A qualitative examination of positive and negative consequences young adults experience from simultaneous alcohol and cannabis use

Abstract

Objective:

Alcohol and cannabis are two of the most commonly used substances among young adults, and most individuals who use both substances use them simultaneously, that is, on the same occasion such that their effects overlap. Given the high prevalence of simultaneous alcohol and cannabis use, it is important to understand the relationship between simultaneous use and consequences. This study presents a qualitative examination of positive and negative consequences of simultaneous use.

Method:

We conducted individual interviews among 36 young adults who engage in simultaneous use (23 women, 12 men, 1 trans man). Interviews included open ended questions examining negative and positive consequences of simultaneous use and how simultaneous use differed from single substance use (alcohol only use, cannabis only use). Interviews were analyzed using applied thematic analysis.

Results:

Young adults reported numerous negative and positive consequences of simultaneous use, many overlapping with single substance use. Yet, they also reported unique combinations of positive consequences not experienced by single substance use. Young adults discussed patterns of use that were sometimes approached intentionally (e.g., quantity of substances used, order) that influenced consequences.

Conclusions:

Together these findings provide further insight into young adults’ simultaneous use experiences. Next steps should include quantitative exploratory research to identify and determine the frequency of specific consequences experienced during simultaneous use and examine the relationship between simultaneous use consequences and particular patterns of use.

Introduction

Alcohol and cannabis are two of the most commonly used substances among young adults in the U.S. (Schulenberg et al., 2019) and heavy use of either substance is associated with significant short and long-term health consequences (Arria et al., 2013; Pearson et al., 2017; Read et al., 2006; Simons et al., 2012; White & Hingson, 2014). Many young adults report using both alcohol and cannabis concurrently (concurrent use; using both substances but not so they overlap) and/or simultaneously (simultaneous use; using both substances in the same occasion so that their effects overlap; Brière et al., 2011; Subbaraman & Kerr, 2015; Terry-McElrath & Patrick, 2018). Based on national survey data with adults age 18 and older, the prevalence of simultaneous use is almost twice that of concurrent use suggesting that when individuals use both alcohol and cannabis they tend to use them so their effects overlap (Subbaraman & Kerr, 2015). Recent studies have found 30% of young adults who drink report past-year simultaneous use (Terry-McElrath et al., 2018) and over half (59%) of college students who drank in the past year reported being “cross-faded” (i.e., feeling the overlapping effects of alcohol and cannabis; Patrick & Lee, 2018). Thus, it is important to examine simultaneous alcohol and cannabis use in order to understand substance use experiences among young adults.

Prior research has found simultaneous use to be greater among those who engage in heavier drinking (Midanik et al., 2007; Terry-McElrath et al., 2013; Terry-McElrath et al., 2019). Young adults who reported past two weeks binge drinking (drinking 4+ drinks for women/5+ drinks for men in a single occasion) at age 18 compared to those who did not were over 5 times more likely to report engaging in simultaneous use at age 19 or 20 (Patrick et al., 2019). Simultaneous use occasions involving heavy drinking are associated with increased negative consequences relative to lighter drinking occasions. (Lee et al., 2020; Mallett et al., 2019). Additionally, individuals who engage in simultaneous use report increased negative consequences compared to those who use alcohol or cannabis alone or engage in only concurrent use (Agosti et al., 2002; Arria et al., 2013; Arterberry et al., 2017; Brière et al., 2011; Earleywine & Newcomb, 1997; Lee et al., 2017; Lipperman-Kreda et al., 2017; Martin et al., 1996; Midanik et al., 2007; Shillington & Clapp, 2001; Subbaraman & Kerr, 2015; Yurasek et al., 2017). Specifically, compared to those who only use alcohol, those who engage in simultaneous use are more likely to report drunk driving, social consequences, and harm to self (Subbaraman & Kerr, 2015). Moreover, compared to those who engage in concurrent use, those who engage in simultaneous use are more likely to report drunk driving (Subbaraman & Kerr, 2015), tickets/warning, and vehicle accidents (Terry-McElrath et al., 2014). Despite the clear public health impact of simultaneous use, the literature on this risky behavior contains several gaps. The goal of this paper was to use qualitative methods to further understand the relationship between simultaneous use and consequences and explore how consequences differ between simultaneous use and single substance use from the perspective of young adults who engage in simultaneous use.

The research that has been conducted on simultaneous use consequences has a number of limitations. First, studies comparing young adults who engage in simultaneous use to young adults who only engage in single substance use (between-person studies) have found those who engage in simultaneous use are more likely to report greater harm to social relationships, employment, academics, and physical health. However, these study designs do not allow us to determine if simultaneous use on any given occasion is the reason that such consequences are being experienced, or whether individuals who engage in simultaneous use are simply riskier individuals who report more negative outcomes (Haas et al., 2015; Jackson et al., 2020; Mallett et al., 2019). Second, while studies comparing simultaneous use events to single substance use events (event-level studies) are better able to identify consequences that are directly related to simultaneous use, these studies have focused on examining total number of consequences. More research is needed to examine which specific consequences are related to simultaneous use compared to single substance use. (Lee et al., 2020; Linden-Carmichael et al., 2020; Mallett et al., 2017; Mallett et al., 2019). Third, the event-level simultaneous use studies that have measured consequences have used items from single substance use (cannabis and/or alcohol) consequence questionnaires, often focusing on alcohol-related consequences (Lee et al., 2017; Linden-Carmichael et al., 2020). Notably, some consequences that occur following simultaneous use may be more unique to alcohol (e.g., blackout; passed out) while others may be more unique to cannabis (e.g., feeling panicked or paranoid). Yet, others may be experienced under the influence of either substance (e.g., dizziness). Whether there are any consequences that are unique to the combination of these two substances is unclear. It may be that prior research is missing important consequence items in current simultaneous use research when relying on consequence measures that have been validated for single substance use (either alcohol or cannabis). Studies comparing the number of negative consequences experienced on single substance use occasions to simultaneous use occasions have reported mixed findings (Lee et al., 2020; Linden-Carmichael et al., 2020; Lipperman-Kreda et al., 2017; Mallett et al., 2019). One possible reason for these discrepant findings may be the different consequences assessed for each study. Identifying the different types of consequences experienced during simultaneous use provides an initial step towards developing a simultaneous use specific consequence assessment that can be used across studies.

In addition to the negative consequences of simultaneous use, positive consequences are also important to consider. From a social learning perspective, bi-directional relationships exist among the individual, environment, and behavior, and direct experience from a behavior and related outcomes may reinforce future behavior (Bandura, 1977). Acute positive consequences experienced during a substance use occasion may be one such reinforcer, helping to explain the maintenance of high-risk substance use behavior, such as simultaneous use. Yet, the majority of simultaneous use research has focused on negative consequences. Only a few studies have examined positive, reinforcing consequences that occur on simultaneous use occasions (Lee et al., 2020; Linden-Carmichael et al., 2020). These studies have found positive consequences (e.g., felt more energetic, felt relaxed, was more social) to be more frequently reported than negative consequences, suggesting positive consequences are an important part of the simultaneous use experience. Similar to negative consequences, examination of positive consequences has been focused on total number of positive consequences, examining consequences in aggregate rather than specific types of consequences of simultaneous use. More research is needed to understand positive and negative consequences associated with simultaneous use events and potential differences in consequences resulting from simultaneous use compared to single substance use events (alcohol-only, cannabis-only).

In addition to (or instead of) certain consequences being unique to simultaneous use (i.e., experienced on simultaneous use occasions, but not experienced during single substance use occasions), some positive and negative consequences experienced may simply be more frequent or more intense during simultaneous use versus single substance use events. However, this is currently unclear. Laboratory-based alcohol and cannabis research suggests that cannabis enhances subjective effects of alcohol intoxication and increases cognitive impairment (Downey et al., 2013; Hartman et al., 2015, 2016; Lukas & Orozco, 2001; Perez-Reyes et al., 1988; Ramaekers et al., 2016). Thus, it may be that consequences experienced are more intense during simultaneous use than single substance use, such as a more severe hangover or an enhanced feeling of relaxation on simultaneous use occasions. To understand differences in experiences of simultaneous use and single substance use consequences it may be important to examine frequency of specific acute consequences and/or examine differences in how people subjectively evaluate the intensity of specific consequences. Exploring how individuals perceive simultaneous use consequences may provide insight into the punishing and/or reinforcing properties of simultaneous use.

Beyond understanding how consequence experiences of simultaneous use differ from those of single substance use, it would be useful to better understand what aspects of the event evoke consequences on one simultaneous use occasion versus another. Two possible predictors include patterns of use (i.e., order of substances, timing of use) and use of harm reduction strategies (i.e., behaviors that reduce negative consequences experienced from substance use such as limiting quantity of substances used). Prior alcohol and cannabis research have shown patterns of use can influence consequences. For example, increased quantity of alcohol and cannabis consumed is associated with more negative consequences; and drinking behaviors such as taking shots, pregaming, and drinking fast are associated with increased consequences (Barnett et al., 2013; Gunn et al., 2020; Hingson & White, 2013; Linden-Carmichael et al., 2018; Merrill, Vermont, et al., 2013; Patrick, 2016). Moreover, our recent qualitative work among heavy drinking college students identified that patterns of simultaneous use were highly variable across individuals. For example, some young adults reported mixing alcohol and cannabis across an event while others reported that they would stop drinking once they started using cannabis on simultaneous use occasions. Also, young adults reported that they used alcohol and cannabis in a particular order, but this order varied among people. Notably, participants endorsed patterns of use they perceived to reduce negative consequences during simultaneous use, suggesting harm reduction strategies are used during simultaneous use occasions (Boyle et al., 2021). Certain strategies related to single substance use patterns have been found to be associated with reductions in negative consequences (Martens et al., 2011; Pearson & Bravo, 2019). Patterns of use when mixing alcohol and cannabis, including those adopted intentionally to reduce harm, may be important predictors of certain types of consequences or more severe negative outcomes.

In sum, to understand simultaneous use experiences it is important to explore for unique consequences and/or patterns of experiences specific to simultaneous use since most of the simultaneous use consequence research has employed single substance use consequence measures. Additionally, understanding what positive and negative consequences are common to simultaneous use and whether the intensity of these consequences differ from single substance use can help us to better characterize simultaneous use outcomes.

Qualitative methods is well suited for such exploratory research as it provides an opportunity to understand individuals’ perceptions about life experiences (Miles & Huberman, 1994; Neale et al., 2005). Such methods are ideal for exploring details about young adults’ substance use and gain insight into the outcomes that result from simultaneous alcohol and cannabis use. Prior published qualitative research examining simultaneous use among adolescents and young adults include one study that examined the contexts of simultaneous use (Price Wolf et al., 2019) and another study that examined motives, patterns, and evaluations of simultaneous use occasions (Boyle et al., 2021). Both of these studies focused on examining predictors of simultaneous use; clearly lacking is qualitative research examining consequences, both positive and negative, of simultaneous use. Qualitative interviews of young adults who engage in simultaneous use allowed for examination of simultaneous use events including detailed accounts of consequences experienced as a result of simultaneous use. Also, qualitative interviews can elicit subjective perceptions from young adults about consequences experienced during simultaneous use events compared to those experienced during single substance use events.

The Present Study

The present study sought to understand consequences experienced during simultaneous use. Understanding types of consequences experienced and factors that influence simultaneous use outcomes may improve quantitative assessment and inform intervention development. A descriptive qualitative study involving interviews with young adults who engage in simultaneous use was conducted to understand perceptions of (1) the positive and negative consequences that result from simultaneous use, (2) how these consequences are similar/different from single substance use, and (3) the factors that influence simultaneous use consequences.

Methods

Participants

Participants (N=36, 23 women, 12 men, 1 trans man) were recruited nationally via social media advertising and locally via university listservs and flyers. Since simultaneous use has been found to be greater among those who drink heavily, we chose to gain insight about simultaneous use experiences from young adults who frequently engage in heavy drinking. Thus, participants were eligible if they were between the ages of 18–25, drank 4+ drinks for women/5+ drinks for men in a single occasion at least twice in the past 30 days, engaged in using alcohol and cannabis so their effects overlapped at least twice in the past 30 days, were living in the U.S., did not report mental health symptoms that were interfering with their everyday functioning, and had not been in treatment for substance use disorder or serious mental illness in the past 6 months. Participants received a $30 Amazon.com gift card for participating.

The mean age of those interviewed was 22 years (SD=1.08). Ethnic and racial representations of the sample were 17% Hispanic/Latino, 11% Asian, 6% Black, 78% White, and 6% other race. The majority (58%) of the sample reported being a current college student; 1 reported being enrolled in a two-year college and 20 reported being enrolled in a four-year college. Most of the young adults (86%) were living in a state where recreational cannabis was illegal at the time of the interviews.

Procedures

All procedures for this study were approved by the Institutional Review Board of Brown University. Flyers posted around the greater Providence, RI area and social media advertisements were used for recruitment. Interested young adults completed a brief online screening survey and those eligible were redirected to provide contact information. These individuals were then contacted to confirm eligibility and schedule an interview session. Interviews were conducted remotely (via Zoom videoconferencing). Young adults consented to the study, completed a brief online survey asking about personal demographics and substance use behavior, and completed a one-on-one interview. Each interview lasted for about 75 minutes following a semi-structured research agenda. Questions most relevant to this study focused on positive and negative consequences of simultaneous use (see Table 1). Interviews were recorded and recordings were transcribed verbatim and de-identified. Data requests for this study can be emailed to the author. This study was not preregistered.

Table 1.

Qualitative Codebook and Interview Questions

Code	Code Definition	Interview Questions
Negative consequences from simultaneous use Negative consequences from simultaneous use differ from single substance use Positive consequences from simultaneous use Positive consequences from simultaneous use differ from single substance use Strategies to avoid negative consequences from simultaneous use Amount of substance use influences consequences of simultaneous use Patterns of substance use influences consequences of simultaneous use	Negative consequences experienced from simultaneous use (e.g., nausea or vomiting) How negative consequences from simultaneous use differ (or don’t differ) from negative consequences experienced during single substance use Positive consequences young adults report experiencing as a result of simultaneous use (e.g., feeling more relaxed; positive sexual experience) How positive consequences from simultaneous use differ (or don’t differ) from positive consequences experienced during single substance use. Strategies used to avoid negative consequences from simultaneous use. How amount of substance use (alcohol quantity and cannabis use) influences simultaneous use consequences and outcomes. How amount of substance use (i.e., order, timing) influences simultaneous use consequences and outcomes.	What kinds of bad or unpleasant things, if any result from mixing alcohol and cannabis? How has this differed from the not so good things you have experienced when only using alcohol? Or only cannabis? What are some good things, if any that resulted from mixing alcohol and cannabis? How has this differed from the good things you have experienced when only using alcohol? Only cannabis? What strategies do you use to avoid negative experiences when mixing alcohol and cannabis? n/a Emergent theme from interviews n/a Emergent theme from interviews

Data was analyzed using the thematic analysis procedures described by Braun and Clarke (2006). Interviews were coded using a codebook that was initially derived from the interview guide, but further refined at the early stages of coding when emergent topics were found to have arisen across interviews. Two researchers coded each transcript independently. Researchers met about each transcript to discuss and resolve any coding discrepancies, bringing all transcripts into 100% agreement. NVivo data analysis software was used for analyses (QSR International, 2021). Codes were collated into potential themes. The themes were revised and reviewed to ensure that they were grounded in the original data and represented the young adults’ narratives. Representative quotes were chosen for each theme and are presented here (see Table 2).

Table 2.

Qualitative Themes about Simultaneous Use Consequences with Representative Quotes

Theme and Representative Quotes	ID (Gender)
Perceived intensity of negative and positive consequences varies across simultaneous use and single substance use occasions (alcohol-only, cannabis-only)
I think a lot of these would be related to just alcohol for me, like blackout memory loss. I guess, yeah, weed probably heightens that because I think I’m pretty prone to that sort of thing and weed definitely affects that.	106 (woman)
I’d say at times the consequences while getting crossed of drinking have been worse than that of drinking itself. I’ve had experiences where I’ve blacked out with both drinking and no cannabis use and drinking with cannabis use but seldom with just cannabis use… I’d say throwing up is worse for getting crossed sometimes than with just drinking alcohol because you get spinny. You start to feel the effects of the weed, and they inversely make you feel more drunk. I think people can’t deal with that.	112 (woman)
Yeah. It’s definitely a little bit different than when I’m just drinking. If I was just using alcohol, there are times where I’ve gotten a little bit sick or nauseous or whatever the case may be, but it definitely intensifies when I’m overlapping the two.	136 (woman)
When it’s mixed, feeling panicked or paranoid is definitely more heightened, I would say absolutely, yeah. I don’t know why, but it just is.	113 (man)
I guess when mixing I’ve been more impulsive—essentially, if I’m just smoking then I’m probably not as impulsive, and I guess where I’ve psyched myself up to—I guess hitting someone up or to meet up with somebody, and so getting crossed definitely gave me I feel like just the extra push with people even more than just drinking. I feel like being crossed gives you that confidence and then if you have a friend hyping you up to do something too, then that is enough. Whereas if you just had the friend and just the smoking, it probably wouldn’t be enough to hype me up to text somebody to hang out that night or something like that.	102 (woman)
Yeah, I think I’m already more social when I drink and in a better mood, but I wouldn’t say it’s necessary that I do both [use alcohol and cannabis] to get that effect, but it definitely maybe enhances that effect.	131 (woman)
I think sleep is pretty similar getting crossed or just using alcohol or weed ‘cause anytime I use a substance, I go to sleep. I sleep pretty well after.	111 (woman)
Engaging in simultaneous use provides unique positive experiences from using both substances that are not able to be experienced by use of one substance alone
I do feel like if I smoke and drink, it’s almost like a nicer feeling than just drinking. When I’m just drinking, it’s like you’re drunk and you’re loud. Then if I smoke and drink, it’s like—I don’t know. It almost feels like you’re able to enjoy the night a little more because you’re more calm, but also still in a high state and feeling drunk.	127 (woman)
I feel like I do get more creative when I smoke, but it’s almost harder to dig through the thoughts. I feel like there are more thoughts, but it’s harder to traverse them. As opposed to when I’m crossed, I feel like the weed causes the thoughts to be there, but then the alcohol causes you to traverse them more easily. As opposed to just drinking. I don’t think I’ve ever had a good idea drinking.	103 (man)
If I just smoke weed, I’m definitely a lot quieter, more like just observing instead of talking, definitely more shy, I’d say. Whereas if I’m just drinking, I’m definitely more outgoing and social. Then if I’m mixing, it’s a unique combination of both.	124 (woman)
I feel like we were more willing to say what was on our minds, and I definitely felt a release of a bit of the stress. I think mixing was a relaxer and also helps me communicate with my friends in a different way… It’s a good way to re-bond with these friends, re-bond and reconnect after not seeing each other as much for a while.	119 (woman)
Definitely felt a sense of comradery with my friends when drinking and smoking. Heightened sense of comradery. I think it probably just made us all feel closer to one another.	110 (man)
Physical consequences from simultaneous use were perceived to result from using too much or in a specific order
Probably the worst I’ve had it was just drinking way too much and smoking too late into the night. Then I get—we call it the spins. It’s just you’re really dizzy. It’s like the whole room is just turning upside down. You can barely walk. You can barely function as it is, barely talk. That’s the worst it can get. I’ve had one time where it got really bad. I thought my heart was gonna stop. If you don’t do it right, it can be a terrible time.	122 (man)
I was definitely borderline blackout, and I don’t remember very much. I can remember feeling extremely nauseous, extremely dizzy, the room was spinning, I had to throw up. That’s definitely the bad part. I find that if I drink eight to ten drinks and then smoke, I’ll get negative effects, whereas if it’s just a drink or two and then smoking, it’s the ideal, I’d say.	124 (woman)
If I smoke first, I usually drink a lot less because I get nauseous more easily. I don’t like vomiting. I don’t think anyone likes vomiting. I usually stop once I start feeling nauseous, which is probably a couple of drinks.	111 (woman)
If you’re drinking too much, then it would probably be a negative experience. If you’re drinking maybe a middle amount or so and then smoke you are probably going to have a negative experience. You feel sloppy with less alcohol when you mix.	128 (woman)
To avoid negative consequences and maximize positive consequences during simultaneous use, young adults strategize around the specific pattern of use
I would say there was one time in particular that I decided to use cannabis after more than four drinks. I was already pretty drunk and then I decided to use cannabis. That was not a pleasant experience. I didn’t feel very good, so yeah. That’s—and then after that, I’ve been even more stricter on myself, like only use cannabis if I’ve had three or four drinks or less because of that night of experience	118 (woman)
Well, I know if I’m planning on going back home after drinking and using cannabis or if I’m planning on going to a friend’s house after drinking and using cannabis, then I’ll try to not drink as much. Or if I know I’m gonna be leaving soon I’ll try and get water and hydrate myself maybe get some food trying to regenerate a little bit. Then I’ll feel more comfortable to go home and go wherever and use it.	123 (man)
Yes, but not by much ‘cause I am pretty good about having a snack and water before I go to bed just ‘cause I learned with time that [laughter] works better, but yeah, no, they’re I’d say consistently every time I mix, I eat something and drink water. Maybe 70 percent of the time, if I’m just drinking, I eat something and drink water… Yeah, but if I mix, it’s a guarantee that I will have something and drink water mostly.	131 (woman)
I feel like I’m trying to make sure everything is the same, so if I’m buzzed off of smoking, and I’m buzzed off of drinking, I wanna be able to get to the point where I’m in the middle where I’m stoned and I’m drunk at the same time. I don’t want it to fluctuate too much, because what’s the point of doing both if you’re not gonna get the result that you want?	113 (man)
I think the main difference for me is that I think I feel like if I have had the right amounts to drink and the right amounts to smoke, I feel like that’s when I’m most comfortable in terms of just being intoxicated overall. I think it puts me in the best mood, again compared to just smoking.	107 (trans man)

Results

A total of 36 individual interviews were completed, at which time saturation was reached for key topics. This sample size exceeds recommendations for qualitative research with homogeneous samples (Boddy, 2016; Dworkin, 2012). At baseline the majority of participants reported drinking (69%, n=25) and using cannabis (81%, n=29) two or more times a week. Thirty-nine percent (n=14) reported engaging in simultaneous use twice a week or more. Fifty percent of young adults reported usually or always using alcohol first during simultaneous use occasions, 14% reported usually or always using cannabis first during simultaneous use occasions, and 36% reported no regular pattern.

Young adults reported a variety of positive and negative consequences resulting from simultaneous use (see Supplemental Materials). The most prevalent negative consequences reported were vomiting (n=23, 64%), nausea (n=16, 44%), spins/dizziness (n=16, 44%), hangovers (n=14, 39%), and blackouts (n=13, 36%). The most prevalent positive consequences reported were feeling relaxed (n=28, 73%), having a fun time (n=23, 64%), feeling social (n=21, 58%), bonding/connecting with others (n=20, 56%), and sleeping better (n=18, 50%). Young adults reported overlap between types of consequences experienced on simultaneous use and single substance use occasions. Participants indicated that certain consequences applied across all types of substance use, while others applied to just simultaneous use and one single substance use but not the other. For example, blackouts, being rude, neglecting school/work, regretted sexual experiences, and feeling outgoing were only discussed as occurring during simultaneous use or alcohol-only occasions, while feeling anxious, and feeling panicked or paranoid were only discussed as occurring on simultaneous use or cannabis-only occasions. No clear theme emerged suggesting that unique negative consequences occur during simultaneous use relative to single-substance use. However, four themes emerged regarding intensity of consequences, unique combinations of positive consequences, and likelihood of negative consequences; these are elaborated upon below.

Perceived intensity of negative and positive consequences varies across simultaneous use and single substance use occasions (alcohol-only, cannabis-only).

The extent to which negative consequences were perceived as more severe and positive consequences were perceived as more enhanced was described to vary both within and across substance use occasions. Young adults reported that sometimes negative consequences were more severe on simultaneous use occasions, while other times consequences were more severe during single substance use occasions. Certain consequences such as vomiting and nausea were typically reported as more severe during simultaneous use. Young adults attributed level of severity to quantity of substances used, the speed of consumption, and spacing of substance use (for simultaneous use). For example, one woman (ID 101) mentioned,

I can get sick on alcohol-only nights, but I think that it’s worse when I smoke, when I mix, when I have too much to drink, and then I try to take more than one hit. I’ll get sick, and yeah, it’s usually worse than when it’s just alcohol.

Young adults reported that positive outcomes on simultaneous use occasions were usually either similar or more enhanced (but not less enhanced) relative to single substance use occasions. For example, one man (ID 103) mentioned that being in a better mood was the same across substance use occasions. He stated:

I was in a better mood [engaging in simultaneous use]. Was I in a better mood as opposed to just using one [substance], though? No. Probably the same.

Often participants reported that positive consequences were more enhanced during simultaneous use compared to single substance use. As stated by one woman (ID 129),

Getting crossed just enhances the effects of both. If I’m only smoking, or if I’m only drinking, the effects are not as strong¹.

Many participants talked about enhancement of specific positive outcomes during simultaneous use. For example, one woman (ID 105) discussed feeling more energetic when engaging in simultaneous alcohol and cannabis use saying:

When I’m crossed, I’m more energetic. Definitely more energetic than if I’m just smoking alone. I feel more energetic, just because I think the intoxication, the intensity of the intoxication is more long-term when getting crossed. I do get energetic when I’m drunk, but it doesn’t last as long unless I keep drinking versus if I’m crossed, and I don’t drink or smoke as much, or at all after becoming crossed. The energy lasts longer overall.

Young adults described the right balance of alcohol and cannabis quantity led to more enhanced positive experiences. For example, one woman (ID 135) stated,

I think just the feeling for me, personally, it’s leveling out the two; whereas, too much weed can make you feel tired and sluggish. Too much booze can make you feel crazy and super hyper. When you have the right level of the two, it’s a really nice feeling.

Engaging in simultaneous use provides unique positive experiences from using both substances that are not able to be experienced by use of one substance alone.

Young adults reported many positive consequences from simultaneous use, particularly positive social consequences. While many of these consequences, such as being more social, more open to meeting people, and laughing with others were reported on both single and simultaneous use occasions, unique bonding experiences were described to occur during simultaneous use. Participants perceived using alcohol and cannabis together resulted in improvement of preexisting relationships (described as bonding or building comradery) by being able to connect with others on a deeper level (i.e., having more meaningful conversations than usual). They reported this deeper level of bonding was much more likely to occur during simultaneous use than single substance use (alcohol-only, cannabis-only). One man (ID 103) said,

Connecting more with the people that you’re smoking with, I think, is a big plus, even more than just being drunk together. Drinking and smoking together is a real bonding thing.

Furthermore, young adults reported that engaging in simultaneous use provides a unique combination of positive experiences from both substances that they would not be able to experience if they used only alcohol or cannabis. Young adults reported the combination of lower inhibition while also feeling more creative was unique to simultaneous use. As stated by one man (ID 113),

I noticed that I get a little more of a body high if I smoke and drink. It’s just you feel more of a heightened sense and feeling less inhibited. I don’t really listen to music too much, but then when I drink and I smoke, I tend to listen to music, so I get all those juices flowing in my brain…it really opens me up to wanna physically bring something into the world with my artwork, more open to the possibility with lower inhibitions.

Other unique combinations of positive experiences included higher energy, but feeling relaxed at the same time, and experiencing both a calm mind and relaxed body from simultaneous use. For example, one man (ID 121) stated,

For alcohol, it makes your body loose. Cannabis makes your mind loose. When you mix them, you loosen out everything. It is its own thing, the best of using both. Your mind is calm and your body is loose.

Young adults emphasized that mixing alcohol and cannabis could result in a combination of the best positive aspects of each substance. They reported experience mixing both substances had led them to find the right quantity of each substance to use to achieve these desirable positive consequences.

Physical consequences from simultaneous use were perceived to result from using too much or in a specific order.

While young adults reported a variety of negative consequences resulting from simultaneous use, they most often described negative consequences that were physical. Though physical consequences were not described as being unique to simultaneous use, some that were reported often during simultaneous use included feeling nauseous, having a headache, “getting the spins”/feeling dizzy, vomiting, blacking out, and having a hangover. For example, one woman (ID 129) stated,

Yeah, so it was pounding. It was dizzy. I don’t even know how I walked out of there. I basically held on to walls. I had a purpose in my head to just go to my car and lay down, and that was all I had to do. This was a bad experience using both.

Young adults perceived that these negative physical consequences often occurred because they used too much alcohol and/or cannabis during these simultaneous use events. However, they also reported that relative to single substance use occasions, on simultaneous use occasions, negative consequences occurred at lower quantities of substance use. For example, one man (ID 134) stated,

Compared to alcohol only…when you mix, it takes a smaller amount of alcohol in order to make you feel like you’re about to throw up, but if it’s only alcohol, then I would say I’d be able to take more alcohol before I felt the need to throw up.

Additionally, many participants reported that using cannabis first and then drinking made them more likely to feel nauseous and sick than using in the opposite order. Participants also reported drinking less when they used cannabis first because this order often led them to feel sick early on during the substance use occasion. One woman (ID 128) stated,

If I smoke first, and then I drink, I normally don’t do that just because I just don’t like the feeling. I think it just makes me feel sick more. If I smoke first and then I drink, I feel like I can’t bring myself to drink more because I feel like I’m going to be sick. Whereas if I drink first and then smoke, I get a little bit more drunk, which is better in the long run.

Exceptions to this pattern of use were evident in the individuals who reported using cannabis throughout the day for recreation and/or medical reasons. These individuals reported almost always being high prior to drinking and that most drinking occasions for them were simultaneous use occasions. These participants did not report negative physical consequences relating to this order of substance use. One such woman (ID 114) said,

Yes. I’m not gonna be drinking alcohol before cannabis ‘cause I don’t enjoy alcohol that much and am always smoking. If I’m gonna drink, I’ll already be smoking.

To avoid negative consequences and maximize positive consequences during simultaneous use, young adults strategize around the specific pattern of use.

Young adults reported avoiding negative consequences and increasing positive consequences by using a number of strategies to limit their alcohol and cannabis use, including monitoring their intake of each substance, setting limits in advance on quantities of substance use, spacing out use of alcohol and cannabis (while effects still overlapped), and alternating substance use with water to stay hydrated. They also reported eating before or during simultaneous use to avoid negative consequences. Participants often described a history of severe negative experiences from simultaneous use that led them to adopt these harm reduction strategies. For example, one man (ID 123) mentioned,

The mistake I made was, I simply drank too much alcohol and didn’t hydrate, and didn’t probably wait enough time to actually sober up from the alcohol. Then I decided to smoke cannabis. Then I ended up throwing up very intensely. I learned my lesson that you have to have moderation, now I use less and always hydrate when mixing.

Prior negative experiences helped young adults realize the ideal patterns of use (e.g., quantities, spacing of substances). They reported a desire to achieve a balance between alcohol and cannabis consumption in order to maximize positive consequences.

Discussion

This is the first qualitative examination of consequences – both positive and negative – of simultaneous use relative to single substance use. Young adults reported a number of different positive and negative consequences experienced during simultaneous use occasions, many of which overlap with consequences experienced during single substance use (alcohol-only, cannabis-only). Yet, they also reported that simultaneous use can result in unique combinations of positive consequences not experienced during single substance use. Findings also revealed use patterns (i.e., quantity, order) that influence simultaneous use consequences and are sometimes approached intentionally.

Young adults mentioned numerous negative and positive consequences they have experienced from simultaneous use, but much of their discussion focused on negative physical and positive social consequences. The negative physical consequences of simultaneous use included consequences that are found on validated single substance use measures (i.e., blackout, vomiting, headaches) including some of the measures which have been used in event-level simultaneous use studies (Lee et al., 2020; Linden-Carmichael et al., 2020). This lack of specificity in types of negative consequences experienced during simultaneous use (compared to single substance use) may help to explain why event-level studies have not consistently shown differences in negative consequences between simultaneous use and single substance use occasions (Lee et al., 2020; Mallett et al., 2019). Positive social consequences of simultaneous use also included some consequences that overlapped across types of substance use (i.e., feeling more social, meeting new friends), but young adults also emphasized bonding or connecting on a deeper level with peers as an important positive consequence, which was rarely connected to single substance use. Notably, the two event-level studies to date that examine positive consequences in aggregate did not include an assessment of such a consequence, with the closest consequence item being “more social” (Lee et al., 2020; Linden-Carmichael et al., 2020).

Additionally, young adults reported positive consequence experiences of simultaneous use as being unique from positive consequence experiences of single substance use. Unique experiences resulted from experiencing a combination of positive experiences they attributed to alcohol alongside positive experiences they attributed to cannabis. Overall, we found that negative consequence experiences do not seem to differ systematically between simultaneous use and single substance use, while positive consequence experiences may. In addition to the unique positive experiences reported during simultaneous use, young adults also reported that positive consequences that were experienced across simultaneous and single substance use were either equally positive or more enhanced during simultaneous use versus single substance use. There was no evidence that the positive effects of single substance use were any less positive when simultaneously using. Thus, it may be that simultaneous use is more reinforcing, while being no more punishing than single substance use. According to behavioral economic theory (MacKillop, 2016), enhanced positive reinforcement from simultaneous use relative to single substance use outcomes or substance free activities could promote maintenance and escalation of subsequent simultaneous use. Thus, one may hypothesize that increased endorsement of unique positive consequence experiences or evaluating positive consequences as more enhanced during simultaneous use may predict future use. It may be that for young adults who engage in heavy drinking, positive consequences outweigh the impact of negative consequences in the overall evaluation of simultaneous use events, which may in turn lead to future use. Positive consequences may reinforce continued engagement in simultaneous use and particular positive consequences may become explicit reasons for engaging in simultaneous use. In light of these findings regarding the reward value of simultaneous use, future work should examine the relationship between positive consequences experienced from simultaneous use and subsequent motives to use both substances so their effects overlap. Existing event-level studies of simultaneous use have examined consequences in aggregate, and thus not been able to capture nuanced differences between simultaneous use and single substance use consequences. Future quantitative research should examine specific consequences and certain combinations of consequences experienced on simultaneous use occasions, identifying which consequences would be important to include in future quantitative assessments. Additionally, for quantitative research examining differences in consequences between simultaneous use and single substance use, researchers may consider measuring severity/enhancement of consequences to ascertain whether simultaneous use is more reinforcing than single substance use. Based on our findings, it may not be the types of consequences, but the perceived intensity of consequences experienced that differentiates simultaneous use from single substance use. Based on previous alcohol research, evaluations of substance use consequences experienced can directly influence evaluation of substance use events and influence future substance use (Barnett et al., 2015; Fairlie et al., 2016; Merrill, Read, et al., 2013). Understanding which positive consequences are most commonly enhanced during simultaneous use may provide insight into what most strongly reinforces future simultaneous use behavior.

Our findings suggest that while young adults perceive simultaneous use results in unique positive consequence experiences, simultaneous use may not necessarily be perceived as riskier (i.e., resulting in more negative consequences) than single substance use. Instead, level of risk for consequences conferred by simultaneous use appears to depend heavily on patterns of use within an event. Young adults reported that heavier quantities of substances used often influenced negative consequences across occasions, but perceived negative consequences during simultaneous use were experienced at lower quantities of substance use compared to single substance use. This aligns with evidence that consuming alcohol while using cannabis increases the concentration of tetrahydrocannabinol (THC) in the blood, which may lead to magnifying the usual effects of cannabis at a particular dose (Hartman et al., 2015; Lukas & Orozco, 2001) and could contribute to increases in negative consequences experienced at lower consumption levels. Young adults also reported that using cannabis prior to alcohol use was more likely to lead to negative consequences than using in the opposite order. It is important to note that these findings show young adults perceive these patterns of use influence simultaneous use outcomes. Quantitative research explicitly testing these patterns of use is needed to determine if such associations between use patterns and consequences occur. Research may reveal the importance of considering both substance use quantity and order when conducting quantitative examinations of simultaneous use. However, as described next, such work is currently limited.

Event-level studies have reported mixed findings as to whether simultaneous use or single substance use (alcohol-only, cannabis-only) events are associated with greater number of negative consequences. Some studies have controlled for alcohol or cannabis use (Lee et al., 2020; Linden-Carmichael et al., 2020), while others have not (Lipperman-Kreda et al., 2017). Two studies examining the relationship between co-use of alcohol and cannabis, alcohol quantity, and negative consequences suggest alcohol quantity may drive the number of consequences experienced on days that both alcohol and cannabis are used (Mallett et al., 2019; Sokolovsky et al., 2020). Yet, more research is needed to examine the relationship between simultaneous use, alcohol quantity, and specific consequences.

When comparing simultaneous use to single substance use, only one substance use quantity can be controlled for or examined (e.g., cannot control for cannabis when comparing simultaneous use to alcohol-only use). While only a handful of studies have compared consequences of simultaneous use events to alcohol-only events (Lee et al., 2020; Mallett et al., 2017) even fewer studies have compared consequences of simultaneous use to cannabis-only events (Linden-Carmichael et al., 2020). Thus, research examining the role that cannabis quantity plays in the relationship between simultaneous use and negative consequences is very limited. That being said, cannabis use in simultaneous use research is often operationalized as any use or frequency of use. Notably, there are no standardized cannabis quantity measures that can be applied across forms of cannabis (e.g., edibles, oil, leaf) that are akin to those used for alcohol quantity (i.e., standard drinks), and individuals may have difficultly estimating quantities of different forms of cannabis used. Nonetheless, frequency measures (e.g., number of cannabis sessions) may not be ideal for understanding how cannabis use quantity influences simultaneous use consequences. While recent work has been conducted to improve self-report assessment of cannabis use quantity across different forms (Cuttler & Spradlin, 2017; Martin-Willett et al., 2020; Prince et al., 2018), such measures have not yet been readily utilized in event-level simultaneous use research. It could also be that the form of cannabis used in addition to the quantity of cannabis used during simultaneous use may influence consequences experienced and thus future quantitative work examining simultaneous use, cannabis quantity and form, and consequences is warranted.

Only one event-level quantitative study to date has examined the relationship between order of substance use and simultaneous use consequences (Gunn et al., 2021). In contrast to participant perceptions noted in the present study, this event-level study found no relationship between substance use ordering and number of negative consequences. The authors of this study acknowledged limitations of their simultaneous use consequence assessment. They only asked about seven individual consequences that were examined in aggregate and the consequences used were derived primarily from subscales of alcohol consequences. With only one event-level quantitative and one qualitative research study exploring the relationship between order of substance use and consequences, we are not yet able to determine with confidence whether and how order of substances may influence simultaneous use outcomes. Yet, our qualitative findings can lead to testable hypotheses for future quantitative studies. For example, based on our qualitative findings if we were to assess order of use, we may hypothesize using cannabis first and then drinking (as opposed to the opposite order) will lead to more negative physical consequences. If future research confirms what we observed here, that using cannabis prior to drinking leads to more risky outcomes, this order could be targeted in harm reduction interventions. For example, a just-in-time intervention could be structured such that if young adults who engage in simultaneous use report cannabis use, they could be sent messaging in real-time reminding them of the greater likelihood of negative consequences if they choose to also drink.

It should also be noted that young adults who identified as engaging in simultaneous use daily, who tended to use throughout the day, stated that they would most often already be high from cannabis prior to drinking. The few individuals that reported this did not discuss negative consequences from this order of use. Such findings suggest it is important to examine both between and within person differences. It may be that people’s use patterns (i.e., frequent daily cannabis use, heavy drinking) and their history of use (i.e., people who have been engaging in simultaneous use for a long time vs. people new to simultaneous use) may influence consequences experienced from simultaneous use. Individuals who frequently use cannabis and have engaged in simultaneous use for many years may (1) have increased tolerance for both substances and (2) utilize more strategies such as spacing out substance use or using less of each substance that may reduce consequences. Future studies might examine simultaneous use events and corresponding consequences for young adult populations who vary in terms of history of use (i.e., those new to engaging in simultaneous use versus those experienced) or vary in terms of their drinking patterns (e.g., moderate drinking [less than 4/5 drinks (women/men) in a single occasion] versus heavy episodic drinking [4+/5+ drinks (women/men) in a single occasion] and cannabis use patterns (e.g., daily use versus infrequent use). Future work could stratify on prior substance use experience when examining simultaneous use and consequences.

Having observed that their patterns of use influenced consequences of simultaneous use, young adults reported altering their use patterns to avoid negative consequences and maximize positive consequences. They mentioned common harm reduction strategies known to be used for single substance use including reducing quantity of use, monitoring use, alternating between drinking water and using substances, and spacing out substance use. Such strategies have been associated with reduction in alcohol and cannabis use and negative consequences in single substance use literature (Bravo et al., 2017; Linden-Carmichael et al., 2018; Pearson, 2013; Pearson & Bravo, 2019). Our previous qualitative study of heavy drinking college students also found young adults engage in particular patterns of use to avoid negative consequences of simultaneous use (Boyle et al., 2021). These students reported 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, spacing out the use of the two substances (yet still reporting using the two substances so effects overlap), often finishing using one type of substance before beginning the second substance, and using less of one or both substances during simultaneous use events. Young adults in the current study discussed that their reasoning to use harm reduction strategies was not solely to avoid negative consequences, also expressing a desire to reach an optimal balance between alcohol and cannabis consumption to achieve the best positive outcomes from simultaneous use.

Further understanding associations between positive and negative consequences and related harm reduction strategies of simultaneous use could inform intervention efforts. Successful alcohol or cannabis interventions often incorporate personalized feedback and employ motivational interviewing techniques to identify relevant reasons for behavior change. The fact that all participants reported both positive and negative consequences for simultaneous use suggest ambivalence toward such polysubstance use and should be utilized during motivational interviewing procedures. For example, knowledge of salient positive and negative consequences of simultaneous use could be useful in conducting decisional balance exercises discussing the pros and cons of simultaneous use. Frequent negative simultaneous use consequences and severity levels could be communicated as part of future intervention work for simultaneous use. Emphasizing negative consequences of simultaneous use and presenting harm reduction strategies could be useful approaches towards helping one reduce their simultaneous use behavior, while acknowledging there are some positive outcomes.

Limitations

Although this study provides a rich, detailed examination of simultaneous use consequences experienced by young adults, this study is not without limitations. Our sample consisted of young adults who were mostly white (78%), female (64%), and currently living in states where recreational cannabis was illegal (86%). The homogenous sample in this study leads to questions as to whether similar or different themes would emerge among more diverse populations. Our sampling strategy did not focus on stratifying by sex, gender, or racial/ethnic identity and thus we were unable to conduct comparisons across these groups. Future studies should aim to recruit larger, more diverse samples to further understand potential group differences in people’s simultaneous use experiences. Additionally, our study resulted in an in-depth examination of simultaneous use among those who report heavy drinking and frequent simultaneous use, thus our findings may not generalize to those who engage in lighter drinking and less frequent simultaneous use. The interviews for this study were conducted between September and November of 2020, a time when many social distancing guidelines were in place for the COVID-19 pandemic. Young adults reported that their substance use differed from that prior to the COVID-19 pandemic and most likely influenced their recent experiences of simultaneous use consequences. Although young adults were probed to discuss both current and pre-pandemic simultaneous use experiences, more current experiences may have been most salient to them during interviews. Since our findings are based on self-report data from individual interviews, social desirability and recall bias should be considered. While this study provides detailed information that allows us to begin to generate research questions about simultaneous use consequences, demonstrating statistical significance of potential associations is not possible with qualitative methods. Likewise, although the frequencies of specific consequences reported in this study may serve as formative work for development of measures of simultaneous use consequences, the quantification of qualitative data should be interpreted with caution. Natural next steps are to conduct quantitative work to better measure frequency of endorsement of specific consequences and to examine associations between patterns of simultaneous use and consequences

Conclusions

Young adults reported many negative and positive consequences of simultaneous use and perceived that patterns of use influence their experience of consequences. These qualitative findings suggest avenues for quantitative assessment and examination of simultaneous use consequences. Future steps could include (1) further identification of specific consequences (positive and negative) to assess or not to assess during simultaneous use occasions with the goal of developing a scale for a self-report consequence measure, (2) understanding the relationship between substance use quantity during simultaneous use events and consequences, (3) examinations of how patterns of use (e.g., order) may influence simultaneous use consequences, and (4) examination of harm reduction strategies used during simultaneous use events. Better quantitative assessment and characterization of simultaneous use consequences may help us to understand the influence of consequences on future risky simultaneous use behavior and inform intervention efforts.

Public Health Significance.

This qualitative study found consequences overlapped between simultaneous alcohol and cannabis use and single substance use occasions, but young adults did discuss unique combinations of positive consequences during simultaneous use. Patterns of use were reported to influence consequences and were sometimes approached intentionally to reduce harms. These findings may inform future quantitative studies such that better quantitative assessment and characterization of simultaneous use consequences may help us to better understand simultaneous use outcomes.