case they or someone they're with experiences an unexpected, life-threatening reaction."

In addition to Coughlin, the study's authors include senior author and U-M/VA addiction psychiatrist Lewei (Allison) Lin, MD, MS, as well as Lan Zhang, PhD, Amy S.B. Bohnert, PhD, Donovan T. Maust, MD, M.S. and Jason Goldstick, PhD. All but Zhang are members of the U-M Institute for Healthcare Policy and Innovation.