Associations between prescription and illicit stimulant and opioid use in the United States, 2015–2020

•Severity of prescription stimulant use is related to cocaine/methamphetamine use.•Cocaine use and prescription stimulant misuse are significantly associated.•Methamphetamine use rates did not differ between prescription opioid or stimulant misuse.•Targeted prevention and screening of prescription stimulant misuse may reduce harm.