Qualitative Examination of Simultaneous Alcohol and Cannabis Use Reasons, Evaluations, and Patterns among Heavy Drinking Young Adults

Abstract

Use of alcohol and cannabis together so their effects overlap (simultaneous use) is common among college students and associated with numerous negative consequences. The aim of this study was to gain insight into college students’ recent simultaneous use events in order to inform future studies (i.e., generate hypotheses, inform measures/assessments of simultaneous use, and identify factors influencing simultaneous use). Qualitative interviews of simultaneous use experiences among heavy drinking college students (n=38) were conducted to better understand reasons for simultaneous use, evaluations of simultaneous use events, and patterns of substance use during simultaneous use events. Findings indicated that students’ reasons for simultaneous use included traditional 4-factor motive types (i.e., social, conformity, enhancement, and coping), cross-fading motives, harm reduction motives (e.g., to drink less), and reactive/situational reasons (e.g., because it was offered/available). There was variability in participants’ subjective evaluations of how positive versus negative simultaneous use events were and how this compared to single substance use events. Evaluation of simultaneous use events depended on patterns of use, external and internal context, and consequences experienced. Additionally, patterns of simultaneous use including order of substances, timing of using each substance, and quantities of substances used were highly variable across participants. Notably, participants reported engaging in patterns of use they perceived to reduce negative consequences during simultaneous use events. Further research on reasons for simultaneous use and patterns of use may help identify simultaneous use occasions that result in greater risk; identification of high-risk simultaneous use occasions and evaluation of these occasions can then help inform targeted interventions.

Use of alcohol and cannabis are significant public health concerns, particularly among college students. Seventy-five percent of students report alcohol use and 42% report cannabis use (Schulenberg et al., 2019). Use of each of these substances individually is associated with significant social, physical, and legal consequences (Pearson et al., 2017; Read et al., 2006; Simons et al., 2012). Even more concerning, however, is that college students often report using both alcohol and cannabis simultaneously so their effects overlap (Brière et al., 2011; Terry-McElrath & Patrick, 2018). Three-fourths of college students who use both alcohol and cannabis report sometimes using these substances together so that their effects overlap (simultaneous use) and on average engage in simultaneous use at least twice per month (White et al., 2019). Simultaneous users report particularly high levels of both alcohol and cannabis use as well as serious negative consequences. Relative to single substance users, simultaneous users report higher rates of driving under the influence and alcohol-related accidents (Arterberry et al., 2017; Chihuri et al., 2017; Terry-McElrath et al., 2014), greater harm to social relationships, employment, academics, and mental health (Yurasek et al., 2017), and higher rates of alcohol and cannabis use disorders (Midanik et al., 2007; Subbaraman, 2016). Additionally, laboratory studies suggest simultaneous use is associated with synergistic cognitive impairment (Downey et al., 2013; Hartman et al., 2016).

Given the high prevalence and adverse effects of simultaneous use, identification of what drives simultaneous use among young adults is important in understanding this risky behavior and can inform prevention and intervention efforts. Qualitative methods are particularly useful for exploring details of lived substance use experiences. Such methods can provide nuanced insight into why and under what conditions simultaneous use occurs for young adults in a way that survey methods often cannot. Yet, there is only one qualitative analysis of youth and simultaneous use (Price Wolf et al., 2019). The goal of the current study was to use individual interviews to gain an in-depth understanding of simultaneous alcohol and cannabis use among heavy drinking college students, with a particular focus on why they decide to engage in simultaneous use, how they personally perceive (i.e., subjectively evaluate) their simultaneous use events, and precisely how they use alcohol and cannabis together during simultaneous use events (e.g., order, amounts).

Reasons for Simultaneous Use

Motivational models (Cooper, 1994; Cox & Klinger, 2011) suggest people drink and use cannabis for numerous reasons, and theorize that motives are one of the most proximal predictors of substance use. General motives for alcohol use and general motives for cannabis use are associated with the more specific behavior of simultaneous use. For example, Patrick et al. (2019) found elevated enhancement and conformity motives were associated with greater likelihood of simultaneous use versus single substance use (alcohol or cannabis use only). Elevated coping motives were associated with greater likelihood of simultaneous use versus alcohol-only use and elevated social motives were associated with greater likelihood of simultaneous use versus cannabis-only use.

Additionally, reducing the negative effects of alcohol (Patrick et al., 2018) and “cross-fading motives” (e.g., to get high by using both alcohol and cannabis) have been identified as unique motives for simultaneous use (Patrick et al., 2018; Patrick et al., 2020). A recent ecological momentary assessment study by Patrick et al. (2020) examined general substance use motives and cross-fading motives for simultaneous use. Cross-fading motives were assessed by averaging three items including “to be cross-faded”, “to increase the positive effects I get from alcohol”, and to “increase the positive effects I get from marijuana”. Having stronger cross-fading motives above and beyond general motives were associated with greater alcohol use and more positive alcohol consequences on simultaneous use days. However, approximately one fourth of simultaneous use days were not associated with deliberate cross-fading motives, suggesting other potential unique reasons for simultaneous use. It is likely that in some cases, someone is not necessarily seeking a specific outcome, but instead engages in simultaneous use as a more “reactive” process (e.g., because it is offered). Additional research is needed to continue to identify reasons why young adults decide to simultaneously use alcohol and cannabis.

Evaluations of Simultaneous Use Events

According to social learning theory, individuals’ behavioral decisions are based on experience, observation, and related cognitions (Maisto et al., 1999). Thus, the positive (e.g., meeting a new friend) and/or negative experiences (e.g., feeling nauseous) people have while drinking and/or using cannabis presumably will influence their subjective evaluation of that particular substance use event (i.e., how positive versus negative the experience was), and these evaluations may in turn influence future decisions about alcohol and cannabis use (Fairlie et al., 2016). While no studies have examined how people subjectively evaluate their simultaneous use events, studies have found overall evaluations of alcohol events (Fairlie et al., 2016) and evaluations of alcohol-specific consequences predict future drinking behavior (Barnett et al., 2015; Merrill et al., 2013). Exploring how individuals evaluate their simultaneous use experiences, and how they are perceived compared to single substance use experiences, may provide insight into the punishing and/or reinforcing properties of simultaneous use.

Patterns of Simultaneous Use

The act of using alcohol and cannabis together so their effects overlap makes simultaneous use a unique and complex substance use behavior. It is possible that the order of use (alcohol vs cannabis first) or relative quantities of use (e.g., a lot of alcohol and little cannabis vs a lot of cannabis and little alcohol) differentially predict outcomes, but little is known in this regard. Although there is robust laboratory literature examining the multiplicative effects of alcohol and cannabis on subjective intoxication (Downey et al., 2013; Hartman et al., 2015, 2016; Lukas et al., 1992; Lukas & Orozco, 2001; Perez-Reyes et al., 1988), only one study has examined the effects of use of one substance on subsequent use of the other (Chait & Perry, 1992). This study found that moderate doses of alcohol did not influence subsequent cannabis self-administration. No other studies to our knowledge have examined patterns of use in the laboratory.

Two non-laboratory studies to date have examined order of substances used during simultaneous use occasions. Barrett et al. (2006) found college students were more likely to use alcohol prior to cannabis on occasions when both substances were used. That being said, this study examined order of only the last simultaneous use event for each student and, therefore, findings did not necessarily reflect typical patterns of use and within-person variability was not examined. Gunn et al. (2020) found among young adults that days when cannabis was used first were characterized by lower alcohol consumption, but greater cannabis use on that day. Of note, this study examined co-use of alcohol and cannabis at the daily level, which resulted in inclusion of some days with larger time periods between alcohol and cannabis use not considered to be simultaneous use. Further research is needed to explore simultaneous use patterns within a specific event, including timing of substance use during individual simultaneous use events. Additionally, these studies fail to provide insight into when and why people use in certain orders or patterns. Particular patterns of use may both be differentially predicted (e.g., by context, motives) and differentially associated with consequences of simultaneous use. As such, continued research on patterns of simultaneous use could have important intervention implications.

Qualitative Methods to Understand Simultaneous Use

Our understanding of simultaneous use among young adult populations is still in a nascent stage making qualitative methods (e.g., individual interviews, focus groups) particularly useful for understanding this simultaneous use phenomenon. Such methods can provide specific first-hand accounts of how, why, and under what conditions simultaneous use occurs (Miles & Huberman, 1994). Qualitative methods have been used as formative work for quantitative studies of simultaneous use behavior among young adults (i.e., cited but findings not published) (Patrick et al., 2018), and to explore contextual influences of simultaneous use among adolescents in a single published qualitative paper (Price Wolf et al., 2019). Price Wolf et al. (2019) found among youth that decisions about whether to engage in simultaneous use were context specific and simultaneous alcohol and cannabis use was described as occurring in both destination (e.g., contexts where a significant amount of time was spent) and transitional (e.g., contexts where youth were on their way to somewhere else, such as in a car) contexts. However, a detailed qualitative analysis of why young adults engage in simultaneous use, how they subjectively evaluate simultaneous use events, or patterns of use has yet to be conducted. Such work can be particularly useful for the generation of hypotheses to be tested in subsequent quantitative studies.

The Present Study

The goal of the present study was to gain insight into college students’ recent simultaneous use events in order to inform future studies of simultaneous use. We hope the findings of this study can inform the development of simultaneous use measures/assessments and generate hypotheses about factors that influence simultaneous use that can be further studied via quantitative methods. We sought to extend prior research by conducting individual interviews on simultaneous use experiences among heavy drinking college students. The specific focus of this qualitative study was to better understand reasons for simultaneous use, evaluations of simultaneous use, and common patterns of substances used during simultaneous use events.

Methods

Participants

One hundred heavy drinking young adults participated in 28-days of ecological momentary assessments (EMA) and a follow-up interview. This study included 38 young adults who were interviewed about simultaneous use experiences at the post-EMA follow-up. Eligibility criteria included being age 18–20, enrollment in a 4-year college, ownership of a smartphone with a data plan, and either (i) consumption of 4+ (women)/5+ (men) drinks in a single occasion at least weekly or (ii) experience of at least 1 out of 10 negative alcohol-related consequences assessed (e.g., hangover, blackout) in the past two weeks. Ineligibility criteria included illicit drug use (other than cannabis) in the past two weeks or current treatment for a substance use disorder. Young adults were recruited in 2017 from one northeast U.S. college located in a state where medical cannabis use was legal and recreational cannabis use was decriminalized but not legal at the time of data collection. Demographics and substance use behavior of the sample are reported in Table 1.

Table 1.

Participant Demographics and Substance Use Behavior (n=38)

	N/% OR MEAN (SD)
Age	18.7 (0.66)
Biological sex a
Male	19 (50%)
Female	19 (50%)
Year in school
Freshman	31 (82%)
Sophomore	7 (18%)
Race (check all that apply)
White	27 (71%)
African American	2 (5%)
Asian	8 (21%)
Native American/Alaskan	1 (3%)
Hawaiian/Pacific Islander	1 (3%)
Other	4 (11%)
Ethnicity
Hispanic/Latinob	9 (24%)
Substance use behavior (reported across 28 daily morning reports)
Cannabis use days	5.00 (5.33)
Drinking daysb	5.58 (2.39)
Heavy drinking days	3.76 (2.12)
Simultaneous use daysc	1.94 (1.53)
Baseline drinking behavior
Drinks per week	10.81 (5.94)
Drinks per drinking day	4.83 (2.32)

^aGender identity was asked in addition to biological sex. Gender identity corresponded with biological sex for all participants except for one individual who reported biological sex as male and reported gender identity as trans female and one individual who reported biological sex as female and indicated that they preferred not to report their gender identity.

^bThe 38 college students interviewed about their simultaneous use were more likely to identify as Hispanic or Latino X²(1, N=100) =4.774), p=.029 [9 (24%) vs. 5 (8%)] and reported more drinking days during the 28-day EMA period t(98) = 2.030, p=.045 [5.58 (2.39) vs. 4.44 (2.92) drinking days] than the other college students in the EMA study. No other demographic or drinking behavior measures were found to differ between these students.

^cBased on n=35 (of 43) who endorsed simultaneous alcohol and cannabis use during the EMA study and were also interviewed about simultaneous use. The majority of these participants (n=22 out of 35) reported a single simultaneous use event during the 28-day EMA period.

Procedures and Measures

Recruitment and Enrollment

All procedures were reviewed and approved by the University Institutional Review Board. Flyers and social media advertising were used for recruitment. Interested volunteers completed an online screener and those eligible viewed an online consent form. After consenting, participants were directed to complete a baseline survey. Participants who completed the baseline survey then signed up for one of several in-person group orientation sessions, where they consented to remaining study procedures.

Baseline Survey

Demographics assessed at baseline included age, sex, gender identity, ethnicity, year in school, and race. Participants completed the Daily Drinking Questionnaire (Collins et al., 1985) estimating the number of drinks they typically consumed each day of the week in the past 30 days. These data were summed across days to determine drinks per week, and averaged across drinking days to determine drinks per drinking day.

Orientation and EMA Protocol

Participants attended one of several in-person group orientation sessions to learn about study procedures and at orientation they consented to the EMA and follow-up interview. During the EMA period, surveys were sent directly to participants’ mobile phones through an application (programmed via MetricWire Inc.). Relevant to the present study, a daily morning report included the questions, “Did you use marijuana yesterday?” and “Did you drink yesterday?” If a participant endorsed both cannabis and alcohol use, they were also asked, “Were you under the influence of both marijuana and alcohol at the same time yesterday?” For additional information on the EMA protocol see (Merrill & Aston, 2020; Merrill et al., 2019).

Follow-up Interview

All participants completed an individual interview on average 10 days (SD = 6.88) after completion of EMA. At the interview session a timeline follow-back (TLFB) interview assessing alcohol use and consequences was completed for the same 28-day period over which the participants had completed the EMA. Thirty-eight college students who reported simultaneous use during the EMA, the TLFB, and/or elsewhere in the interview were asked about their recent simultaneous use experiences¹. Key simultaneous use questions asked during the interview included: (1) “What were your reasons or motivations for using both alcohol and marijuana together?”; (2) “On times when you mix alcohol and marijuana, what substance do you use first, and when do you use in the other order?”; and (3) “If you were to compare nights when you used only alcohol to nights when you used both alcohol and marijuana together, in what ways would you say your perception or evaluation of those nights differ?” Interviewers were trained to probe for additional details upon initial responses to an interview question.

Thematic Analysis

Interview audio files were transcribed verbatim. The six-phase thematic analysis approach by Braun and Clarke (2006) was followed to code and analyze the interview data. First, the first author (HKB) created initial codes for the codebook based on the structured interview guide and through reviewing transcripts. Second, the first author and three additional authors (HKB, RLG, OSF, and GL) independently coded transcripts, and additional preliminary codes were developed from the data and defined based on the objectives of the study. The coding team discussed codes until a consensus was reached, and the coding structure was further refined during this early stage of analysis. Each transcript was ultimately coded by two team members, who then met to discuss differences and resolve discrepancies, bringing the final coding for all 38 transcripts to 100% agreement. Final codes were entered into NVivo12 (QSR International, 2018). In the third phase, the coded transcripts were analyzed by creating written summaries of the codes to describe the most commonly reported experiences. Next, for the fourth phase, themes and sub-themes from the codes were identified and refined. These themes were reviewed through ongoing dialogue with others on the research team to ensure they were grounded in the original data. Fifth, the themes and subthemes were finalized and defined. Lastly, a selection of quotes from each theme and subtheme were selected and presented here. A sample size of 38 interviews is characteristic of what is often seen in exploratory qualitative work with a homogenous sample (Vasileiou et al., 2018). Thematic results are described below and presented in Table 2.

Table 2.

Participants’ Reasons for Simultaneous Use, Evaluations of Simultaneous Use, and Patterns of Use

REASONS FOR SIMULTANEOUS USE
1. Cooper’s 4-Factor Model
Social (n=11)	“There are some drinking nights where like I would just sort of go to bed, but then other nights where people would be up until maybe three o’clock. If that was the case, then I would probably decide to smoke. I would say it’s definitely social for me.” -1043 (female) “Mixing it with drinking, like the right amount, to want to be social and want to go out and do stuff, but not to the extent to where I’m making bad decisions.” -1022 (male)
Enhancement (n=16)	“Uh probably to make the day/night more fun.” -1009 (female) “I usually drink and like if I smoke it’s with people that I’m close to so there is never peer pressure. I just do it cause I want to and cause it will be more fun and cause I want to because it seems like a thing that will make me feel good somehow.” -1021 (female)
Conformity (n=11)	“At that rush event that I described, it was just the social conformity scenario. I think because other people were drinking and smoking I was interested as well.” -1025 (male) “Um usually if it was friends who were mixing I’d just like join in. It was usually because friends were doing it” -1072 (female)
Coping (n=7)	“I would say that most of the time I would end up using marijuana after I was done drinking and the time period between my last drink and the marijuana was very short. My motivation for using marijuana was usually just to calm down from being just like upset.” -1043 (female) “If I was like really trying to get out of my head I guess I would say deciding to combine them is definitely more effective than using one or the other. It kind of feels like I’m, um more out of it or I guess I just feel the psychoactive properties. It’s like a lot more concentrated basically and I would say usually I am in a pretty good mood for the duration of the effects when I use both.” -1096 (male)
2. Harm Reduction Motives (n=15)	“I smoke so I don’t have to drink as much. It’s nice to have maybe three drinks over a couple of hours and then feel good for the night, instead of having like seven.” -1027 (female) “One of the reasons I’ve done that before is kind of like to reduce the possibility of having a hangover. I feel like I can usually drink less and kind of arrive to the same state of being or desired destination or whatever if I do smoke as well.” -1096 (male) “I use weed to mitigate the negative effects of alcohol. A lot of times when I just drink like I’m not as coordinated and I might get like a small headache in the morning or something like that and feel kinda lethargic the next day. I’ve found that all the times when I combine both I sleep better, I don’t wake up with a hangover, and I feel like a lot more in control in terms of my motor abilities.” -1048 (female)
3. Cross-faded Motives (n=6)	“Um, together I did it to bring my high to like the next level.” -1022 (male) “I would say the main reason is like marijuana is very helpful. When you mix it with alcohol it makes you feel more relaxed and at the same time you still get the positive like energetic effects of alcohol. It’s an interesting mix.” -1074 (trans female)
4. Reactive/Situational Reasons
Using Cannabis During a Drinking Event Because Intoxicated (n=11)	“Yeah it was just a matter of like “Oh why not!” I didn’t really like think it through, I think cause, I was already nine drinks in or something like that.” -1015 (male) “I made the decision to smoke marijuana, which isn’t a very good decision for me. A significant part of that was because I was drunk and making decisions less well.” -1080 (female) “Um, also sometimes people are smoking and if you’re drinking then I feel like you’re more likely to say “Oh yeah, I’ll smoke too.” -1111 (female)
Using Cannabis During a Drinking Event Because Available/Offered (n=17)	“Normally I smoke after drinking just because it’s there and I’m like “Oh I guess I wouldn’t mind doing that right now.” -1070 (female) “Yeah um I feel like I don’t ever seek out marijuana when I drink, it’s just I only use it when people will offer it.” -1102 (female) “Weed has a much more presence on this campus. It’s like very accessible and I think I wasn’t craving it; it was just there so I smoked and drank.” -1011 (male)
EVALUATION OF SIMULTANEOUS USE EVENTS
1. Depends on Patterns of Use (n=10)	“Usually when it’s dying down and once I’ve like stopped drinking, then they’ll pull it out and we smoke. I don’t evaluate this as different then a night I just drink.” -1102 (female) “Recreationally I would probably say alcohol only, marijuana only, and then both as last. But times when I smoke at the end of the night after drinking I would say that is similar to alcohol only times.” -1005 (male)
2. Depends on Positive and Negative Consequences Experienced (n=22)	“So I would say the nights where I have both are better. I feel better, I sleep better, I don’t wake up feeling like lethargic. I can get my schoolwork done without feeling tired, it’s a nicer feeling I feel more in control.” -1048 (female) “Well it’s an interesting and very different reality, cause your reality changes depending on what substance your using. I think I am pretty familiar with the feeling of the altered reality while drinking to some extent as the reality isn’t always so altered, but with marijuana it’s been changing for me recently. Like triggering fear and making me sick so cause of these times that really makes me not want to mix. I think the experience of being under both alcohol and marijuana can be more negative for me than just being under alcohol, but it depends.” -1080 (female)
3. Depends on Internal and External Context (n=20)	“If you’re going out like to gross parties that are like really packed, I usually don’t smoke because I don’t feel comfortable smoking around people I don’t know. I would evaluate that as negative. But I would drink.” -1111 (female) “So I would say when I just drink that would be more appropriate for if I’m going to like a frat party, or just some kind of larger on-campus party or socializing with a lot of people I don’t know. If I mixed for that scene that would be bad cause I might be out of control. I would mix the two most of the time with some friends and if it wasn’t like we had to do a lot afterward I would evaluate mixing there as positive.” -1096 (male)
PATTERNS OF SIMULTANEOUS USE
1. Order of Use (n=22)	“Given that I felt physically sick versus other nights when smoking after drinking, I avoid that order. I don’t typically, it’s not common for me to feel physically sick at the end of the night.” -1042 (male) “I would say that most of the time I would end up using marijuana after I was done drinking” -1043 (female)
2. Quantities of Substances Used (n=16)	“Um, I felt I didn’t have to drink as much to feel the effects because there were the effects of marijuana.” -1009 (female) “That night it was a little more blended, but like I drank the drink slower over time. I drank less and I didn’t smoke as much. So it was like I try to balance.” -1027 (female) “If I am having a lot of alcohol I’ll only smoke like a small one hit, maybe two hits that are like small, or if I’m pretty high I’ll have only one drink.” -1044 (male)
3. Timing of Substance Use (n=14)	“I usually like once I start smoking I stop drinking. There are only a couple of nights where I kept going because I wasn’t drinking a lot.” -1027 (female) “Well it was kinda more of just a chill night and so three shots doesn’t really hit me that hard so I did it an hour or so after I drank. Then we were all just chilling in the lounge and I was like yeah, and somebody asked so we all just smoked.” -1087 (male)

Results

Reasons for Simultaneous Use

Heavy drinking college students’ reasons for simultaneous use fell into four different categories: (1) those consistent with Cooper’s 4-factor motives (i.e., social, conformity, enhancement, and coping motives) (Cooper, 1994), (2) harm reduction motives, (3) cross-fading motives (Patrick et al., 2020; Patrick & Lee, 2018), and (4) reactive/situational reasons. Each is detailed below.

Participants indicated motives for simultaneous use that included all four categories of Cooper’s motivational model (Cooper, 1994). For example, some students reported simultaneous use to decrease negative mood (i.e., coping motive). Participants reported using cannabis during a drinking event because there was peer pressure and did so in order to fit in (i.e., conformity motive). Participants also reported simultaneous use to be more social (i.e., social motive) and to increase positive mood and have more fun (i.e., enhancement motive). One male participant (ID 1065) reported enhancement motives for simultaneous use stating:

So generally, my reasoning was to make the night more fun or exciting. Um, more or less I could laugh more easily with people who were also under the same kind of influence of alcohol and marijuana. Basically, I can feel very relaxed really.

Many participants reported simultaneous use for harm reduction reasons and were focused particularly on reducing the negative effects of alcohol. In particular, these heavy drinking college students reported harm reduction, or drinking less, as a motive for using cannabis simultaneously with alcohol. They also mentioned use of cannabis during a drinking event to reduce undesirable effects of alcohol such as engaging in simultaneous use to reduce a hangover the next day. For example one male participant (ID 1060) stated:

I’ll drink, get drunk, um go home and be a little bit less drunk, and then when I am ready to go to sleep, I’ll smoke just to ease the hangover the next morning or something.

Some heavy drinking college students in our sample reported mixing alcohol and cannabis for “cross-fading” reasons. They reported engaging in simultaneous use to feel both high and intoxicated. As one male participant (ID 1007) said:

Uh mostly the effects to me are really good complements for each other cause alcohol is great, it’s great for going to parties. It’s a social lubricant. It makes you loose, makes you want to dance more, and talk to people and things like that, but weed sort of makes you more happy, more kind of laid back.

Data derived from our questioning about reasons for use also revealed that sometimes simultaneous use was not necessarily motivated by a desire to achieve a particular goal. Rather, it often occurred in a more reactive manner, in response to one’s environment. There were two unique types of reactive motives described. First, participants mentioned not planning to use cannabis during a drinking event, but doing so simply because it was available and offered to them. Second, participants reported that being more intoxicated made them more open to the idea of subsequently using cannabis. They often stated that they decided to use cannabis because they were not able to think through this decision while intoxicated or were not able to consider possible negative consequences of simultaneous use. As one female participant states (ID 1054):

Um, when I’m drunk, I feel like I am just like more open to [using cannabis] and if someone’s gonna offer it to me, I’m just gonna take it.

Evaluation of Simultaneous Use Events Compared to Single Substance Use Events

There was variability in how participants subjectively evaluated their simultaneous use events compared to single substance use events. Some had no preference, some preferred simultaneous use, and (despite that all participants had engaged in simultaneous use) some preferred single substance use events. The qualitative data revealed that subjective evaluations of how positive or negative a simultaneous use event was (compared to single substance use events) not only differed across people, but also was not consistent across events (within-person). Rather, it depended on patterns of use, negative and positive consequences experienced during simultaneous use, and external and internal context. In terms of patterns of use, heavy drinking college students reported that in the event that they used cannabis at the end of a drinking event just prior to bed, their perception of simultaneous use events ended up being similar to alcohol only events. One male participant’s (ID 1003) response to whether their evaluation of simultaneous use events differs compared to single substance use events was:

No, because I am not usually doing anything or interacting with many people on the nights after I have mixed them. So, it’s usually like smoke, hang out for a bit, then go to bed so I don’t have any change in perception.

Participants also discussed how their evaluations of simultaneous use events were influenced by previous negative or positive consequences experienced during simultaneous use. Participants who reported a preference for simultaneous use events reported enjoying simultaneous use events more because they drank less during these events, felt more in control, and slept better compared to single substance use events. Those who reported preferring single substance use compared to simultaneous use events reported experiencing negative cognitive and physical consequences as a result of simultaneous use. These college students reported more cognitive impairment on simultaneous use events (i.e., feeling dizzy, more intoxicated) and reported feeling nauseous and vomiting when engaging in simultaneous use. For example one female participant (ID 1026) said:

If I were to choose, I probably would not try to use them both at the same time again any time soon. I did not like the feeling dizzy part and just trying to walk around and feeling like I was going to fall over. I did not like that at all and the other times when I was drinking heavily, I didn’t feel that at all, so right now I like drinking nights more.

A number of participants reported that evaluations of substance use events were event-specific and dependent on internal (e.g., mood) and external (e.g., location or event type) context. Participants often reported feeling more comfortable engaging in simultaneous use in private locations and with close friends and evaluated occasions of simultaneous use in these contexts as more positive. College students reported that their evaluation of simultaneous use events was dependent not only on the external context but also on their pre-simultaneous mood, the mood or subjective effects they were hoping to experience that night, and whether those effects were achieved. For example, participants reported more positive evaluations of simultaneous use events on occasions when the goal of the night was to relax and chill out and mixing alcohol and cannabis was able to help them achieve that. For example one transgender female participant (ID 1074) who discussed getting “crossed” (i.e., engaging in simultaneous alcohol and cannabis use) stated:

I think the main difference just comes in the fact that when I’m crossed, I usually want to be just like chilling out in someone’s dorm as opposed to going to an event or a party or like walking around, so it’s more the experience that is different than the actual evaluation. It depends what I am looking for that night. A night I want to chill and relax is a good night when I get crossed.

Patterns of Use

When sharing their simultaneous use experiences, college students discussed their patterns of use including: (1) order of substances, (2) timing of substance use, and (3) quantities of substances used. There was variability in the order of substances used during simultaneous use events, and this appeared to depend on context and/or one’s desirable (or undesirable) simultaneous use outcomes. College students who reported drinking first during simultaneous use events often reported using cannabis after they were back in a private setting (i.e., their house or a friend’s house) and many reported using cannabis just prior to bed. Additionally, many participants stated that they used alcohol and cannabis in a particular order in hopes of avoiding negative consequences, but this order varied between people. They often mentioned negative consequences they had previously experienced when engaging in simultaneous use in the opposite order. For example one male participant (ID 1020) said:

I usually smoke before I drink because every time I drink and then I smoke I throw up, so smoking and then drinking, and in that order. I’ve never really had such a bad experience where I’m crossed unless it was where I drank first and then smoked.

Participants also reported on timing of substances used during simultaneous use events. They reported often waiting a period of time between when last using one substance before using the other substance (yet still reporting that their effects overlap). Many young adults reported that they would stop drinking once they started using cannabis on simultaneous use occasions. They reported that a sequence of substance use where one substance is finished prior to the start of the next substance helped to decrease the likelihood of experiencing adverse (or increase the likelihood of positive) effects from simultaneous use. For example one male participant (ID 1060) stated:

I don’t know, whenever I use both, it’s always kind of staggered. So my night out is always just alcohol and when I get back it’s like then I smoke a little bit. It’s kind of nicer to be just a little bit drunk and a little bit high.

With respect to quantity of each substance used during simultaneous use events, participants reported using less alcohol and/or cannabis on occasions when they used both substances together compared to single substance use events (alcohol-only, cannabis-only). Individuals mentioned being cautious about consumption levels of alcohol and cannabis during simultaneous use events. They reported not needing to use as much of a single substance to achieve desired levels of intoxication/high and using less alcohol and/or cannabis during simultaneous use to avoid negative consequences. As one male participant (ID 1096) indicated:

I’m a lot more cautious, I would say, when I combine them, about how much I drink, cause I used to drink the amount I would have if I was only drinking alcohol and sometimes also smoke and that would usually result in me vomiting or like having memory loss. So, yeah, now I try to limit the amount of alcohol I have or like space it out more.

Discussion

This qualitative study provides detailed and novel insight into simultaneous use experiences of heavy drinking college students. Broadly, salient themes that emerged included that college students have both intentional and situational/reactive reasons for simultaneous use; evaluation of simultaneous use events depends on patterns of use, context, and consequences experienced; and patterns of use vary across order, sequence, and quantities of substances used during simultaneous use occasions. Each of these themes and corresponding subthemes are discussed in more detail below.

Reasons for Simultaneous Use

We found heavy drinking college students engage in simultaneous use for motives that fall into the four factors outlined by Cooper (1994) for single substance use including social, coping, enhancement, and conformity motives. While these motives have traditionally been endorsed when examining single substance use, the college students we interviewed often made it clear that the behavior and/or effects of mixing alcohol and cannabis influenced later motivations to engage in simultaneous use across these four factors. For example, young adults often reported mixing alcohol and cannabis to have “more fun” and/or “feel more relaxed” (enhancement motives). Although few participants reported engaging in simultaneous use to cope, those that did described simultaneous use as more effective for coping than single substance use. College students in our sample reported engaging in simultaneous use because others were drinking and using cannabis and some reported using cannabis at the end of the drinking event to continue to feel sociable and to keep socializing longer. These findings suggest that these reasons for simultaneous use may be more than just a reflection of the desired effects of each individual substance; instead, college students may engage in simultaneous use for social, conformity, enhancement, and coping motives because of effects that may be specific to the combination of alcohol and cannabis.

However, college students also reported motives unique to simultaneous use (i.e., those that cannot be relevant for just one substance or the other), including harm reduction motives (e.g., using cannabis during a drinking event in order to drink less) and cross-fading motives. These unique simultaneous use motives correspond respectively to substitution and complementary reasons for simultaneous use. The complementary hypothesis refers to the effects of one substance being enhanced by the use of the other. In this case, using cannabis at the same time as alcohol may lead individuals to drink more to continue or increase positive subjective effects. The substitution hypothesis refers to the idea that one substance can pharmacologically replace the other. In this case, drinkers may drink less when they use cannabis (Subbaraman, 2016). Of note, unlike prior work that only measured the general harm reduction motive “to reduce the negative effects of alcohol” (Patrick et al., 2018), participants in our study described specific harm reduction motives including engaging in simultaneous use to reduce alcohol consumption and to reduce a hangover.

Consistent with recent reviews (Risso et al., 2020; Schlienz & Lee, 2018), our sample more often reported substitution (harm reduction motives) versus complementary (cross-fading motives) reasons for simultaneous use, with many students reporting that they intentionally used cannabis before or during a drinking event in order to drink less or to reduce the negative effects of alcohol. Thus, interventions may need to educate students on the fact that even if simultaneous use results in less drinking or less of a hangover, it may have numerous other negative impacts. There was less discussion among our participants about engaging in simultaneous use for cross-fading or complementary reasons. This contrasts with quantitative studies reporting that young adults recognize cross-fading motives as unique motives for simultaneous use and frequently endorse cross-fading motives (Patrick et al., 2019; Patrick et al., 2020). This may be due to the specifics of our sample, which was characterized by heavy drinking college students, the majority of whom reported infrequent simultaneous use (i.e., less than two simultaneous use occasions on average in the past 28 days). Further research identifying subgroups prone to using alcohol and cannabis for cross-fading reasons is needed as cross-fading motives have been associated with greater alcohol use and intoxication on simultaneous use days (Patrick et al., 2020).

In addition to intentional reasons for simultaneous use, college students also reported reasons for simultaneous use that were less intentional, and more reactive to situational factors surrounding use. Participants often reported using cannabis because they were already intoxicated, and were unable to think through their decision and consider potential resulting consequences of simultaneous use. The alcohol myopia theory suggests that excessive alcohol use can impair inhibition and lead to riskier decision-making (Steele & Josephs, 1990). Drinking heavily may lead individuals to allocate their attentional resources to the most salient, proximal stimuli (e.g., using cannabis when people around them are using), underestimating later risks (e.g., getting sick or risk of driving under the influence). Our qualitative findings suggest that alcohol myopia may be one underlying mechanism for simultaneous use (at least on some occasions) among heavy drinking college students. Though the research is mixed, multiple studies have shown that simultaneous use and alcohol-only days do not differ in terms of negative consequences when controlling for amount of alcohol consumed (Gunn et al., 2020; Lee et al., 2020; Mallett et al., 2019; Sokolovsky et al., 2020). This suggests that alcohol use may drive negative consequences and harms on simultaneous use occasions and thus situations where college students decide to use cannabis because they are already highly intoxicated may be particularly risky.

Additional situational reasons for simultaneous use included availability of cannabis and peers offering cannabis during a drinking event. These situational influences led to in-the-moment decisions to engage in simultaneous use. Additionally, alcohol intoxication level and availability/offers may intersect such that on occasions when alcohol is used first, the disinhibiting effect of alcohol may lead young adults to more likely use cannabis when available and/or offered. Future work is needed to assess whether it is alcohol’s disinhibiting effects in particular that increase the likelihood of simultaneous use among young adults.

Evaluation of Simultaneous Use Events

Heavy drinking college students in our sample reported that evaluations of simultaneous use events depended on patterns of use, positive and negative consequences experienced, and internal and external context. Some students mentioned evaluations of simultaneous use vs. alcohol-only events were similar because they did not use cannabis until the end of a drinking event, just prior to going to bed. Thus, pointing out that these substance use occasions that ended up being simultaneous use consisted primarily of being under the influence of alcohol only. While studies have begun to examine patterns of use, these studies have focused on order of substance use (Barrett et al., 2006; Chait & Perry, 1992; Gunn et al., 2020) during simultaneous use or co-use occasions, and not on timing of use. Likewise, many event-level analyses of simultaneous use have been at the daily level and thus do not account for differences in timing of simultaneous use, such as mixing alcohol and cannabis at the beginning versus the end of the event (Lee et al., 2020; Linden-Carmichael et al., 2020; Lipperman-Kreda et al., 2017; Mallett et al., 2019). Studies where consequences differ between simultaneous use occasions and alcohol-only occasions may include individuals who often engage in simultaneous use earlier during a substance use occasion, making simultaneous use occasions distinct from alcohol-only occasions. On the other hand, studies where consequences did not differ between simultaneous use occasions and alcohol-only occasions may include individuals who predominately engage in simultaneous use towards the end of a substance use event, making simultaneous use occasions less distinguishable from alcohol-only occasions.

College students also spoke about evaluations of simultaneous use in relation to positive and negative consequences experienced during simultaneous use events. Social learning theory posits observation, experience, and cognitions (e.g., expectancies, interpretations) can influence future behavior (Maisto et al., 1999). Accordingly, consequences experienced during simultaneous use and evaluations of simultaneous use events may influence future simultaneous use. College students referred to positive consequences experienced during simultaneous use as reasons why they prefer simultaneous use events over single substance use occasions. On the other hand, evaluations that simultaneous use in general or specific simultaneous use events were more negative than single substance use events were often based on college students experiencing negative consequences during simultaneous use occasions. Based on previous alcohol research, evaluations of substance use consequences experienced can directly influence evaluation of substance use events and future substance use (Fairlie et al., 2016).

College students also reported that their evaluations of simultaneous use events depended on both external (e.g., location and/or event-types) and internal (e.g., mood) context. Students reported more positive evaluations of simultaneous use occasions when simultaneous use occurred in private settings that were relaxing and calm with close friends. They felt more comfortable engaging in simultaneous use in these locations and their evaluations reflected this. Students viewed alcohol-only use as more favorable for parties and large events that were more intense and with people they may not know, and evaluated simultaneous use in these party settings as more negative. These findings, that evaluations are dependent on context, align with prior research (Merrill et al., 2018) and social learning theory (SLT), which highlights the idea of differential reinforcements. In other words, simultaneous use events may be evaluated differently depending on contextual factors, both internal and external.

Patterns of Use

As described above, motives may result in the selection of a particular simultaneous use pattern, and evaluations of simultaneous use may depend on the selected pattern of use. Our analysis revealed that college students may intentionally engage in particular patterns of use to avoid negative consequences. In other words, these patterns of use were often described as strategies college students used to avoid negative consequences or harm during simultaneous use events. These strategies included: (1) using cannabis after a drinking event when they were in a private space where they felt comfortable and safe, often prior to going to bed, (2) spacing out the use of the two substances (yet still using the two substances so effects overlap) and often finishing using one type of substance before beginning the second, and (3) using less of one or both substances during simultaneous use events.

While studies have examined harm reduction strategies related to single substance use topography (e.g., pace, amount), no studies have examined harm reduction strategies used during simultaneous use. For example, harm reduction strategies related to topography of drinking (e.g., avoiding drinking games, not doing shots, not drinking fast) are strongly associated with reduction in alcohol consumption and negative alcohol-related consequences (Linden-Carmichael et al., 2018; Martens et al., 2007; Napper et al., 2014; Pearson et al., 2013). One study found that use of alcohol- and cannabis-specific protective behavioral strategies reduced alcohol/cannabis-related harms among co-users (Bravo et al., 2019). Thus, future studies should examine harm reduction strategies of simultaneous use, particularly those surrounding patterns of use.

Limitations

It is important to note the limitations of this study. First, our sample consisted only of heavy drinking college students, age 18–20, the majority who were White (71%), and who reported an average of about two simultaneous use occasions over 28 days. Thus, the generalizability of these findings may be limited, and should not be used to characterize more frequent simultaneous users, more moderate drinkers, non-college students, or more racially/ethnically diverse individuals. Second, unfortunately, we did not collect data on cannabis and simultaneous use history, despite the potential impact that one’s prior level of experience with these behaviors could impact their reasons for use or subjective evaluations of simultaneous use events. For example, infrequent or first-time simultaneous users may have more negative experiences with simultaneous use compared to those who have chosen to engage in the behavior repeatedly over time. Third, during the interviews, participants often discussed simultaneous use events that occurred during the 28-day EMA period. It is possible that assessment reactivity during EMA may have influenced the salience of and participants’ subjective perceptions of these simultaneous use events. However, the interviews did not strictly focus on simultaneous use events that occurred during the EMA period; young adults often shared their general experiences of past simultaneous use. Fourth, our study focused on simultaneous use, but did not examine use of other drugs that may be associated with additional risk. Future studies should examine how simultaneous use overlaps with other drug use and consequences that result from poly-drug use. Finally, our findings are based on self-reported data, which could be prone to social desirability and recall bias and did not include direct observation of substance use behaviors. Nonetheless, our qualitative data on recent experiences provide detailed information that cannot be captured via other methods, and suggest several avenues for future research.

Implications of Findings for Future Work

A primary goal of this study was to inform the development of simultaneous use assessment/measures and generate hypotheses about factors that influence simultaneous use that can be further studied via quantitative methods. These findings have several important implications for future studies. Much of the research on reasons for simultaneous use has focused on traditional goal-directed motives, but our findings suggest that research may also benefit from including more measures of reactive/situational factors that may lead college students to use cannabis during a drinking event, such as level of personal intoxication and availability. Conducting event-level simultaneous use studies via EMA would allow intentional reasons for simultaneous use to be examined prior to simultaneous use events and situational/reactive reasons to be examined following simultaneous use events, and to determine which type of motives are associated with more negative outcomes of simultaneous use.

While a few quantitative studies have examined motives unique to simultaneous use, such as “cross-fading motives” (Patrick et al., 2018; Patrick et al., 2020) and reducing the negative effects of alcohol (Patrick et al., 2018), the harm reduction motive revealed here “using cannabis during a drinking event in order to drink less” has not been previously studied as a motive for simultaneous use. This motive was often endorsed among this sample of heavy drinking college students and should be included in future quantitative studies examining reasons for simultaneous use. For example, such studies could examine in what context (e.g., large party settings with strangers) college students use cannabis during a drinking event with the goal of drinking less, and whether this unique simultaneous use motive, relative other motives, is associated with fewer consequences. Future studies should also assess intentions for limiting alcohol and cannabis consumption during simultaneous use events relative to single substance use events (alcohol-only, cannabis-only occasions).

Interestingly, this sample of college students endorsed harm reduction motives related to reducing alcohol use and corresponding negative effects, but not related to reducing cannabis use, which may be due to the fact that they were all heavy drinkers. It is possible that simultaneous use and its motives among heavy cannabis users (e.g., daily users) are very different than those of heavy drinkers. Future studies should characterize simultaneous use events for young adult populations who vary in terms of both their drinking and cannabis use levels. For example, such work could examine whether heavy cannabis users report engaging in simultaneous use in order to use less cannabis during a substance use event.

While college students reported simultaneous use occasions where they used cannabis during a drinking event in order to drink less, they also report occasions where they used cannabis because they were already highly intoxicated from alcohol. They indicated that alcohol intoxication made them more open to using cannabis. As mentioned above, alcohol myopia may be a potential mechanism for simultaneous use. Thus, future studies should assess intoxication levels of young adults throughout a substance use event and determine whether higher levels of intoxication predict simultaneous use in real-time. Based on these qualitative findings, we might hypothesize that simultaneous use is more common when a substance use event begins with alcohol versus cannabis, at least among heavy drinkers.

Findings also highlight the need to more closely examine how certain patterns of substance use may influence evaluations of simultaneous use events and their negative outcomes. While a few studies have examined initial order of substance use (i.e., using alcohol versus cannabis first, Barrett et al., 2006; Chait & Perry, 1992; Gunn et al., 2020) during simultaneous use or co-use occasions, future studies could assess whether particular simultaneous use events are characterized by the use of one substance completely proceeding the other, whether other simultaneous use occasions involve a back-and-forth of using alcohol and cannabis, and which patterns are most problematic. Young adults reported sometimes only using cannabis during a drinking event at the end of the night, when still intoxicated but no longer drinking, and often right before bed. Events where simultaneous use occurs at the end of the night might be less risky (assuming one is home safe for the night) than simultaneous use occurring earlier in the evening. EMA methods could be used to examine the timing of use and corresponding consequences and evaluations.

This was the first study to examine subjective evaluations of simultaneous use events; findings indicated that evaluations of simultaneous use varied depending on previous consequence experiences, external context, and internal context. Future quantitative studies could assess evaluations of simultaneous use events closer in time to when they occur (e.g., the next day) and determine whether evaluations differ from event-to-event. If there are event-to-event differences in evaluations, next steps could be to examine what predicts these differences in evaluations and identify event-level consequences that are experienced. One might hypothesize that positive evaluations of recent simultaneous use events are reinforcing and result from experiencing positive consequences (while negative evaluations of simultaneous use are punishing and result from experiencing negative consequences) and that these perceptions of a given event may predict future simultaneous use.

Conclusions

Understanding reasons for simultaneous use, evaluation of simultaneous use occasions, and patterns of use deepens our understanding of simultaneous use behavior. Further understanding of reasons for simultaneous use and patterns of use may help to identify simultaneous use occasions that result in the greatest risks. Additionally, considering evaluations of consequences and simultaneous use events may elucidate the reinforcing and punishing aspects of simultaneous use and predict future behavior. Continuing research on these aspects of simultaneous use will help to inform interventions to target this high-risk behavior.

Public Health Significance.

This study highlights variations in reasons for simultaneous alcohol and cannabis use, evaluations for simultaneous use, and patterns of use. Understanding reasons and corresponding patterns of simultaneous use may help to identify risky simultaneous use occasions. Understanding evaluations of these occasions may help to predict future substance use behavior and inform prevention and intervention efforts aimed at reducing simultaneous use and associated harms.