Is Cannabis being used as a substitute for non‐medical opioids by adults with problem substance use in the United States? A within‐person analysis

Abstract

Background and Aims Ecological studies have suggested that Cannabis legalization might have led to a decrease in opioid overdose deaths. Such studies do not provide information about whether individuals are substituting Cannabis for opioids at different points in time. The current study assessed the magnitude of the daily association between Cannabis and opioid use in individual adults with and without pain who use non‐medical opioids. Design Prospective cohort study. Setting The greater New York area and a suburban inpatient addiction program. Participants Adults with problem substance use who use non‐medical opioids, recruited from May 2016–June 2019. The analytical sample included 13 271 days of observation among 211 participants (64% male, 41% white, 78% unmarried, 80% unemployed, mean age 43 years). Measurements Participants completed interviewer‐ and self‐administered computerized surveys, and then responded to an interactive voice response (IVR) system daily for the following 90 days. The main exposures, Cannabis use and pain, were defined as responding affirmatively to the IVR question: ‘Did you use Cannabis yesterday?’ and endorsing moderate or severe pain at baseline, respectively. The main outcome, non‐medical or illicit opioid use during 90‐day follow‐up, was defined as responding affirmatively to IVR question: ‘Did you use heroin yesterday?’ or ‘Did you use prescription opioids more than prescribed or without a prescription yesterday?’. Findings The mean IVR completion rate was 70%. The unadjusted odds ratio (aOR) indicating same‐day use of Cannabis and opioids was 2.00 [95% confidence interval (CI) = 1.54–2.59]. Controlling for demographic characteristics, recruitment method, opioid types at baseline and pain, the aOR was 1.86 (95% CI = 1.44–2.41). A test of interaction between pain and Cannabis use to determine if the association of Cannabis with opioid use differed between people with moderate‐to‐severe pain and less‐than‐moderate pain was inconclusive. Conclusions Among US adults with problem substance use who use non‐medical opioids, the odds of opioid use appear to be approximately doubled on days when Cannabis is used. This relationship does not appear to differ between people with moderate or more severe pain versus less than moderate pain, suggesting that Cannabis is not being used as a substitute for illegal opioids.

Effects of combined THC and heroin vapor inhalation in rats

“…Almost two-thirds of individuals in one sample first used heroin while co-using cannabis (Olthuis et al 2013 ) and 50–60% of individuals in heroin- and methadone-maintenance treatment for opioid use disorder were co-using cannabis (Musshoff et al 2010 ). On a day-by-day basis, cannabis use doubles the risk of non-medical opioid use in adults with problematic substance use (Gorfinkel et al 2021 ). Thus, although cannabis may have the potential to reduce opioid use in medical patients, there is also a clear risk for cannabis to increase the non-medical use of heroin from adolescence into middle age.…”

Illegal drug market responses to state recreational cannabis laws

“…However, evidence from other studies suggests that opioid measures decline after MCL implementation [22,[40][41][42][43][44]. Our findings may inform the debate on whether opioid use decreases with cannabis liberalization, and suggest alternative mechanisms beyond substitution or complementarity patterns, including changes in law enforcement, prices, supply and potency [22,[39][40][41][42][43][44][45]. Of note, as STRIDE prices are not representative and subject to other limitations discussed below [46,47], our associations may reflect these issues and should be interpreted with caution.…”

“…We cannot fully rule out that demand increases contributed to opioid price increases. A recent study documented that, among opioid-using adults, the odds of opioid use doubled on days that participants used cannabis, suggesting that opioids might be complements of cannabis [39]. However, evidence from other studies suggests that opioid measures decline after MCL implementation [22,[40][41][42][43][44].…”

Association patterns of cannabis abuse and dependence with risk of problematic non-substance-related dysregulated and addictive behaviors

“…Regarding substance use, cannabis-related problems were singled out for the present study for practical and theoretical reasons. Beyond the evidence that cannabis is addictive and thus cannabis abuse presents many of the characteristics observed in other addictive disorders [ 36 , 37 ], cannabis is the most frequently used illegal drug in western countries [ 1 ], and has been previously linked to sedentary leisure activities, and, particularly, to digital media use [ 3 , 10 , 38 , 39 ]. Therefore, there are at least two reasons why cannabis-related problems are expected to be linked to non-substance-related dysregulated/addictive behaviors.…”