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

The purpose of this review is to provide an overview of the existing literature on the relationship between the co-use of cannabis and alcohol including (1) epidemiology, comorbidity, and associated consequences of cannabis and alcohol use disorders; (2) preclinical and clinical laboratory studies examining behavioral pharmacology of cannabis and alcohol co-use; and (3) clinical outcomes related to co-use. Findings from the literature reviewed suggest that the co-use of alcohol and cannabis is associated with additive performance impairment effects, higher and more frequent consumption levels, increased social and behavioral consequences such as driving while impaired, and greater likelihood of the experiencing comorbid substance use and mental health disorders. Furthermore, co-use may be associated with worse clinical outcomes, yet there are few studies examining the development and evaluation of interventions on reducing the co-use of cannabis and alcohol. There is a need for more rigorous and longitudinal research studies on the co-use of cannabis and alcohol to glean a more complete understanding of the relationship between the two substances. Findings can be used to develop and refine intervention strategies to successfully reduce cannabis and alcohol co-use.

Background: The COVID-19 pandemic resulted in lockdowns that had an impact on alcohol and cannabis use behavior. During the height of the early lockdowns, many individuals shifted to using alcohol and cannabis in solitary contexts (e.g., Wardell et al., 2020). Solitary drinking is a non-normative behaviour that can predict severe alcohol problems and is associated with coping-motivated drinking (Keough et al. 2018; Skrzynski & Creswell, 2020). Similarly, solitary cannabis use is associated with cannabis use disorder and using cannabis to cope (Spinella et al., 2019). Further, co-use of alcohol and cannabis is related to negative consequences such as alcohol use disorder, depressive symptoms, and impaired driving (Yurasek et al., 2017). As there has been limited research on solitary alcohol and cannabis co-use, this study examined substance use motives and consequences associated with solitary use of both alcohol and cannabis among co-users during the pandemic. Methods: Canadians (N=149; 46% female; mean age = 31 years old) who reported co-use of alcohol and cannabis completed an online survey approximately 6-8 weeks into the first COVID-19 lockdown. Participants reported on past 30-day alcohol and cannabis use, solitary use, motives, and problems (i.e., Short Inventory of Problems and Marijuana Problems Scale). Participants were divided into two groups: those reporting predominantly solitary use of both alcohol and cannabis during the lockdown (solitary co-users; n=61) and those reporting predominantly social use of one or both substances during the lockdown (social co-users; n=88). Logistic regression was used to examine the unique associations of drinking motives and cannabis motives with co-use group (solitary vs. social), and to examine if the solitary co-use group was more likely to report alcohol and cannabis problems (controlling for alcohol and cannabis use). Results: Coping motives for drinking were associated with greater likelihood of being in the solitary vs. social co-use group after controlling for other drinking motives and alcohol use (OR=2.02, p=.023). Conversely, none of the cannabis use motives were significantly associated with membership in the solitary vs. social co-use group. Additionally, compared to social co-users, solitary co-users had higher odds of reporting alcohol problems, including one or more physical problems (OR=2.37, p=.033), intrapersonal problems (OR=3.95, p=.002), and social problems (OR=2.79, p=.022), after controlling for alcohol use. Cannabis-related problems did not differ between solitary and social co-users. Conclusions: Findings provide insight into the motives and consequences of solitary alcohol and cannabis use among co-users during the early stages of the COVID-19 pandemic. These findings suggest that interventions should target co-users who are using both alcohol and cannabis in a solitary context during the pandemic as they appear to be at higher risk for alcohol-related problems. Future research should examine the long-term outcomes of solitary co-use throughout the COVID-19 pandemic. Given that it is not known if the solitary co-users in this study were engaging in simultaneous use of cannabis and alcohol (i.e., using both substances on the same occasion), future ecological momentary assessment (EMA) studies should focus on understanding solitary simultaneous use during the pandemic.

Co-use of alcohol and cannabis, or use of these substances simultaneously such that their effects overlap, is prevalent and growing. Compared to alcohol-only use, co-use of alcohol and cannabis is associated with greater negative consequences, such as heavier drinking, more cognitive issues, and risky behavior. Impulsivity (i.e., tendency toward rash action without consideration of consequences) and perceived norms (i.e., a social influence by which individuals adjust their behavior to that of their peers) are two factors related to increased substance use among young adults, but few studies have examined their role in co-use behaviors. Consequently, the purpose of this study was to examine the associations between impulsivity, perceived norms, co-use of alcohol and cannabis, and alcohol- and cannabis-related consequences. Participants were 209 (72.7% female) college students between 18 and 25 (M = 20.01, SD = 1.50) from universities in Rhode Island who completed an online survey regarding their co-use of alcohol and cannabis behaviors. A sequential mediation model was examined whereby impulsivity (positive urgency, negative urgency, sensation seeking, lack of premeditation, and lack of perseverance) predicted alcohol- cannabis-related consequences through the influence of perceived norms (i.e., descriptive and injunctive norms) and level of frequency of co-use of alcohol and cannabis. The overall indirect paths between each impulsivity facet and co-use consequences were nonsignificant. Findings revealed that higher injunctive norms predicted higher frequency of co-use of alcohol and cannabis. Higher negative urgency predicted co-use of alcohol and cannabis consequences. Lastly, higher lack of premeditation predicted lower co-use of alcohol and cannabis. All other paths were nonsignificant. Overall, this study informed an understanding of the relationships between impulsivity, norms, and co-use behaviors. Although the indirect paths in the sequential mediation model were nonsignificant, negative urgency was related to greater co-use consequences, and greater injunctive norms predicted greater frequency of co-use. Findings also elucidated nuances between alcohol-only, cannabis-only, and co-use variables among a sample of individuals who engage in co-use. Information may be used to inform interventions tailored to co-use of alcohol and cannabis.

BACKGROUND: College students in the United States widely report using alcohol and cannabis as a sleep aid. Given the prevalence of sleep problems and insufficient sleep in this population, the high incidence in use and co-use of cannabis and alcohol is unsurprising. Current evidence does not support alcohol as an effective sleep aid and research on the relationship of cannabis to sleep is limited and inconsistent. Furthermore, the majority of current cannabis and sleep studies are limited to retrospective, person-level analyses even though there is a wide range of individual and day-level differences in reactivity to intoxication. PURPOSE: The aim of this study is to examine cannabis and alcohol use and their associations with sleep at both the between-person level (i.e., between-subjects comparison of chronic use behaviors) and within-person level (i.e., day-level comparison of use behaviors). METHOD: This study is a secondary analysis of longitudinal data obtained from a study characterizing the effects of simultaneous alcohol and cannabis use. Participants (n=341) completed surveys up to five times per day during two bursts of 4 weeks (54 days total) that occurred during two consecutive college semesters. Self-reported quantities of cannabis use (as number of uses) and alcohol use (as number of drinks), as well as bedtimes (night) and wake times (morning) were reported. Linear mixed models were conducted in SAS 9.4 to characterize between-person and within-person (person-mean centered) correlations of cannabis or alcohol use and sleep duration. RESULTS: Significant main effects of within-person cannabis (Estimate: 0.019, SE: 0.007, t=2.86, p=0.004) and alcohol (Estimate: -0.0402, SE: 0.0076, t=-5.28, p<0.001) use were found, as was a between-person main effect of average cannabis use (Estimate: 0.038, SE: 0.012, t=3.28, p=0.001) across the full study period. The between-person main effect of average alcohol use was not significant. CONCLUSIONS: The results suggested that generally heavier cannabis users sleep more than their non-using/generally light using counterparts and that they sleep more on nights following heavier use days. Interestingly, the relationship between alcohol and sleep differed between the between-person and within-person levels: alcohol use was dose-dependently associated with reduced sleep duration; however, in this sample, generally heavier alcohol users did not appear to differ in overall sleep duration compared to generally lighter alcohol users. Importantly, this sample included a wide range of substance users, none of whom were in treatment for a cannabis use disorder (CUD) or alcohol use disorder (AUD). Whether these patterns of dose-dependence would be observed over longer time periods or in individuals who meet criteria for CUD or AUD remains to be studied. Future studies will assess the effects of alcohol and cannabis co-use patterns as well as timing of consumption.

Prevention of violent behaviors (VB) in the early phase of psychosis (EPP) is a real challenge. Impulsivity was shown to be strongly related to VB, and different evolutions of impulsivity were noticed along treatments. One possible variable involved in the relationship between VB and the evolution of impulsivity is cannabis use (CU). The high prevalence of CU in EPP and its relationship with VB led us to investigate: 1/the impact of CU and 2/the impact of early CU on the evolution of impulsivity levels during a 3-year program, in violent and non-violent EPP patients. 178 non-violent and 62 violent patients (VPs) were followed-up over a 3 year period. Age of onset of CU was assessed at program entry and impulsivity was assessed seven times during the program. The evolution of impulsivity level during the program, as a function of the violent and non-violent groups of patients and CU precocity were analyzed with linear mixed-effects models. Over the treatment period, impulsivity level did not evolve as a function of the interaction between group and CU (coef. = 0.02, p = 0.425). However, when including precocity of CU, impulsivity was shown to increase significantly only in VPs who start consuming before 15 years of age (coef. = 0.06, p = 0.008). The precocity of CU in VPs seems to be a key variable of the negative evolution of impulsivity during follow-up and should be closely monitored in EPP patients entering care since they have a higher risk of showing VB.

The increasing co-use of e-cigarette and cannabis among youth has become a public health challenge. The present analyses aimed to identify prevalence and correlates of past-month co-use of e-cigarettes and cannabis among adolescents with and without prior tobacco use. For this panel study, 5 years of cross-sectional data (2014-2018) were used from 8th, 10th-, and 12th-grade adolescents in the Monitoring the Future study, a nationally representative survey of U.S. students. We examined prevalence and correlates of e-cigarettes and cannabis co-use among adolescents who had ever used tobacco (n = 15,136) and among those who had never used tobacco (n = 56,525). Adolescents who had ever used tobacco showed significantly higher rates of e-cigarettes and cannabis co-use compared to adolescents who had never used tobacco (17.1% vs. 2.2%, p < 0.01). Results from adjusted multinomial regression models showed that overall, Black and Hispanic adolescents tobacco users were less likely than Whites to co-use e-cigarettes and cannabis. Black adolescents who had used tobacco previously were more likely than Whites to have used cannabis exclusively. Black and Hispanic tobacco-naïve adolescents were more likely than Whites to have used cannabis exclusively, while Black tobacco-naïve adolescents were less likely to use e-cigarettes exclusively or co-use e-cigarettes and cannabis. Overall, males and twelve graders were more likely than males and eight graders to use or co-use cannabis or e-cigarettes, respectively. Among lifetime tobacco users, higher levels of parental education were associated with co-use of cannabis and e-cigarettes. Racial/ethnic-specific patterns of e-cigarette and cannabis co-use depends on adolescents' prior experience with tobacco. The higher rates of use and co-use of e-cigarettes and cannabis among prior tobacco users suggest that targeted interventions are needed for this group. Identified socio-demographic groups at higher risk of co-use of e-cigarettes and cannabis need to be further studied.

Although research has only recently started to examine the impact of cannabis use on stress response, there is some evidence that indicates acute and chronic impacts of cannabis on these processes. In this paper, we review processes involved in regulating the stress response and we review the influence of acute and chronic exposure to cannabis on patterns and regulation of the stress response. We also highlight the role of stress as a risk factor for initiation and maintenance of cannabis use. In this context, we examine moderating variables, including sex and life adversity. In light of recent observations indicating increasing prevalence of cannabis use during pregnancy, we provide additional focus on cannabis use in this vulnerable population, including how acute and chronic stress may predispose some individuals to use cannabis during pregnancy. While this line of research is in its infancy, we review available articles that focus on the perinatal period and that examined the association between cannabis use and various life stressors, including partner violence, job loss, and lack of housing. We also review psychiatric co-morbidities (e.g., post-traumatic stress disorder, anxiety). A better understanding of the way stress and cannabis use relate within the general population, as well as within certain subgroups that may be at a greater risk of using and/or at greater risk for adverse outcomes of use, may lead to the development of novel prevention and intervention approaches.

ABSTRACTObjective(s)With growing cannabis use in the US, it is crucial to understand the impact of recreational use on sinonasal diseases like chronic rhinosinusitis (CRS), allergic rhinitis (AR), and chronic rhinitis (CR).MethodsThis cross‐sectional study leveraged the NIH AllOfUs database to query patient surveys assessing cannabis usage frequency (lifetime never, monthly, weekly, or daily within the past 3 months) and consumption route (smoking or non‐smoking). Cannabis users were matched to never users for demographics, healthcare visit frequency, and insurance. A stringent logistic regression model calculated odds ratios (OR) of developing AR, CRS, or CR after survey completion. Cox regression hazard ratios (HR) compared consumption routes.ResultsTwenty‐five thousand one hundred sixty‐four cannabis users were matched with 113,418 never users. Users demonstrated significantly lower odds of AR, CRS, and CR than never users. For CRS, the ORs compared to never users are as follows: daily users 0.64 (95% CI 0.53–0.78), weekly users 0.61 (95% CI 0.48–0.77), and monthly users 0.80. For AR, the ORs were 0.64 (95% CI 0.58–0.71) for daily users, 0.62 (95% CI 0.54–0.71) for weekly users, and 0.69 (95% CI 0.58–0.80) for monthly users. For CR, the ORs were 0.61 (95% CI 0.47–0.79) for daily users, 0.64 (95% CI 0.47–0.87) for weekly users, and 0.41 (95% CI 0.26–0.65) for monthly users. There was no significant difference between smokers and non‐smokers (HR 0.64, 95% CI 0.27–1.5).ConclusionThere is an inverse, associative relationship between cannabis use and sinonasal disease. This relationship is insufficiently understood, and there remain significant concerns about the impact of cannabis use, especially smoking, on airway pathologies.Level of Evidence4.

Heavy drinking is common among men who have sex with men (MSM) and significantly increases HIV acquisition risk. MSM who report heavy drinking also report higher cannabis use, which has also been associated with sexual behaviors known to elevate HIV transmission risk. Despite evidence of associations at the between-subjects level, the effects of alcohol and cannabis use on sexual risk behavior among MSM who engage in heavy drinking are largely unknown. The current study used ecological momentary assessment to examine the between- and within-subject associations of heavy drinking, cannabis use, and sexual behavior. This is a secondary data analysis of a study on alcohol intoxication and sexual decision making that included 115 MSM who reported cannabis use and were not using pre-exposure prophylaxis (PrEP) at baseline. Participants reported daily alcohol and cannabis use and sexual activities over 6 weeks. Multilevel multinomial regression was used to evaluate how alcohol and cannabis use were associated with sexual behaviors. Higher alcohol use was associated with higher rates of intercourse at the between-persons level and a higher likelihood of all sexual behaviors at the event level. In contrast, cannabis use at the between-person level was associated with an increased rate of condomless anal intercourse relative to both anal intercourse with a condom as well as no sex. At the within-person level, cannabis was associated with an increased likelihood of anal sex with or without a condom relative to no sex. Cannabis and alcohol may have independent effects on sexual risk behavior among MSM. Interventions addressing sexual health among MSM who engage in heavy drinking should also consider the additive risks of cannabis use.

Cancer survivors are at increased risk for cardiometabolic comorbidities following cancer treatment, which may be further exacerbated by cannabis and alcohol use. We aimed to examine the direct relationships of cannabis, alcohol, and the co-use of both substances with cardiometabolic risk factors and to explore disparities by race/ethnicity and sex. Cross-sectional data were extracted from adult cancer survivors in the "All of Us" from 2018 to 2022. Cannabis use was defined as occasional or frequent/regular cannabis use (vs. never) in the past 3 months and hazardous alcohol intake (AUDIT-C >3 for females; AUDIT-C >4 for males) versus nonhazardous in the past year, respectively. Co-use was defined as participants who engaged in regular cannabis and hazardous alcohol intake. We identified binary cardiovascular, immune, and metabolic system biomarkers, with high values defined by clinically established cutoffs or >75th percentile. We used multivariable logistic regression adjusting for sociodemographic and clinical factors. In our sample (N = 7,054), 7.6% were Hispanic, 6.2% were Black, and 86.2% were White cancer survivors. Less than 5% of Hispanic and White survivors reported substance co-use compared with 7% of Black survivors. Compared with never-users, co-users were 1.58 (95% confidence interval, 1.14-2.19) more likely to have high blood pressure. No significant associations were found between co-use and immune biomarkers or sex differences. Co-use of cannabis and hazardous alcohol may worsen high blood pressure in survivors, who are at higher risk for cardiometabolic comorbidities. The study investigates substance use and cardiometabolic biomarkers, urging much research on their effects on cancer survivors.

Purpose of Review Alcohol and cannabis are substances commonly used by people with or made vulnerable to HIV. With changing cannabis legalization, cannabis use has been on the rise, including simultaneous use (co-use) with alcohol. Prior reviews have assessed patterns, correlates, and consequences of alcohol and cannabis co-use. We conducted a scoping review to examine alcohol and cannabis co-use and HIV risk, treatment, and prevention outcomes. Recent Findings We identified 818 unique articles across seven databases through December 2024, of which, 28 met criteria. There was substantial heterogeneity in the conceptualization of co-use, measurement, and analysis methods. Many studies employed cluster analyses, with alcohol and cannabis co-use often included in the context of polysubstance use. Only one study utilized event-level methods to assess simultaneous use and sex behaviors. Findings on the relationship between alcohol and cannabis co-use and antiretroviral medications (ARV) outcomes and sex behaviors are mixed, though several studies suggest that co-use may be associated with poorer ARV adherence and increased engagement in sex behaviors that increased HIV risks. Summary This review highlights substantial heterogeneity in how alcohol and cannabis co-use is conceptualized and measured. Few studies examined simultaneous use specifically or disentangle co-use from broader polysubstance patterns. Research prioritizes standardized and event-level assessment can enhance accuracy of measurement and elucidate contextual factors for alcohol and cannabis co-use. Understanding how alcohol and cannabis co-use affects populations disproportionately impacted by HIV can inform more effective and tailored HIV treatment and prevention strategies.

Co-use of alcohol and cannabis among young adults is often associated with more alcohol consumption than alcohol-only use, yet little work has examined cannabis use specifically during heavy drinking. Much of the work examining heavy drinking has focused on heavy episodic drinking (HED, 4+/5+ drinks/occasion for females/males); however, young adults report drinking levels that far exceed this, frequently reporting high-intensity drinking (HID; 8+/10+ drinks/occasion for females/males), double the HED threshold, which confers greater risk of acute negative consequences. This study examined whether day-level co-use (vs. alcohol-only use) was associated with greater odds of heavier drinking levels: HID vs. HED vs. moderate drinking (1-3/1-4 drinks/occasion for females/males). We explored whether within-person variations in cannabis use characteristics (frequency, form, and quantity) differentiated moderate drinking, HED, and HID on co-use days. Young adults who reported simultaneous alcohol and cannabis use (N = 318) from three US universities completed five repeated daily surveys for 54 days reporting number of drinks and number of cannabis uses (i.e., frequency/events), forms, and quantity. Participants reported increased likelihood of HID and HED versus moderate drinking on co-use versus alcohol-only days. HID versus HED did not differ between co-use and alcohol-only days. On co-use days, heavier drinking was more likely on days with more cannabis use. The form of cannabis used and the use of multiple versus single forms of cannabis were not associated with drinking level. Yet, HID was more likely than HED and moderate drinking when more grams of flower were used and HID was also more likely than moderate drinking when more hits of concentrates were used. Findings show heavy drinking (HID, HED) was more likely than moderate drinking on co-use days and cannabis use characteristics may influence drinking levels. Co-use interventions may benefit from a focus on heavy drinking and cannabis use characteristics.

Increases in cannabis use among young people has heightened concern about the potential interactive health effects of cannabis with other drugs. We examined the longitudinal association between concurrent and simultaneous (SAM) co-use of alcohol and cannabis in young adulthood on mental health symptoms, substance use behaviors, and substance-related harms two years later. Data were drawn from Time 5 (T5; n = 464; 46% male) and 6 (T6; n = 478; 45% male) of the Victoria Healthy Youth Survey. At T5, 42% of participants used alcohol-only, 13% used concurrently, 41% used SAM, 1% were cannabis only users, and 3% abstained from cannabis and alcohol. Boys were more likely to use SAM. Higher T5 SAM use frequency was associated with heavier use of substances, more substance-related harms, and symptoms of psychosis and externalizing problems at T6. T5 Concurrent use was associated with conduct symptoms, illicit drug use, and alcohol use disorders at T6 relative to alcohol-only use. Cannabis is commonly used with alcohol and the findings suggest that any co-use (concurrent or simultaneous) may be problematic in young adulthood. Public health messages need to explicitly inform consumers about the possible consequences of using both alcohol and marijuana and the addictive pharmacological impact of using them together.

Cannabis use is highly prevalent among individuals presenting with their first episode psychosis (FEP), and a substantial proportion of individuals continue to use cannabis following the onset of the illness. Longitudinal research following up FEP patients has now started to explore in more detail the impact of cannabis use on long-term prognosis of psychosis, implicating continued cannabis use as a risk factor for an unfavourable illness course of psychosis. Since cannabis use is one factor amenable to treatment, it constitutes an attractive interventional target for early intervention. As such, a nuanced understanding of how exposure to cannabis affects the long-term course of psychosis is paramount, to help clinicians and carers to formulate the best possible treatment choices for individuals with a first episode psychosis. This chapter will focus in more detail on questions concerning the impact of cannabis use on the illness course of psychosis, including an overview of its effects on clinical and functional outcome dimensions, an assessment of causality, and a discussion on the interplay between cannabis use and other factors implicated in long-term prognosis of psychosis.

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