Overdose deaths involving methamphetamine almost tripled in the United States between 2015 and 2019, according to a new study.

Researchers from the National Institute on Drug Abuse (NIDA) found frequent use of meth combined with other substances may have contributed to the increase in overdose deaths, HealthDay reports.

From 2015 to 2019, the number of overdose deaths involving psychostimulants other than cocaine (largely methamphetamine) rose from 5,526 to 15,489 — a 180% increase. The number of people who reported using methamphetamine only increased by 43% during the same period.

“We are in the midst of an overdose crisis in the United States, and this tragic trajectory goes far beyond an opioid epidemic. In addition to heroin, methamphetamine and cocaine are becoming more dangerous due to contamination with highly potent fentanyl, and increases in higher risk use patterns such as multiple substance use and regular use,” NIDA director Nora D. Volkow, M.D., one of the authors of the study, said in a news release.