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. Author manuscript; available in PMC: 2025 Jan 1.
Published in final edited form as: J Stud Aff Res Pract. 2023 May 16;61(1):86–102. doi: 10.1080/19496591.2023.2177104

Alcohol and cannabis co-use: Receptiveness to treatments and application to intervention planning

Ashley C Helle 1, Cassandra L Boness 2, Joan Masters 3, Kenneth J Sher 4
PMCID: PMC10947103  NIHMSID: NIHMS1871995  PMID: 38504868

Abstract

Given the prevalence of alcohol and cannabis co-use among college students, prevention for co-use is crucial. We examined hypothetical receptiveness to substance-specific interventions among students who reported co-use. Students who use alcohol and cannabis were more receptive to alcohol interventions than cannabis interventions. Campus prevention experts should consider offering evidence-based alcohol-focused interventions as a potential pathway for decreasing substance use among college students who engage in co-use.

Keywords: alcohol use, cannabis use, college students, co-use, treatment, prevention

Introduction

Background

Recent national surveys have identified that 63% of college students reported past 3-month alcohol use (70% reported lifetime use) and 23% endorsed past 3-month cannabis use (37% reported lifetime use) (ACHA, 2021). Heavy alcohol consumption is also common and problematic among college students. Recent estimates suggest nearly 30% of college students meet criteria for a past year alcohol use disorder (AUD) (Arterberry et al., 2020; Grant et al., 2015). AUD and heavy use are associated with negative consequences, including physical and sexual assault, unintentional injury and death, unprotected sex, social and interpersonal problems, and academic problems, such as low grade point average (GPA) (Arria & Jernigan, 2018; Merrill & Carey, 2016; Mundt & Zakletskaia, 2012; Piazza-Gardner et al., 2016). College students also report a high prevalence of past-year cannabis use (42%) and approximately 8.6% of students meet criteria for a past year cannabis use disorder (CUD), defined as 2 or more of 11 symptoms according to the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (American Psychiatric Association, 2013; Arterberry et al., 2020; Grant et al., 2015; Schulenberg et al., 2019). Cannabis use among college students is associated with lower GPA and academic achievement (Buckner et al., 2010; Phillips et al., 2015; Suerken et al., 2016), increased risk of motor vehicle crashes (Asbridge et al., 2012; Pearson et al., 2017), and increased risk of other mental health problems (Volkow et al., 2014). Given their prevalence and associated problems, alcohol and cannabis use are important areas of focus for college health and prevention providers and student affairs experts.

Alcohol and Cannabis Co-Use

We also see high rates of students that use both alcohol and cannabis. Among a sample of nearly 5,000 college students, over half reported lifetime use of cannabis and alcohol (Looby et al., 2021). Twenty-six percent of Missouri college students reported using both alcohol and cannabis (referred to from here forward as “co-use”) in the past year (Partners in Prevention [PIP], 2021). It should be noted that this use may or may not occur in the same setting (e.g., simultaneous use). Data from Missouri schools also indicates that students who use alcohol at higher risk levels, including binge drinking and frequent binge drinking, were more likely to have used cannabis than students who do not binge drink. Indeed, 55% of students who binge drink and 64% of students who frequently binge drink report having used cannabis in the past year (PIP, 2021).

There are serious correlates of co-use, including: increased use of each substance (McCabe et al., 2006; Midanik et al., 2007; Subbaraman & Kerr, 2015), more use-related negative consequences (Briere et al., 2011; Green et al., 2019; Sokolvksy et al., 2020; Subbaraman & Kerr, 2015), poorer academic achievement (Jackson et al., 2020; Meda et al., 2017; Páramo et al., 2020), and greater likelihood of alcohol dependence and other forms of mental health concerns, such as depression (Midanik et al., 2017) when compared to students who solely use alcohol or cannabis. It is essential that administrators are aware that co-use is a major concern on campuses. Understanding co-use and student perspectives can help campuses be prepared to address co-use through their administrative budget planning and prevention and intervention efforts.

In addition to risk factors previously noted, there exist heightened concerns around co-use given the relatively recent legalization of cannabis in some states (e.g., Illinois, Michigan) and associated increases in use (e.g., see Smart & Pacula, 2019). Research suggests that having more than one substance use disorder negatively impacts treatment response, pointing to the importance of co-use focused interventions (Yurasek et al., 2017). Given these heightened concerns, and limited resources available on campuses for prevention and intervention efforts, it is evident that co-use of alcohol and cannabis among college students should be a focus of campus health and prevention.

Prevention and Treatment

Research is beginning to elucidate the motivations and consequences of alcohol and cannabis co-use (Arterberry et al., 2020; Sokolovsky et al., 2020). The better we understand co-use among college students, the better prepared we will be to develop, test, and implement effective campus intervention strategies. Despite the well-known negative consequences associated with co-use and resulting need for co-use interventions among college students, little research has focused on co-use treatment specifically. At this stage, higher education preventionists would benefit from understanding how existing treatments for a single substance may impact behavior change and reach students in need of prevention or treatment, especially among those who co-use.

There exist some non-substance-specific treatment approaches, such that the principles and techniques from a given treatment may be applied across substances. There are also substance-specific treatments and prevention efforts geared toward (or “advertised” for) specific substances, particularly on college campuses. For example, the Brief Alcohol Screening and Intervention for College Students (BASICS) is specific to alcohol and many existing harm reduction strategies, such as safe-ride programs, primarily/only include alcohol in their messaging. Given there are no explicit treatments for co-use, but there are evidence-based treatments for alcohol and cannabis use independently, it may be most efficient to determine if existing treatments can reach college students who co-use. For example, some research has examined the secondary effects of alcohol-focused interventions on cannabis use, demonstrating that alcohol-focused approaches (e.g., brief motivational interventions), can be effective in reducing alcohol use and the co-use of cannabis (see Yurasek et al., 2017 for a review). As such, there may be value in connecting college students who co-use to specific interventions (e.g., alcohol-focused interventions such as BASICS; mental health interventions) as a means of concurrently reducing their cannabis use.

Current Study

In addition to studying the efficacy of treatments that target co-use, it is important that we understand receptiveness, or openness, to various prevention and treatment approaches, particularly among individuals that co-use, given their high-risk status. Our overarching research question is: Are students who co-use more or less open to certain intervention approaches depending on the type, modality, or focus (e.g., alcohol or cannabis)? To address this question, the current study examined college students’ hypothetical receptiveness to intervention approaches that target alcohol and cannabis separately, and evaluated readiness to change alcohol and cannabis use, with the intention that this information may used to improve prevention and treatment delivery on college campuses.

Study Aims

This research study had two primary aims. First, we evaluated readiness to change alcohol use and receptiveness to alcohol-focused treatments among students who (a) only drink alcohol, and those who (b) co-usei to determine if students who use both substances are different than those who only drink alcohol regarding receptiveness to alcohol treatments. Second, among students who engaged in co-use, we examined readiness to change alcohol use and cannabis use (separately) and receptiveness to interventions addressing alcohol use compared to interventions for cannabis use. This aim provides (a) a closer look at what students in a high-risk group (i.e., co-use group) may be receptive to in terms of efforts to address alcohol and cannabis use separately and (b) identifies characteristics of students who use both alcohol and cannabis in terms of pathways to interventions targeting substance use (e.g., Are students who co-use more receptive to attending an intervention focused on alcohol or cannabis? Does the type of intervention matter?). With prior research identifying that changing alcohol use can impact cannabis use, and given the prevalence of alcohol use on campuses, as well as the relative availability of alcohol-focused prevention and treatment efforts compared to cannabis use, this research aims to provide insights into ways to maximize existing programs and approaches, based on student receptiveness.

Defining Co-Use

Given the relatively recent focus on understanding “co-use” in substance use research, the term is not yet operationalized in a standard and consistent manner; thus, terminology and conceptualizations vary in the literature (e.g., “overlapping use” is sometimes used to describe co-use). For the present study, we operationalize co-use as the endorsement of alcohol and cannabis use within the past 12 months, whether or not use overlaps within a given episode. We do not have sufficiently detailed data to indicate whether participants used the substances simultaneously, within the same day or episode. Our focus is on co-use as an indicator of perhaps using the substances at the same time, but not necessarily. This operationalization is appropriate for the present study given the focus is on receptiveness to intervention among college campuses. Theoretically, a student that uses both substances (even if not within the same episode) may benefit from intervention for each substance. It is important to note that co-use can also represent concurrent (not overlapping) and simultaneous (in same episode) use, among other definitions (Linden-Carmichael et al., 2019; Patrick et al., 2018). Although distinct, research has examined the overlap, finding 82–93% of college students who used more than one substance concurrently also used the substances simultaneously (Martin et al., 1992).

Materials and Methods

Participants and Procedure

College students from a large Midwestern university (enrolled in Introductory Psychology courses) who endorsed any alcohol and/or cannabis use in the past 12 months (any level of use one or more times in past 12 months) were invited to participate in a survey. The current investigation is part of a larger study (Helle et al., 2021) focused on predictors of hypothetical student receptiveness to treatment. Data were collected between October 2019 and April 2020. The present study (n = 430) focuses on two subsets of the original sample, specifically, the students that endorsed alcohol use only in the past 12 months (n = 155), and students that endorsed co-use in the past 12 months (n = 275). A “cannabis use only” group is not included given the low number of students in the sample that reported using cannabis only. Participants had a mean age of 18.95 years (SD = 2.18) in the alcohol-only group and 18.94 (SD = 1.55) in the co-use group. All participants reported on demographic information (Table 1).

Table 1.

Participant Demographics

Entire Sample (n = 430)
 Alcohol-only Group (n = 155)
 Co-Use Group (n = 275)
N % N % N %
Sex
 Female 280 65% 114 74% 166 60%
 Male 150 35% 41 26% 109 40%
Gender
 Women 279 65% 115 74% 164 60%
 Men 148 34% 40 26% 108 39%
 Gender-queer or Gender non-conforming 2 <1% 0 0% 2 1%
 Other 0 0% 0 0% 0 0%
 Decline to respond 1 <1% 0 0% 1 <1%
Race/Ethnicity (could endorse >1)
 White 383 89% 137 88% 246 89%
 Black 35 8% 13 8% 22 8%
 Hispanic 19 4% 6 4% 13 5%
 American Indian 4 1% 1 1% 3 1%
 Alaska Native 1 <1% 0 0% 1 <1%
 Guamanian 1 <1% 0 0% 1 <1%
 Hawaiian 3 1% 1 1% 2 1%
 Other Pacific Islander 1 <1% 0 0% 1 <1%
 Asian Indian 4 1% 2 1% 2 1%
 Chinese 5 1% 2 1% 3 1%
 Filipino 6 1% 2 1% 4 1%
 Japanese 3 1% 1 1% 2 1%
 Korean 2 <1% 0 0% 2 1%
 Vietnamese 1 <1% 1 1% 0 0%
 Asian (other) 2 <1% 0 0% 2 1%
 Another Race 4 1% 1 1% 3 1%
 decline to respond 2 <1% 1 1% 1 <1%
Year in School
 1st 325 76% 118 76% 207 75%
 2nd 68 16% 26 17% 42 15%
 3rd 21 5% 9 6% 12 4%
 4th 14 3% 2 1% 12 4%
 5th and beyond 2 <1% 0 0% 2 1%
Substance-Related Variables a M SD M SD M SD
 Alcohol: age of first use 16.05 1.76 16.74 1.81 15.67 1.62
 Cannabis: age of first use 16.43 1.57 - - 16.40 1.63
 Alcohol frequency: days used per year 60.86 57.39 44.60 54.84 69.77 56.90
(range: 1.5–365) (range: 1.5–365) (range: 1.5–274)
 Cannabis frequency: days used per year 84.37 129.32 - - 94.36 133.43
(range: 0.5–365) - (range: 0.5–365)
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a

Frequency items added after data collection began (entire sample: alcohol items N = 390, cannabis items = 280; alcohol-only group: N = 138; co-use group: alcohol items N = 252, cannabis items = 250).

All measures were completed online, via the Qualtrics survey platform, and compensation was awarded in the form of class credit. Participants reported on hypothetical intervention receptiveness and readiness to change respective to the substance(s) endorsed; therefore, the alcohol-only subset did not answer questions about cannabis use, cannabis interventions, and/or interest in changing cannabis use as in the co-use sample. All participants that used alcohol reported on alcohol-related consequences.

Measures

History of Treatment Utilization

All participants were asked to indicate if they had ever participated in alcohol, cannabis, or emotional/mental health treatment.

Consumption

Participants reported on their age of first use and past-year frequency for alcohol, with response options on a scale from 1 (1–2 times in the last year) to 10 (every day), consistent with the National Institute on Alcohol Abuse and Alcoholism’s recommended items for assessing alcohol consumption (NIAAA, 2004). Using items from the Daily sessions, Frequency, Age of onset, and Quantity of Cannabis Use inventory (DFAQ-CU; Cuttler & Spradlin, 2017), participants were asked to report on their age of first use of cannabis and past-year frequency for cannabis use, with response options ranging from 1 (less than once a year) to 12 (more than once a day). For consistency across substances, response options for frequency of use were converted to number of days in the past year (e.g., a response of 1–2 times in last year=1.5 days; once per month=12 days). Only a subset of individuals completed questions on frequency of alcohol (n = 390) and cannabis (n = 280) use (based on their lifetime use of either substance) and on alcohol consequences (n = 381) because items were added after data collection had started.

Hypothetical Interest in Change Strategies and Intervention Receptiveness

Participants were asked to indicate which approach(es) to behavior change they would consider if they were hypothetically interested in changing their use. The question was asked separately for alcohol and cannabis (when applicable) and participants could select more than one option. The options presented to participants included: (a) cutting down on use [referred to as “reduce use” for brevity], (b) stop using all together [referred to as “abstain” for brevity], (c) another option, or (d) none.

For alcohol and cannabis separately, participants were asked to rate how receptive they would be to 23 different intervention types. The intervention types encompass both prevention- and treatment-based approaches and were selected based on prior research (i.e., Epler et al., 2009) that was the basis for the larger study replication and extension, examination of recent advances in interventions (e.g., technological-based interventions), consultation with university prevention specialists, and a focus group with undergraduate research assistants. These were hypothetical situations (“If I were interested in changing my alcohol use, I would consider…”) rated from 1 (strongly disagree) to 6 (strongly agree). Interventions were grouped in seven categories: (1) individual/group therapy [in person, with professional]; (2) informal workshops and harm reduction approaches; (3) medication; (4) peer/family interactions; (5) primary care provider appointment; (6) remote/telehealth; (7) self-help. A receptiveness rating of 4 [agree] or higher on one or more items within a category represents receptiveness to that category.

Readiness to Change Questionnaire (RCQ)

The RCQ (Heather & Rollnick, 1993) is a 12-item measure that assesses stages of change: precontemplation (not thinking about changing use), contemplation (thinking about changing use), and action (already taking steps to change use). All items are a rated on a 5-point Likert scale ranging from −2 (strongly disagree) to 2 (strongly agree). The RCQ was administered separately for alcohol and cannabis, based on endorsement of lifetime use of the respective substance. In the present study, a summative scoring method was used (score was not calculated if 3+ items were missing). The RCQ sum score has been evaluated in prior studies and is a useful measure for indicating readiness to change (Budd & Rollnick, 1996). Internal consistency of the RCQ alcohol (ω=0.84) and cannabis (ω=0.86) in the present study was similar to Budd and Rollnick (1996) (α=0.85).

Brief Young Adult Alcohol Consequences Questionnaire (BYAACQ)ii

The BYAACQ (Kahler et al., 2005) is a 24-item checklist of past 30-day alcohol-related consequences across various domains (e.g., academic problems, interpersonal conflict). A sum of endorsed items was used in the present study (ω=.88).

Analytic Strategy

SAS 9.4 (SAS Institute, 2013) was used to conduct all analyses. Alcohol-focused items, including treatment receptiveness and change strategies of interest, were compared between the alcohol-only and co-use groups with chi-square tests. McNemar’s test was used to compare endorsement of alcohol- and cannabis-focused items within the co-use group. Independent (between group comparisons) and pairwise (within [co-use] group, comparisons) t-tests were used to examine differences between continuous variables (i.e., alcohol-related consequences, RCQ total score).

Limitations and Future Directions

Although this study provides an important look into student treatment receptiveness and co-use, it is not without limitations. First, this study was limited to college students (primarily first year) at one university in a Midwestern region of the U.S. This group of students may not be representative of other regions and/or types of institutions. Larger samples across institutions with a geographic distribution representing various cannabis policies (e.g., laws related to medicinal cannabis) should be included in future examinations of receptiveness to alcohol and cannabis interventions. Relatedly, this study asked about hypothetical receptiveness, therefore, it is unclear if the students were currently looking to change behavior and/or if the results would change as a result of the prompts (hypothetical or not).

Second, receptiveness to alcohol and cannabis interventions, but not receptiveness to co-use interventions, were assessed. This limits our ability to draw conclusions about targeting co-use with co-use specific approaches. Future research should examine both the effectiveness and delivery of such modalities, as well as student receptiveness, as compared to approaches that target a single substance.

Third, co-use was defined as using both alcohol and cannabis in the past year, though not necessarily at the same time. As described earlier, there are various ways to define co-use and co-use can include concurrent and/or simultaneous use, so there are important substance-specific considerations, such as half-life. Given that types of co-use may be differentially related to outcomes (e.g., simultaneous use associated with more consequences than concurrent use; Linden-Carmichael et al., 2020), future work should include a more nuanced look at co-use within the realm of prevention, in addition to continued work focused on mechanisms and consequences of co-use.

Finally, this study focused on alcohol only and co-use group comparisons, given alcohol prevention is already a primary focus at many institutions. We should also examine cannabis-only as a third comparison group, as well as examine key differences across approaches. For example, future research should examine the potential value in the sequencing and content of interventions for alcohol and/or cannabis. For example, are substance-specific or dual (alcohol and cannabis) focused interventions superior? Do intervention approaches (e.g., abstinence v. moderation) vary based on substance? Is there a specific sequencing of interventions that results in better outcomes and/or does addressing substances simultaneously result in the best outcomes? Examination of best practices for designing and/or implementing intervention approaches (e.g., focus on one substance, address underlying mechanisms of addiction across substances) are important to consider. Considerations include addressing both substances simultaneously, as evidence for common substance use disorder mechanisms grows and seemingly fails to support the notion of only addressing one substance at a time (Drobes et al., 2002).

Results

History of Treatment

In this sample, having a history of engaging with mental-health services was more common (39%, n=168) than alcohol (7%, n=31) or cannabis (5%, n=23) services. Within the alcohol-only sample, significantly more students reported a history with mental health treatment services (34%; n=53) compared to a substance-specific treatment (6%; n=9), McNemar’s χ2(1)= 33.38, p<0.001. A similar pattern was observed within the co-use sample; 42% (n=115) reported a history of mental health treatment, but only 11% reported a history of substance use treatment, McNemar’s χ2(1)=63.76, p<0.001. Within the co-use group, there was no significant difference between having a history of alcohol versus cannabis treatment.

Alcohol v. Co-Use Group (Between-Group Comparisons)

Here we describe differences between the alcohol-only and co-use groups on (a) alcohol consumption variables, (b) alcohol-related readiness to change, (c) interest in reduction versus abstention for alcohol, (d) receptiveness to alcohol-interventions, and (e) alcohol-related consequences. Students in the alcohol-only group reported a later onset of drinking (16.74yrs) compared to students in the co-use group (15.67yrs), t(385)=5.97, p< .0001. Frequency of alcohol use was higher in the co-use group compared to the alcohol-only group, t(388) = −4.23, p<.0001. The co-use group reported a significantly higher number of alcohol-related consequences (M=6.33, SD=4.75) compared with the alcohol-only group (M=3.76, SD=3.86), t(328.65)=−5.74, p<0.001 (see Table 1).

Alcohol-related readiness to change was compared between students in the alcohol-only and co-use groups. Students who reported co-use were in more advanced stages of change for alcohol (closer to change behaviors as opposed to not thinking about change) compared to students that only drank alcohol (Table 2). In both groups, the majority of the students reported that if they were interested in changing their substance use behavior, they would be interested in reducing drinking, whereas fewer were open to abstention strategies (Table 2). However, there were no significant differences between the groups regarding interest in reduction or abstention strategies for alcohol use. Similarly, there were no significant differences between groups for hypothetical intervention receptiveness for addressing alcohol use (Figure 1). Across both groups, close to or more than half of the students reported receptiveness to all categories of intervention with the exception of medications, in which approximately one-third endorsed receptiveness. Individual intervention options within each of the seven broader categories are included in Supplemental Table 1.

Table 2.

Interest and readiness to change variables among college student drinkers and college students who drink alcohol and use cannabis

ALCOHOL-ONLY GROUP (n = 155) CO-USE GROUP (n = 275) Between-Group Comparisons (A) v. (B) Within-Group Comparisons (B) v. (C)
(A) alcohola
 (B) alcohola,b
 (C) cannabisa
 Chi-square (df = 1) McNemar’s Chi-square (df = 1)
Interest in Changing Use n % n % n %
 If wanted to change my use, I’d be open to (select all that apply):
  Strategies to help cut down 113 73% 212 77% 147 53% 0.94 45.43 ***
  Strategies to stop using all together 33 21% 41 15% 73 27% 2.83 17.07 ***
  Another option 3 2% 8 3% 7 3% 0.38 0.91
  None of these 19 12% 24 9% 95 35% 1.37 57.94 ***
 Readiness to Change Usec M SD M SD M SD independent t (df = 426) paired t (df = 270)
Readiness to Change Sum Score 14.69 7.20 16.41 8.01 16.97 9.65 −2.24 * −0.82
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Note.

*

p < 0.05

**

p < 0.01

***

p < 0.001.

a

Values represent responses to alcohol-specific items and/or intervention options (i.e., (A), (B)), and cannabis-specific items/intervention options (C).

b

Comparisons between (B) and (C) use cases in which co-use participants have a value for alcohol and cannabis interventions. Therefore the Ns in column (B) may be slightly different in the McNemar comparisons if participants had any missing ratings. These differences are very slight, and if present, the percentages change 1% or less.

c

Readiness to Change (RCQ) sum score calculated if 10+ of 12 items were completed. All items scaled 0 to 4.

Figure 1. Receptiveness to various alcohol-specific interventions: Between-group comparisons of students who only drink alcohol (N = 155) to those who use alcohol and cannabis (N = 275).

Figure 1.

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Bars reflect the percentage of students in each group that were hypothetically receptive (i.e., participant rated “agree” or higher) for one or more individual alcohol-specific interventions within the respective intervention category (see Supplemental Table 1 for interventions within each category). Values above bars reflect between-group comparisons (Chi-square test, df = 1). No differences were significant.

Co-Use Group: Alcohol v. Cannabis (Within-Group Comparisons)

Here we describe differences within the co-use group on (a) alcohol and cannabis consumption, (b) alcohol and cannabis readiness to change, (c) hypothetical interest in strategies for reduction versus abstention for alcohol and cannabis, and (d) hypothetical receptiveness to alcohol and cannabis interventions. Among the students in the co-use group, there was a significantly earlier onset of alcohol use (15.67yrs) than cannabis use (16.40yrs), t(247)=−6.79, p<.0001. Among students in the co-use group, on average, cannabis was used more frequently than alcohol over the past year t(249)=−2.75, p< .01 (Table 1).

Within the co-use group, students had a similar ‘readiness’ level to change alcohol and cannabis use. When examining approaches to changing use (e.g., abstain, reduce) within the co-use group, a significantly higher proportion of individuals were open to reduction strategies for alcohol (77%) compared to cannabis (53%) (Table 2). On the other hand, openness to abstention strategies was endorsed more frequently for cannabis (27%) compared to alcohol (15%), although openness to abstinence was still lower relative to reduction. Interestingly, among students that use both substances, approximately one-third indicated they wouldn’t be open to either approach (abstinence or reduction) for cannabis, but only 9% indicated they wouldn’t be open to either approach for alcohol. Hypothetical receptiveness to interventions were endorsed at a significantly higher rate when the intervention was specific to alcohol, as opposed to cannabis (Figure 2). This was the case for six of the seven intervention categories (openness to medication was lowest in co-use group, respective to alcohol and cannabis). Differences between intervention types within the categories provide a more nuanced examination of these areas (Supplemental Table 1).

Figure 2. Receptiveness to various alcohol-specific and cannabis-specific interventions: Within-group comparisons among students who use alcohol and cannabis (N = 275).

Figure 2.

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Bars reflect the percentage of students in each group that were hypothetically receptive (i.e., participant rated “agree” or higher) for one or more individual interventions listed within the respective category (see Supplemental Table 1 for interventions within each category). Co-Use Alcohol = percentage of students in co-use group who were open to the respective intervention if specific to alcohol. Co-Use Cannabis = percentage of students in the co-use group who were open to the respective intervention if specific to cannabis. Values above bars reflect within-group comparisons (McNemar’s Chi-square test, df = 1). ***p < .001.

Discussion

Alcohol and Cannabis Use

Compared with students who only drink alcohol, students who engaged in co-use (i.e., used alcohol and cannabis in the past year) started drinking at an earlier age, consumed alcohol more frequently over the past year, and reported a greater number of alcohol-related consequences. Students within the co-use group reported using cannabis more frequently than alcohol, though there was greater variability in frequency of cannabis use than alcohol use among these students.

Receptiveness to Intervention Types

College students who engaged in co-use were similar to students who only used alcohol in terms of alcohol intervention receptiveness, with approximately half or more of the students being most open to some variation of self-help, telehealth, individual/group therapy, workshops, primary care, and peer/family-based approaches. Students that engaged in co-use were more open to each hypothetical intervention (e.g., self-help, therapy, primary care) when focused on alcohol compared to cannabis, with the exception of medication-based approaches, in which receptiveness was relatively low for alcohol and cannabis (<30% in each group).

Interest in Reduction and Abstention Strategies

Relatedly, students who engaged in co-use were similar to those that only used alcohol in terms of their interest in strategies focused on alcohol reduction. It appears as though students who engaged in co-use would be just as open to alcohol interventions and reduction strategies as students who used alcohol only. Within the co-use group, preferred strategies for changing behavior varied based on substance, such that abstention strategies were more commonly endorsed for cannabis, whereas reduction strategies were more commonly endorsed for alcohol (reduction was the most commonly endorsed option for each substance; Table 2).

Readiness to Change

Students in the co-use group were further along in readiness to change their alcohol use, compared with students who only drank alcohol. More advanced readiness to change in the co-use group may be an indirect reflection of increased consequences, thus feeling change may be more beneficial and suggesting these students may be particularly ready to change alcohol use. There was no difference in hypothetical receptiveness to alcohol interventions between the alcohol-only and co-use group, even though the co-use group was in a more advanced stage of change, on average. Stages of change for alcohol use and cannabis use did not differ within the co-use subgroup. These results may suggest that students in the co-use group feel similarly about their readiness to change their alcohol and cannabis use but would prefer different types of change strategies for each substance and are more open to alcohol interventions in general.

Implications and Recommendations

Given the results of this research study, we suggest two overarching areas of focus for student affairs and prevention experts: practice-based recommendations and campus-level recommendations for planning prevention and treatment programming. Basic ideas within each area are outlined here though it should be noted that each recommendation may be accomplished through various avenues and/or steps given each institution’s needs and resources.

Practice-Based Recommendations

(1). Offer Evidence-Based Alcohol-Focused Strategies.

Offering alcohol interventions may be one way to reach students who use alcohol only, but importantly, also to reach those that co-use alcohol and cannabis. Students that use both substances tend to have more negative outcomes and consequences, and more challenges in treatment (Yurasek et al., 2017); however, evidence has also demonstrated that changes in alcohol use can reduce cannabis use (White et al., 2015). Further, many college campuses have ongoing, alcohol harm reduction and treatment efforts, whereas cannabis efforts are likely not as prevalent given the only relatively recent attention to risky cannabis use among students. If students are most receptive to alcohol interventions, this may provide a pathway to seeking or receiving support, and may contribute to change in cannabis use among students who use both substances. Further, given those who co-use were open to strategies to help cut down on alcohol use (should they choose to change), college campuses that offer alcohol harm reduction strategies may be better received by this group. A helpful resource to identifying possible alcohol-focused prevention approaches for college campuses is the freely-available College Alcohol Intervention Matrix (CollegeAIM; NIAAA, 2019), a tool that outlines alcohol prevention strategies by cost and effectiveness (https://www.collegedrinkingprevention.gov/collegeaim/). Focusing on ways to reach students who engage in co-use is an important topic given that the results of the study found students who co-use reported a higher level of readiness to change compared to those that used alcohol only. Future work examining readiness to change and openness to alcohol versus cannabis or other services among students who engage in co-use using qualitative approaches will provide useful insights into reach and implementation of services.

(2). Expand Prevention Services Beyond Alcohol.

In addition to providing evidence-based alcohol strategies as a way to open the door to discussing cannabis, campuses should consider providing services with other-substance foci. Campuses main priority within the substance use realm is often alcohol, given the focus on risky alcohol use among college students in the media, social norms of the campus, or folklore from families and/or the community. Data from this study demonstrate that students are engaging in cannabis use, and co-use of alcohol and cannabis, which may incur additional risks. Campuses should consider implementing evidence-based strategies for harm reduction and treatment focused on cannabis and other substances besides alcohol. As research on interventions specific to co-use becomes more prevalent, there may be additional intervention modalities or components to consider (e.g., Arterberry et al., 2021).

(3). Screen for Co-use/Polysubstance Use.

In addition to providing services for alcohol and substance use, screening for multiple substances when students are engaging in substance-related services, particularly if focused on a single substance, may be useful. Given the number of students that engage in co-use, it would be beneficial to screen for cannabis and other substance use for students engaged in alcohol services, for instance. Students in this study reported receptiveness to many types of intervention approaches. Thus, using screening to identify students to refer to other services may be beneficial. Here are a number of examples that illustrate how this might be accomplished: (a) When students are engaged in BASICS (Brief Alcohol Screening for College Students), screening for cannabis or other substances could take place so that further resources can be shared; (b) During campus alcohol screening events, questions about cannabis and/or co-use could be added, including the use of diagnostic or risk screening measures such as the Alcohol (AUDIT) or Cannabis Use Disorder Identification test (CUDIT); (c) When students are engaged in iCHAMP or other evidence-based cannabis harm reduction conversations, alcohol screening could occur; (d) Professionals working in student conduct should have referral resources for students related to cannabis use and alcohol use, despite the specific substance used in the conduct infraction; (e) Campus health and/or counseling centers could screen for alcohol and cannabis use, and consider co-use in their practice with students. This last point is also related to the following recommendation about integration of services across campus.

(4). Integrate Alcohol and Substance Prevention with Other Services across Campus.

Students in the alcohol-only and co-use groups had higher rates of prior mental health service utilization as compared to substance-focused services. Given the potential of greater availability of mental health as opposed to substance interventions (Mojtabai, 2005) and greater stigma associated with addiction compared to other mental health concerns (Barry et al., 2014), focus on mental health services may provide another pathway to intervention among students who co-use who could benefit from intervention. Very few students in the co-use group (11%) have ever received substance treatment, but nearly half (42%) reported prior experience with mental health services. The intersection of mental health and substance treatment is of great relevance regardless, given high rates of psychiatric comorbidity. As we see a shift toward integration of services and a focus on interdisciplinary approaches to college health (e.g., intersection of mental health and medical offices; joining of student conduct with student counseling), the further integration of screening and treating substance use in other health settings may be of great value to students and their receptiveness for substance-interventions. Additionally, future research should focus on identification of best practices of integration of substance use services to primary mental health service outlets.

(5). Use a Variety of Strategies.

The results of this study and the larger parent study (Helle et al., 2021) demonstrate that students are receptive to more than one type of approach for alcohol and cannabis prevention (e.g., self-help, individual therapy), and over 50% of students that co-use are receptive to nearly all types of alcohol intervention types (Figure 1). From a college prevention standpoint, one way to reach many students across risk levels is to offer a mix of strategies and interventions. For example, alcohol prevention may have a place in the college health center, as well as counseling, and peer education groups. Although the specific strategies may vary widely across settings, offering a variety is consistent with the evidence (NIAAA, 2019), and may allow more opportunities to meet students where they are at in regards to their use and to have the most success at reducing substance-related risk.

Campus-Level Recommendations for Planning

(1). Conduct Relevant Campus Assessment.

Evidence-based assessment and evaluation is key to identifying individuals that may benefit from referrals, as well as measuring the current status of substance use among a campus body. It is important for campuses to engage in their own assessment of risky substance use behaviors in order to best guide their implementation of evidence-based strategies to address risky alcohol use, risky cannabis use, or co-use. Many campuses already implement an annual student assessment of health behaviors; thus, including items related to co-use of substances and openness to programming/strategies could be beneficial to inform implementation efforts in future years.

(2). Secure Administrator Support for Addressing Co-use.

National data (NCHA) and school-level data (e.g., this study) demonstrate that college students are using cannabis and many are using it in addition to alcohol. Administrators who oversee health services, counseling services, and health promotion services can share recent data on students use of alcohol and other substances with administration. Such data can provide direction for campuses to address both substances based on the national data and needs of their own individual campuses (see campus-level recommendation #1).

(3). Establish Partnerships between Student Services/Student Affairs and Academic Faculty.

Institutions of higher education have the benefit of housing professionals from multiple disciplines and with varying types of expertise. For example, there are applied experts who work in student affairs, student health, and prevention. There are also experts on the ‘academic’ or research side of the institution. These two groups of “applied” and “research/academic” based faculty and staff do not always work hand in hand on prevention matters; however, the collaboration between the two groups may be very fruitful in advancing the study and implementation of best practices for alcohol and cannabis co-use prevention on a given campus. As an illustration, the authors of this paper include members from student affairs as well as psychology faculty who primarily conduct research. Such partnership has allowed for a multi-faceted perspective on student co-use and related recommendations.

Conclusions

College students who use alcohol and cannabis are similar to college students that only use alcohol when it comes to openness to hypothetical intervention approaches for and readiness to modify alcohol use. Among students who co-use, there is more openness to changing alcohol use than cannabis use. Compared to students that only drink alcohol, co-using students tend to be more ‘advanced’ in their alcohol readiness to change, but co-using students are equally ready to change their alcohol and cannabis use. Finally, intervention approaches targeting alcohol and/or mental health more generally may be an effective way to reach students who use alcohol and cannabis, and may be a pathway to treatment for addressing risky cannabis use.

Given these results, we provided overarching recommendations. First, we list practice-based recommendations, specifically, that student affairs and prevention experts: (1) consider how they may screen for and address cannabis use in the context of evidence-based alcohol interventions; (2) expand to provide services beyond alcohol; (3) screen for alcohol and cannabis co-use; (4) consider integration of alcohol, cannabis, and substance use prevention in the context of other areas, such as medical and/or mental health settings; (5) consistent with CollegeAIM recommendations, we suggest that a variety of strategies be implemented, which has the potential to increase the reach of prevention efforts to students, particularly given their hypothetical receptiveness to various approaches. We also list campus-level intervention planning recommendations, including: (1) implement campus-level assessment of alcohol and cannabis co-use to inform evidence-based selection and implementation of strategies; (2) work with administration to gain support for addressing co-use of alcohol and cannabis; (3) establish partnerships between student affairs/services and academics to synergize campus efforts to address risky substance use on campus.

Supplementary Material

Supplemental Table

Acknowledgements:

This work was supported by National Institutes of Health under grants: T32AA013526 (PI: Sher), F31AA026177 (PI: Boness), and K08AA028543 (PI: Helle).

Footnotes

Disclosure Statement: There are no disclosures or conflicts of interest to report.

i

Additional information on operationalization is provided in Current Study: Defining Co-Use.

ii

Given this study was a secondary data analysis of a larger project (Helle et al., 2021), not all variables were assessed for both alcohol and cannabis (i.e., consequences). Therefore, there was no assessment of cannabis consequences available for inclusion in current analyses.

Contributor Information

Ashley C. Helle, University of Missouri.

Cassandra L. Boness, Center on Alcohol, Substance use, And Addictions at the University of New Mexico.

Joan Masters, Partners in Prevention in the Division of Student Affairs at the University of Missouri.

Kenneth J. Sher, Psychology at the University of Missouri.

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