The Relationship between Frequency of Cannabis Use and Prescription Opioid Misuse Among Age Groups

Background and Purpose: Prescription drugs and cannabis are the two most commonly used illicit substances in America and have been shown to be correlated. Given the ongoing opioid crisis, prescription drug misuse represents a serious threat to the health of individuals in this country. This study further explores the relationship between cannabis use and prescription opioid misuse to increase understanding of how frequency of cannabis use is related to the likelihood of misusing prescription opioids and if this relationship is the same across age groups.

Methods: Data for this study comes from the combined 2017 through 2019 National Survey on Drug Use and Health (NSDUH), an annual survey of adolescents and adults. The sample was a combined n=168,725, with n=56,276 in 2017, n=56,313 in 2018, and n=56,136 in 2019. Age was categorized into younger adults (under 50 years old) and older adults (50 and over). Cannabis frequency was operationalized as less frequent (under 15 days a month) and frequent (15 or more days a month). Only people who had used cannabis at least once in the past month were included. Logistic regression was utilized to examine the effect frequent cannabis use had on the likelihood to misuse prescription opioids. Additional interaction effects were examined for cannabis frequency by age group.

Results: Around 52.1% of the sample was female, with 58.1% identifying as non-Hispanic white. Among adults 50 and over, 2.4% had misused a prescription opioid in the past year, while 5.1% of adults under 50 had misused a prescription opioid. Around 14.2% of adults under 50 had used cannabis in the past month, while approximately 5.8% of adults over 50 had used cannabis. Among past-month cannabis users, those that had used cannabis for 15 or more days in a month showed a significantly increased likelihood of having misused prescription opioids in the past year (OR= 1.40, p < 0.01, CI= 1.28 – 1.53). A significant interaction effect was observed for age group and cannabis frequency, with older adults who used cannabis more than 15 days a month having no significant difference in the likelihood of misusing prescription opioids. In contrast, adults under 50 who frequently used cannabis showed a significant increase in the likelihood of misusing prescription opioids (OR= 1.41, p < 0.01, CI= 1.29 – 1.55).

Conclusion and Implications: Results from this study indicate that frequent cannabis use represents an increased likelihood of past-year prescription opioid misuse for the general population of cannabis users. However, upon further investigation, this relationship is only observed for younger adults, with older adult cannabis users showing no difference in prescription opioid misuse, regardless of frequency of use. This could indicate that the reason for frequent cannabis use (e.g., for medical purposes, which is more common for older adults) impacts the level of risk for prescription opioid misuse.