Cannabis use during alcohol treatment is associated with alcohol-related problems one-year post-treatment

Patterns of Cannabis and Alcohol Co-Use: Substitution Versus Complementary Effects

PURPOSE

The purpose of this review is to discuss the literature regarding the concurrent use (co-use) of alcohol and cannabis and competing hypotheses as to whether cannabis acts as a substitute for (i.e., replacing the effects of alcohol, resulting in decreased use) or a complement to (i.e., used to enhance the effects of alcohol, resulting in increased use) alcohol. The impact of cannabis use on alcohol-related outcomes has received increased attention in the wake of ongoing legalization of cannabis for both medical and recreational purposes. Evidence for both hypotheses exists in the literature across a broad range of data collection methods and samples and is carefully reviewed here. In addition, various mechanisms by which cannabis may act as an alcohol substitute or complement are explored in depth with the goal of better understanding equivocal findings.

SEARCH METHODS

This review includes articles that were identified from a search for studies on alcohol and cannabis co-use, with a specific focus on studies exploring complementary versus substitution aspects of co-use. Search terms were included in Google Scholar, PsycINFO, MEDLINE, and Web of Science. Eligible studies were those that measured alcohol and cannabis co-use in human samples in laboratory, survey, or ecological momentary assessment studies, or that directly referenced substitution or complementary patterns of use.

SEARCH RESULTS

Search results returned 650 articles, with 95 meeting inclusion criteria.

DISCUSSION AND CONCLUSIONS

Results of this review reveal compelling evidence for both substitution and complementary effects, suggesting nuanced yet significant distinctions across different populations examined in these studies. Several mechanisms for the impact of cannabis use on alcohol-related outcomes are identified, including patterns and context of co-use, timing and order of use, cannabinoid formulation, pharmacokinetic interactions, and user characteristics (including diagnostic status), all of which may influence substitution versus complementary effects. This review will inform future research studies examining this topic in both clinical and community samples and aid in the development of treatment and prevention efforts targeting those populations most vulnerable to negative consequences of co-use. Finally, this review highlights the need for additional research in more diverse samples and the use of mixed-methods designs to examine both pharmacological and contextual influences on co-use.

Effects of cannabis use on alcohol consumption in a sample of treatment-engaged heavy drinkers in Colorado

BACKGROUND AND AIMS

Cannabis is commonly used among people who drink alcohol, but evidence suggests a nuanced relationship between alcohol consumption and cannabis use. In particular, among individuals undergoing alcohol treatment the impact of cannabis on alcohol intake may depend upon cannabis use frequency. We aimed to test the effects of within-day cannabis use on total drinks consumed and likelihood of binge drinking on a given day among all participants and compare these relationships between males and females and between individuals who reported infrequent and frequent cannabis use.

DESIGN

This observational study is a substudy of a larger randomized controlled trial (RCT). Individuals were included from the RCT if they reported any cannabis use and were divided into groups based on cannabis use patterns. Alcohol use was compared within and between groups.

SETTING

Individuals were recruited from 2016 to 2020 from community and university settings in Denver and Boulder, CO, USA.

PARTICIPANTS

Of the 182 individuals enrolled in the RCT, 96 cannabis-using subjects were included in these analyses.

MEASUREMENTS

Subjects completed a time-line follow-back (TLFB) at baseline, 4, 8 (end of treatment) and 20 weeks. Daily data on alcohol and cannabis use from the TLFB at all time-points were analyzed.

FINDINGS

Across the sample (n = 96), individuals drank approximately 29% fewer drinks [95% confidence interval (CI) = 18-39%, P < 0.001] and were 2.06 times (95% CI =1.37-3.08, P < 0.001) less likely to have a binge-drinking episode on days that cannabis was used compared with days that cannabis was not used. These patterns were observed in males, females and the infrequent and frequent cannabis use groups. Findings were inconclusive regarding differences in the association between cannabis use and alcohol outcomes when comparing males and females and when comparing infrequent and frequent cannabis use groups.

CONCLUSIONS

Heavy drinkers engaged in treatment to reduce their alcohol consumption who also use cannabis appear to increase their cannabis use on days when they reduce their alcohol consumption.

Potential for cannabis adaptation among participants in a drunk driving intervention

Background

Some alcohol interventions have been found to have the adverse outcome of increasing non-alcohol-related substance use. It is unknown, however, how changes in alcohol use over the course of alcohol ignition interlocks - a common DUI intervention - may impact other substance use.

Methods

Alcohol and cannabis use were measured using hair ethylglucuronide and Delta-9-Tetrahydrocannabinol concentrations in blood, respectively. Participants (N = 69) were measured at the interlock installation period and again 6-months later while the interlock was installed. A mixed ANOVA was conducted to examine changes in levels of ethanol and THC over time.

Results

On measures of marijuana use, there was a significant interaction effect between the group that increased alcohol use and time F(2, 66) = 7.863, p =.001; partial η ² =.192; as well as a main effect for time F(2, 66) = 21.106, p <.001; partial η ² =.242.

Conclusions

Installing interlocks may inadvertently increase cannabis use among those who decrease alcohol use. Crash risk associated with cannabis use is notably less than that of alcohol use, however, continued cannabis use may be problematic when the device is removed and alcohol use is expected to return to the higher pre-interlock levels.

Decreased drinking in adults with co-occurring cannabis and alcohol use disorders in a treatment trial for marijuana dependence: Evidence of a secondary benefit?

The purpose of the present study was to investigate whether cannabis dependent users who met criteria for a secondary diagnosis of alcohol use disorder (AUD) would increase their use of alcohol in response to decreasing their use of marijuana in a behavioral treatment trial for cannabis use disorder (CUD). This phenomenon is commonly known as "substance substitution." Participants were randomly assigned to one of four 9-session treatment conditions with cannabis and alcohol use measured at baseline, posttreatment, and at 4 follow-ups through 14 months. Of those enrolled (n = 198), 27 (13.6%) also met criteria for AUD. Linear mixed models were used to analyze alcohol use over time with cannabis use and time as predictors. Findings demonstrated that there were no associations between declines in cannabis use and changes in alcohol consumption in the full sample. However, among those with CUD who also had AUD, declines in cannabis use significantly predicted concurrent declines in alcohol use (p < .05). This study did not find evidence of substance substitution among individuals receiving treatment for CUD. Contrary to expectations, the results indicated that individuals with AUD were more likely to decrease, rather than increase, their alcohol use when they reduced their marijuana use. Treatment for CUD in this study appeared to result in improvements in substance use generally, at least for those with comorbid AUD.

A longitudinal examination of daily patterns of cannabis and alcohol co-use among medicinal and recreational veteran cannabis users

BACKGROUND

Prompted by the ongoing debate regarding whether cannabis serves as a complement to or substitute for alcohol, this study uses prospective data to examine daily associations between medicinal versus recreational cannabis and alcohol use in veterans.

METHODS

Three semi-annual waves of Timeline Followback Interview data were collected from a sample of veterans who reported co-using alcohol and cannabis on at least one day (N = 115; 56% medicinal users; 93% male; 62,100 observations). Linear mixed effects models were used to examine the association between daily cannabis use and number of drinks consumed across time for both medicinal and recreational users and to examine the frequency medicinal cannabis used to substitute for alcohol.

RESULTS

Compared to medicinal users, recreational users were more likely to drink more on cannabis use days relative to non-use days. Among medicinal users, those endorsing more frequent use of cannabis as a substitute for alcohol reported fewer number of drinks consumed on days when cannabis was used relative to non-use days.

CONCLUSIONS

Among veterans, recreational users are at greater risk for increased drinking when co-using cannabis at the daily level, an association that is stable over time. Medicinal users may be at lower risk for increased drinking on days when cannabis is also used, especially those who endorse using cannabis to substitute for alcohol. Findings help clarify the debate on cannabis-alcohol substitution or complementary associations in a sample of veterans and suggests that alcohol interventions should address cannabis use as a risk factor, especially for recreational users.

The Effects of Marijuana Use on Transitions through Stages of Alcohol Involvement for Men and Women in the NESARC I and II

Background: With the changing context of marijuana use, it is critical to identify effects of use. We extend previous work by examining whether marijuana use influences progression and remission through alcohol involvement stages for men and women. Methods: Data come from Waves I and II of the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC, n = 34,432). We assess the potential influence of marijuana use at Wave 1 on transitions across three latent statuses of alcohol involvement between waves. We apply propensity score weighting to account for shared risk factors. Results: Marijuana use was associated cross-sectionally and longitudinally with alcohol involvement statuses for both sexes. After propensity score adjustment, men with marijuana histories were 3.50 times as likely as men without such histories to transition from no to severe problems across waves relative to staying in the same status (p < .001). Women with marijuana histories were 1.74 times as likely as women without such histories to transition from no problems at Wave 1 to moderate problems at Wave 2 (p = .030) and 0.13 times as likely as women without such histories to transition from severe problems to no problems (p = .006). Conclusions: Results suggest that marijuana use impacts progression to more serious stages of alcohol involvement for both men and women, as well as hinders remission among women. Findings point to the importance of screening those with marijuana histories for alcohol problems, as well as the need to understand the mechanism of why marijuana use may increase the risk of alcohol problems.