Co-involvement of Opioids in Drug Overdose Deaths Involving Cocaine and Psychostimulants

● In 2019, 54% of overdose deaths involving psychostimulants also involved an opioid; the percentage varied by region, from 80% in the Northeast to 44% in the West. Deaths from drug overdose continue to contribute to the public health burden in the United States (1). The increase in the rate of drug overdose deaths involving cocaine and psychostimulants has been well-documented in recent years (1–4). This NCHS Data Brief provides additional information on drug overdose deaths involving cocaine and other psychostimulants (drugs such as methamphetamine, amphetamine, and methylphenidate) by examining the concurrent involvement of opioids. Trends from 2009 through 2019 and differences by census region in 2019 are presented.

• In 2019, 76% of overdose deaths involving cocaine also involved an opioid; the percentage varied by region, from 83% in the Northeast to 63% in the West.
• From 2009 through 2016, the rate of overdose deaths involving psychostimulants but no opioids was higher than the rate for deaths involving both drugs; from 2017 through 2019, the pattern reversed with a higher rate for deaths involving both psychostimulants and opioids.
• In 2019, 54% of overdose deaths involving psychostimulants also involved an opioid; the percentage varied by region, from 80% in the Northeast to 44% in the West.
Deaths from drug overdose continue to contribute to the public health burden in the United States (1). The increase in the rate of drug overdose deaths involving cocaine and psychostimulants has been well-documented in recent years (1)(2)(3)(4). This NCHS Data Brief provides additional information on drug overdose deaths involving cocaine and other psychostimulants (drugs such as methamphetamine, amphetamine, and methylphenidate) by examining the concurrent involvement of opioids. Trends from 2009 through 2019 and differences by census region in 2019 are presented.
From 2013 through 2019, the rate of drug overdose deaths involving both cocaine and opioids increased at a faster pace than the rate of overdose deaths involving cocaine without opioid involvement.
• After remaining stable from 2009 through 2013, the age-adjusted rate of drug overdose deaths involving cocaine more than tripled from 1.6 per 100,000 in 2013 to 4.9 in 2019 ( Figure 1). NCHS reports can be downloaded from: https://www.cdc.gov/nchs/products/index.htm. 1 Stable trend from 2009 through 2013, then increasing trend from 2013 through 2019, p < 0.05. 2 Increasing trend from 2009 through 2019, p < 0.05. NOTES: Drug overdose deaths involving cocaine were identified using International Classification of Diseases, 10th Revision underlying cause-of-death codes X40-X44, X60-X64, X85, or Y10-Y14, with a multiple cause-of-death code T40.5. Deaths with concurrent involvement of opioids also had multiple cause-of-death codes T40.0-T40.4 or T40.6. Age-adjusted death rates were calculated using the direct method and the 2000 U.S. standard population. Deaths may have involved other drugs in addition to cocaine and opioids. Access data table for Figure 1 at: https://www.cdc.gov/nchs/data/databriefs/db406-tables-508.pdf#1. SOURCE: National Center for Health Statistics, National Vital Statistics System, Mortality.
Deaths per 100,000 standard population In 2019, the percentage of cocaine-involved overdose deaths that also involved opioids varied by region.
• In 2019, 15,883 drug overdose deaths involving cocaine occurred in the United States. Of these, 75.5% also involved an opioid (Figure 2).
• The percentage of cocaine-involved overdose deaths that also involved an opioid varied by census region: 83.1% in the Northeast (highest), 78.1% in the Midwest, 70.9% in the South, and 63.0% in the West (lowest). 1 Significantly higher than Midwest, South, and West, p < 0.05. 2 Significantly higher than South and West, p < 0.05. 3 Significantly higher than West, p < 0.05. NOTES: Drug overdose deaths involving cocaine were identified using International Classification of Diseases, 10th Revision underlying cause-of-death codes X40-X44, X60-X64, X85, or Y10-Y14, with a multiple cause-of-death code T40.5. Deaths with concurrent involvement of opioids also had multiple cause-of-death codes T40.0-T40.4 or T40. 6

In 2019, the percentage of psychostimulant-involved overdose deaths that also involved opioids varied by region.
• In 2019, 16,167 drug overdose deaths involving psychostimulants occurred in the United States. Of these, 53.5% also involved an opioid (Figure 4).
• The percentage of psychostimulant-involved overdose deaths that also involved an opioid varied by census region: 79.6% in the Northeast (highest), 60.4% in the Midwest, 54.3% in the South, and 43.6% in the West (lowest). 1 Significantly higher than Midwest, South, and West, p < 0.05. 2 Significantly higher than South and West, p < 0.05. 3 Significantly higher than West, p < 0.05. NOTES: Drug overdose deaths involving psychostimulants with abuse potential were identified using International Classification of Diseases, 10th Revision underlying cause-of-death codes X40-X44, X60-X64, X85, or Y10-Y14, with a multiple cause-of-death code T43.6. Deaths with concurrent involvement of opioids also had multiple cause-of-death codes T40.0-T40.4 or T40. 6

Summary
The findings highlight increases in the co-involvement of opioids in drug overdose deaths involving cocaine and psychostimulants in recent years. In 2019, three-quarters of the 15,883 drug overdose deaths involving cocaine also involved one or more opioids. This percentage varied by region, with the highest percentage in the Northeast (83.1%) and the lowest percentage in the West (63.0%). From 2013 through 2019, the rate of overdose deaths involving both cocaine and opioids increased at a faster pace than overdose deaths that involved cocaine but no opioids.
Compared with the findings for cocaine, only 53.5% of the 16,167 drug overdose deaths involving psychostimulants in 2019 also involved one or more opioids. As with overdose deaths involving cocaine, the percentage varied by region, with the highest percentage in the Northeast (79.6%) and the lowest percentage in the West (43.6%). From 2009 through 2016, the rate of overdose deaths involving psychostimulants but no opioids was higher than the rate of deaths with opioids, while from 2017 through 2019, the rate was higher for overdose deaths involving both psychostimulants and opioids.

Definitions
Drug poisoning (overdose) deaths: Includes deaths resulting from unintentional or intentional overdose of a drug, being given the wrong drug, taking a drug in error, or taking a drug inadvertently.
Psychostimulants with abuse potential: Includes drugs such as methamphetamine, amphetamine, and methylphenidate.

Data source and methods
Estimates are based on the National Vital Statistics System multiple cause-of-death mortality files (5). Drug poisoning (overdose) deaths involving cocaine were defined as deaths with International Classification of Diseases, 10th Revision (ICD-10) underlying cause-of-death codes X40-X44 (unintentional drug poisoning), X60-X64 (suicide by drug poisoning), X85 (homicide by drug poisoning), or Y10-Y14 (drug poisoning of undetermined intent), with a multiple causeof-death code of T40.5. Drug poisoning deaths involving psychostimulants with abuse potential were defined as deaths with ICD-10 underlying cause-of-death codes X40-X44, X60-X64, X85, or Y10-Y14, with a multiple cause-of-death code of T43.6. Deaths with concurrent involvement of opioids had multiple cause-of-death codes T40.0-T40.4 or T40.6, in addition to T40.5 or T43.6. The decedent's state of residence was grouped into one of four census regions: Northeast, Midwest, South, and West (6).
Age-adjusted death rates were calculated using the direct method, adjusting to the 2000 U.S. standard population (7). Trends in age-adjusted death rates were evaluated using the Joinpoint Regression Program (Version 4.8.0.1) (8). Joinpoint software fitted weighted least-squares regression models to the rates on the logarithmic transformation scale. Analyses were set to NCHS Data Brief ■ No. 406 ■ April 2021 ■ 6 ■ allow a maximum of three joinpoints across the period, a minimum of three observed time points from any given joinpoint to either end of the data, and a minimum of four observed time points between any two joinpoints. The permutation tests for model (number of joinpoints) significance were set at an overall alpha level of 0.05 (9). Pairwise comparisons of rates were conducted using a z test with an alpha level of 0.05 (7).
Several factors related to death investigation and reporting may affect measurement of death rates involving specific drugs. At autopsy, the substances tested for and the circumstances under which the toxicology tests are performed vary by jurisdiction. This variability is more likely to affect substance-specific death rates than the overall drug overdose death rate. The percentage of drug overdose deaths that identified the specific drugs involved varied by year, ranging from 75% to 79% from 2009 through 2013 and increasing from 81% to 94% from 2014 through 2019. In 2019, at least one specific drug or drug category was mentioned in 94% of drug overdose deaths in the Northeast, Midwest, and West, and 93% in the South. Some drug overdose deaths may have involved other drugs in addition to cocaine, psychostimulants, and opioids. While this report emphasizes drug overdose deaths involving cocaine or psychostimulants with or without the involvement of opioids, all drugs mentioned as involved in the death were considered to have contributed to the death.

About the authors
Holly Hedegaard is with the National Center for Health Statistics (NCHS), Division of Analysis and Epidemiology. Arialdi Miniño and Margaret Warner are with the NCHS Division of Vital Statistics.