Underage drinking and binge drinking among college students is widespread and known to cause significant harms and hazards for the drinker and those around the drinker [1–3]. Heavy episodic (binge) drinking has been argued to the number one public health hazard and the primary source of preventable morbidity and mortality for the more than six million college students in the United States [4]. Epidemiological evidence has shown that binge drinking is widespread on U.S. college campuses, with almost half of students reporting binge drinking. In addition, binge drinking has been associated with unplanned and unsafe sexual activity, assaults, falls, injuries, criminal violations, and automobile crashes [5–7]. Binge drinkers are 14 times more likely to drive while impaired by alcohol than are nonbinge drinkers [8] and driving while intoxicated is more directly associated with binge drinking than with chronic heavy drinking [9,10]. Approximately half a million college students in U.S. are injured and 1,700 die each year from alcohol-related injuries [11]. Worldwide, 1.8 million deaths annually are the result of injuries cause by hazardous and harmful drinking, accounting for 3.2% of all deaths and 4.0% of disease burden [12].

In the year 2000, the U.S. Surgeon General established a 50% reduction in college binge drinking by the year 2010 as one of its health goals for the United States [13]. Despite various significant efforts to change this health risk behavior, current levels of binge drinking in young people in the U.S. appear to be relatively unchanged from year 2000 levels [14,15]. Thus, the constancy of underage and binge drinking behavior in young people, despite increased attention to the problem, begs the question of what unexamined factors may be contributing to the binge drinking problem. One possible variable that has received extremely little research attention thus far and is the focus of this article is the shift in alcoholic drink preferences in high school and college students in the past decade. Young people have become enamored with the trend of mixing of energy drinks with alcohol (e.g., Red Bull and vodka or other caffeinated cocktails like Jagerbombs, which are a mix of Jagermeister and Red Bull) [16–22]. However, little is known about how commonly these beverages are consumed in the college student population and whether the motivations associated with consumption of these drinks contribute to hazardous drinking.

Energy drinks (e.g., Red Bull, Monster and Rockstar) are beverages marketed with claims of providing users with increased alertness and energy boosts [18]. These beverages contain a variety of compounds including plant-based stimulants (e.g., guarana), simple sugars (e.g., glucose, fructose), amino acids (e.g., taurine) and herbs (e.g., ginseng) [19]. However, most researchers agree that that the extremely high caffeine content (the principal active ingredient) of these beverages drives the stimulant properties that users often report following consumption [21,23]. The U.S. Food and Drug Administration (FDA) does not regulate the caffeine content of energy drinks and the caffeine content of these beverages can contain 150%–300% of the amount of caffeine that the FDA allows for cola beverages [17].

Despite the exponential rise in sales in the U.S. and worldwide energy drink market [24], little research has examined the rates of use and motivations for consumption of energy drinks alone and mixed with alcohol in college students. The limited survey data from college students does reveal that the consumption of energy drinks, alone and in combination with alcohol, seems to be common. Malinauskas and colleagues used a 19 item survey to assess energy drink consumption patterns in 496 college students at a state university in the central Atlantic region of the United States [25]. The authors reported that 51% of participants reported the consumption of at least one energy drink per month. Many of the self-reported energy drinks users consumed three or more energy drinks at a time when combining them with alcohol while partying. Similar findings were reported by O’Brien and colleagues who used a web-based survey to examine consumption patterns in 697 college students [19]. The authors reported that 24% of past 30-day alcohol drinkers reported consuming alcohol mixed with energy drinks (AmED) in the past 30 days. Moreover, students who reported AmED consumption reported significantly higher alcohol-related consequences, such as riding with an intoxicated driver, being physically hurt or injured, and requiring medical treatment, even after adjusting for the amount of alcohol consumed. Similarly, a survey of 602 undergraduate students found that frequency of energy drink consumption was positively associated with a variety of health risk behaviors, such as marijuana use, sexual risk-taking, fighting, and not wearing a seatbelt when riding in a car [18].

Another important limitation to these previous studies is that they did not report typical alcohol consumption patterns for their sample and compare them to national college rates of alcohol use. Typical alcohol use is an important reference point in a survey of AmED use in a college sample since U.S. colleges and universities can differ dramatically in typical alcohol consumption patterns, ranging from almost no students who binge drink to more than 70% of students reporting past 2 week binge drinking [3,26]. Thus, it is unclear from data from previous surveys of AmED use if the participants were typical of the majority of college students in the U.S. in their alcohol consumption patterns. Several national surveys of college students have noted the largely stable pattern of alcohol use on college campuses in the U.S. As one example, the Harvard School of Public Health College Alcohol Surveys have revealed that binge drinking is a widespread problem on college campuses with almost half of the students reporting binge drinking and 1/5 students reporting abstaining from alcohol consumption. However, more moderate to limited alcohol use is observed at religious schools, commuter schools and historically black colleges and universities [3–6].

It is unclear why young drinkers are motivated to consume AmEDs. Preliminary research suggests that motivations important for AmED consumption include to consume the drink while partying and to improve the taste of alcohol [19,25,27,28]. Improved knowledge about motivations for AmED consumption is critical in light of findings from three recent studies that highlight the risks of consuming these drinks. Price and colleagues reported that, relative to alcohol drinking episodes in which energy drinks were not used, participants self-reported drinking significantly more alcohol when using AmEDs [20]. In addition, results from a field study of college student patrons leaving local bars revealed that patrons who had consumed AmEDs were at a 3-fold increased risk of leaving the bar highly intoxicated and a 4-fold increased risk of intending to drive home, compared to other drinking patrons [22]. Finally, results from a recent laboratory study where subjects were blind to beverages that administered revealed that subjects who received an AmED beverage reported feeling more stimulated compared to subjects who received alcohol alone. However, both AmED and alcohol subjects were impaired on an impulse control task, compared to subjects who did not ingest alcohol [17]. Therefore, findings from these three studies are worrisome and indicate that AmEDs may lead to more hazardous drinking.

What is not known is if drinkers of AmEDs are unaware of how the stimulant effects of energy drinks with alcohol reduce sedation associated with drunkenness, or if drinkers are motivated to consume AmEDs because they are aware that the stimulant effects of energy drinks with alcohol can lead to greater drinking and longer drinking episodes. Asking drinkers about their motivations for using AmEDs could help in efforts to disentangle whether the risks that coincide with consuming these drinks are intentional or unintentional. At present, the paucity of knowledge about motivations for using energy drinks with alcohol is problematic for adequately informing the public about the risks of these drinks. Having limited knowledge about the motivations of young people for using these energy drink beverages with alcohol makes it difficult to judge if these beverages are contributing to hazardous binge drinking in young people.

Therefore, the purpose of this study was to collect anonymous survey responses from college students about their alcohol and energy drink consumption habits and their motivations for consuming alcohol mixed with energy drinks. Questions from previously published questionnaires (e.g., the Harvard School of Public Health College Alcohol Survey) were used to survey alcohol use habits. Additional questions were added to further query respondents about typical energy drink usage and the mixing of energy drinks and alcohol. Participants were also asked about a variety of possible motivations for using AmEDs.

The results of this research indicate two major findings. First, the consumption of energy drinks and the consumption of alcohol mixed with energy drinks (AmED) is a relatively common occurrence in college students. The majority of the college students in this sample have tried or are regular consumers of energy drinks (81%). Moreover, 44% of the college students in this sample have tried or are regular consumers of AmEDs. Removing those students who abstain from drinking or who drink alcohol infrequently (44% of the sample), this means that 78% of alcohol users having tried AmEDs or consume them regularly. This finding indicates that AmED consumption has become main stream behavior in college students and is not an isolated phenomenon. Second, the motivations for consuming AmEDs may be leading to more hazardous drinking practices. Motivations for using AmEDs include being able to drink more, to get drunk faster, and to feel less tired while drinking. All participants, regardless of AmED use, reported that they thought that AmEDs are appealing to underage drinkers.

The findings from this study are consistent with previous reports that college students are consuming energy drinks alone and in combination with alcohol, and that this trend is not an isolated development [18,19,25,30]. Previous studies have noted that AmED use, compared to alcohol consumption alone, was associated with greater consumption of quantities alcohol [20] and more deleterious side effects related to drinking, such as being intoxicated, driving after drinking, being injured or requiring medical treatment [19,22]. However, it remained uncertain as to why such outcomes were reported. Recent laboratory evidence suggests that AmEDs lead to enhanced feelings of stimulation while not altering behavioral impairment, compared to alcohol alone [17]. From that lab study, it was plausible to conclude that drinkers might be unaware that AmEDs decrease the sedative properties of alcohol leading the drinker to consume more than intended and resulting in greater risky behavior and more injuries. However, the results of the current study suggest a different interpretation since AmED users state that they are motivated to consume these drinks because they are aware of the sedative-reducing effects of these beverages. They are intentionally choosing them so that they can drink more alcohol than they would be able to otherwise. This suggests that AmEDs may lead to more binge drinking compared to choices of other alcoholic beverages. Moreover, the motives to consume AmEDs are somewhat different than motives to consume energy drinks in isolation. Previous work has established that users of energy drinks are motivated to consume them to increase energy, allay sleepiness, or to boost sports performance [25,27,28]. Prior preliminary research on motivations for consuming AmEDs included wanting to consume the drink while partying and to improve the taste of alcohol [19,25,27,28]. By contrast, our respondents reported being motivated to use AmEDs to alter one’s subjective state when drinking (i.e., feel less tired, get drunk faster). We did not find that our respondents rated improved taste over other forms of alcohol as a major motivation for consuming AmEDs. The role of taste as a motivating factor in the decision to consume AmED beverages warrants further consideration given these different results.

Altering one’s subjective state when drinking may be most problematic on the declining limb of the blood alcohol curve compared to the ascending limb, when the interoceptive cue of sedation is most apparent [31,32]. In the real world when regular alcohol is consumed, it is on the decline of the blood alcohol curve that a drinker feels tired, stops drinking and decides to go home and go to sleep. The AmED user, by contrast, can rely on the stimulant properties of the energy drink to continue drinking more alcohol and for a longer period of time. Disruption of the interoceptive cue of sedation may be a primary reason why AmEDs are riskier than drinking other forms of alcohol [16,17]. For this reason, it may be warranted to consider labeling energy drinks with some form of warning about the risks of combining them with alcohol [21]. In the U.S., such labeling has not occurred.

The present results should be interpreted in light of a few limitations. First, the sample was obtained from one U.S. University, and was a little skewed toward non-Hispanic whites, which limits the generalizability of the results. Although the alcohol consumption patterns reported by the participants were similar to U.S. national norms for college drinking [2–6,14,15], future studies should examine AmED use in college students from a variety of schools, differing in demographic characteristics and from different geographic locations, including outside of the U.S. In addition, market research has revealed that there has been an explosion in the energy drink market over the past decade, with a growth of over 400% from 2003 to 2007. With the worldwide energy drink market estimated at a value of $4.8 billion [24], use rates of energy drinks and AmEDs are probably not stable, but instead likely are increasing. Thus, the current study provides only a snapshot of current consumption rates and future studies should assess use rates of energy drink and AmED use over time to see if AmED use is increasingly in popularity. Finally, the motivations for using these drinks should be replicated and expanded upon, given that the list of possible motivations for AmED use was not exhaustive in this study. Moreover, careful wording of possible motivations is needed to uncover an important distinction between motives for alcohol consumption and AmED consumption. In retrospect, some of our motivations were too general and could have been interpreted by our respondents as answerable in relation to alcohol in general (e.g., the motivation of ‘like the taste’, see Table 4). Given that the motives for alcohol and AmED consumption may differ, carefully worded statements are needed to determine primary motivations for AmED consumption in individuals who consume both types of beverages. In addition, as college students become more familiar with the effects of these beverages, it remains to be seen if they are motivated to use them for the same or different reasons. It is possible that college students may be less motivated to use these drinks over time as they observe more deleterious side effects associated with their use (e.g., seeing peers having accidents or being charged with impaired driving following AmED consumption). Alternatively, the converse could be true as energy drinks gain further popularity and more college students become familiar with the stimulant properties of these beverages and use them as part of their binge drinking activities.

In summary, it appears that alcohol and energy drink co-administration is relatively common among college students and may be contributing to hazardous drinking practices, already a concern with this population that has high rates of binge drinking. The college students who were participants in this study appeared motivated to consume these AmED beverages in a manner consistent with escalating binge drinking (e.g., to suppress sedation, get drunk faster). Moreover, both users and nonusers reported that they thought that AmEDs appeal to underage drinkers. Therefore, it appears that more clinical and research attention should be focused on these alcoholic beverages and how they may be contributing to hazardous drinking practices and future alcohol dependence problems in young people.