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Correlates of use of alcohol mixed with energy drinks among youth across 10 US metropolitan areas
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Correlates of use of alcohol mixed with energy drinks among youth across 10 US metropolitan areas Shivani R. Khan ∗ , Linda B. Cottler, Catherine W. Striley Department of Epidemiology, College of Public Health and Health Professions & College of Medicine, University of Florida, 2004 Mowry Road, Gainesville, FL 32610, United States
a r t i c l e
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Article history: Received 31 August 2015 Received in revised form 18 April 2016 Accepted 25 April 2016 Available online xxx Keywords: Energy drinks Alcohol Adolescents Correlates Youth
a b s t r a c t Background: Predictors of use of alcohol mixed with energy drinks (AmED) among youth have been understudied. The current analyses investigated the prevalence of and correlates for use of AmED among alcohol users from a national study of stimulant use among youth. Methods: The National Monitoring of Adolescent Prescription Stimulants Study (N-MAPSS) assessed behaviors and risk factors for stimulant use from 11,048 youth, 10–18 years of age recruited from entertainment venues across 10 US cities. Of the four cross sections, two had questions on having alcohol mixed with energy drinks (AmED) in the past 30 days along with sociodemographic characteristics, current tobacco and marijuana use and current nonmedical use of prescription opioids, anxiolytics, and stimulants. Only 13 to18 year olds and those who reported alcohol use were included in the analyses. Results: Overall, 28.4% (1392 out of 4905) of the 13 to18 year olds reported past 30-day alcohol use. Among alcohol users, 27% reported having alcohol mixed with energy drinks in the past 30 days. Multivariate logistic regression indicated that use of AmED was significantly associated with tobacco and marijuana use and nonmedical use of prescription stimulants. Conclusions: Underage drinking is common among youth and more than a quarter of these drinkers use AmED. Use of AmED is significantly associated with tobacco and marijuana use and nonmedical use of prescription stimulants. Drug and alcohol intervention programs should educate on the risks of AmED, as the same population is at high-risk for use of AmED and alcohol/drug use. © 2016 Elsevier Ireland Ltd. All rights reserved.
1. Introduction Energy drinks are beverages containing high concentrations of caffeine and other additives such as taurine, carbohydrates, glucuronolactone, 1-carnitine, vitamins, guarana and ginseng (O’Brien et al., 2008; Ishak et al., 2012; Seifert et al., 2011). Energy drinks provide a boost in energy, promote wakefulness and enhance mental alertness and are mostly consumed by adolescents and young adults for these reasons (Seifert et al., 2011; Striley and Khan, 2014). However, due to the high caffeine content in these beverages, teens and young adults who are less tolerant to caffeine may have a greater risk of getting intoxicated (Goldman, 2013). Reports from the Drug Abuse Warning Network (DAWN) showed a two-fold increase in emergency department visits among youth from 2007 to 2011 due to energy drink use (SAMHSA, 2013). Energy drink use
∗ Corresponding author. E-mail address: khanshr1@ufl.edu (S.R. Khan).
has also been linked with heavy alcohol use and illicit drug use among college students (Arria et al., 2010). In recent years, the popularity of consuming alcohol mixed with energy drinks (AmED) has raised concerns among public health officials. Studies have shown that 23% to 56% of college students reported use of AmED in the past 30 days (Malinauskas et al., 2007; O’Brien et al., 2008; Brache and Stockwell, 2011; Miller, 2012; Patrick et al., 2014) with males having higher odds of consuming AmED than females (O’Brien et al., 2008; Miller, 2012). More than half of the college students who used AmED reported it in the context of partying (Malinauskas et al., 2007) and reported increased heavy episodic drinking and weekly drunkenness compared to those using alcohol alone (O’Brien et al., 2008, 2013). Use of AmED is also associated with an increase in alcohol use disorders among users (Reissig et al., 2009). A review of the current literature found consuming alcohol mixed with energy drinks to be more dangerous than consuming alcohol or energy drinks alone (Striley and Khan, 2014). In 2010, the US Food and Drug Administration (FDA) banned the sale of energy drinks premixed with alcohol. However, individuals still
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Please cite this article in press as: Khan, S.R., et al., Correlates of use of alcohol mixed with energy drinks among youth across 10 US metropolitan areas. Drug Alcohol Depend. (2016), http://dx.doi.org/10.1016/j.drugalcdep.2016.04.030
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mix energy drinks with alcohol in venues such as bars, home and other venues (Snipes and Benotsch, 2013). In 2011, the US National Poison Data System reported that of all energy drink-related calls, the rate of adverse events from AmED was higher than energy drinks without alcohol (39.3% versus 15.2% respectively). Among AmED users who called, 68% were under 20 years of age; 77% were subsequently referred to a healthcare facility to seek immediate treatment (Seifert et al., 2013). Moreover, among college students who consumed a similar amount of alcohol, those who mixed it with energy drinks felt less impaired than those who consumed alcohol alone (Marczinski et al., 2013). The use of AmED seems to mask the symptoms of intoxication and to increase alcohol consumption, which may lead to risky sexual activities and risky and illegal driving behavior (O’Brien et al., 2008; Miller, 2012; Eckschmidt et al., 2013; O’Brien et al., 2013). Evidence for the increased risks of mixing alcohol and energy drinks compared to alcohol use alone is clear among college students between the ages of 18 and 24 (O’Brien et al., 2008; Eckschmidt et al., 2013; O’Brien et al., 2013). Few studies have been conducted among younger age groups. In one, a web-based survey among 13–20 year olds, 19.6% endorsed using premixed caffeinated alcoholic beverages or self-mixed alcohol and energy drinks in the past 30 days (Kponee et al., 2014). Those consuming these beverages, compared to those mixing alcohol with coffee, tea or soda, had higher odds of heavy episodic drinking, fighting and experiencing alcohol-related injuries (Kponee et al., 2014). In a study of 15–19 year olds, use of AmED was significantly associated with being male, having a higher number of sex partners, being a current smoker, riding with an intoxicated driver and using marijuana (Flotta et al., 2014). In another study, among 12th graders, Martz et al. (2015) found that 24.8% endorsed use of AmED in the past year and that use was associated with missing classes, evening outings for fun and recreation, binge drinking, marijuana use and illicit drug use. Martz et al. (2015) distinguished between AmED users and nonusers regardless of their alcohol use. While studies have shown a significant association between prescription drug use and energy drink use among college students (Miller, 2008; Arria et al., 2010; Hamilton et al., 2013; Woolsey et al., 2014), such an association has not been studied with use of AmED. Among Canadian high school students, age and sex were not associated with energy drink use in multivariate models, while being employed, having lower educational performance, tobacco, marijuana and prescription drug misuse, as well as binge drinking, high sensation seeking and having been injured were significantly associated (Hamilton et al., 2013; Ilie et al., 2015). Factors associated with energy drink and AmED use thus have been identified for this analysis from the empirical literature. Other factors that may be associated with AmED use are theorized to be factors that are associated with other drug use. Sociodemographic variables such as rurality (Cronk and Sarvela, 1997), and family structure (Barrett and Turner, 2006) have been associated with using other substances. Testing their association with use of AmED may be valuable. AmED use continues to be understudied among US adolescents. The field needs to explicate factors associated with the use of AmED based on prior findings for other drugs, ED alone, and AmED. Factors associated with alcohol use versus AmED use are also needed for increased specificity of association. We had the opportunity to: 1) examine the prevalence of current use of AmED and 2) identify the correlates of AmED among youth 13–18 years of age from 10 US metropolitan areas versus alcohol alone. Identifying the youth at highest risk for use of AmED may help target prevention efforts.
2. Methods 2.1. Sample The National Monitoring of Adolescent Prescription Stimulants Study (N-MAPSS) recruited 11,048 youth 10–18 years of age from the 10 US cities (Boston, MA; New York, NY; Philadelphia, PA; Tampa, FL; Cincinnati, OH; Houston, Texas; St. Louis; MI; Denver, CO; Los Angeles, CA; and Seattle, WA) to investigate the prevalence of prescription stimulant use and misuse and associated risk behaviors. N-MAPSS used an entertainment-intercept venue method, recruiting from movie theatres, shopping malls, libraries, parks, sports and recreational centers, arcades and skate parks in prespecified zip codes in urban, suburban and rural areas. The sample in N-MAPSS was highly representative of 2010 US census when age, sex, race and rurality for each of the cities were compared. Surveys were completed by trained, certified interviewers in four cross sections: Fall, 2008, Spring, 2009, Fall, 2010 and Spring, 2011. The reliability of the assessment was found to be high (kappas = 0.6–1.0) in a test-retest study design (Cottler et al., 2013). The Washington University in St. Louis Institutional Review Board approved the study protocol and waived written informed consent. Further details on the study methodology have been published (Cottler et al., 2013). For this analysis, data was taken from the last two cross sections (n = 5569), which included a question on mixing alcohol and energy drinks (described below). Youth who reported no alcohol use in the past 30 days were excluded. Only 17 youth aged 10–12 years of age reported alcohol use in the past 30 days; hence, 10–12 year olds were excluded from analyses. The total number of 13–18 year olds in the sample was 4905. Data for these analyses were limited to the 13–18 year olds who reported alcohol use in the past 30 days from the last two cross sections (n = 1392). 2.2. Measures All data came from the self-reported booklet assessment used in N-MAPSS. 2.2.1. Alcohol use. To assess alcohol use, youth were asked, “In the last 30 days, on how many days did you drink alcohol?” Those who reported consuming alcohol on 1 or more days in the past 30 days were categorized as alcohol users and were included in the analyses. 2.2.2. AmED use. Youth who reported alcohol use in the past 30 days were asked, “Have you mixed alcohol and energy drinks together in the past 30 days?” Youth who responded “yes” were categorized as AmED users. Those who responded “no” were categorized as alcohol only users. 2.2.1. Sociodemographic characteristics. Sociodemographic variables included self-reported age, gender, race, area of residence, perceived average grades and living arrangement. Age was categorized into 13–14 year olds, 15–16 year olds, and 17–18 year olds. Race was divided into Caucasian, African American, Hispanic, Asian, and others (Alaskan Native, Asian American, Middle Eastern, Pacific Islander, Multiracial). Area of residence was categorized into urban, suburban, and rural by city limits, proximity to city limits and population density, using US census criteria. Self-reported average grades in school were dichotomized into As or Bs and Cs or lower. Living arrangement was categorized into three groups: living with both parents, living with either mom or dad, or living with foster parents, relatives or others.
Please cite this article in press as: Khan, S.R., et al., Correlates of use of alcohol mixed with energy drinks among youth across 10 US metropolitan areas. Drug Alcohol Depend. (2016), http://dx.doi.org/10.1016/j.drugalcdep.2016.04.030
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2.2.2. Current tobacco use. First, youth were asked, “Have you ever smoked a cigarette?” Youth who gave a positive response to this question were further asked “Do you still smoke cigarettes every day or some days. Possible responses were ‘No’, “Yes, I currently smoke cigarettes everyday”, and “Yes, I currently smoke cigarettes some days”. Youth who reported smoking every day or some days were categorized as current tobacco users and those who responded “no” to the question were categorized as not current tobacco users. 2.2.3. Current marijuana use. To determine current marijuana use, youth were asked, “In the last 30 days, on how many days did you use marijuana?” Youth who reported marijuana use on 1 or more days in the last 30 days were categorized as current marijuana users and those who reported use on 0 days in the last 30 days were categorized as not current marijuana users (they may have used, but were not currently using). 2.2.4. Current nonmedical use of prescription opioids, prescription anxiolytics and prescription stimulants. To measure prescription opioid use, youth were asked if they had taken Vicodin® (hydrocodone) or OxyContin® (oxycodone) in the past 30 days. Pictures of the medications were shown. Youth who reported using Vicodin® or OxyContin® in the past 30 days were asked about all the ways they had used the drug, if they had a prescription or refill, or if they had used medication that belonged to someone else in the past 30 days. Those who reported use of Vicodin® or OxyContin® by routes other than by mouth (snorted or sniffed, smoked, other), use without a prescription for use or refill, or use of medications that belonged to someone else in the past 30 days were coded as current nonmedical prescription opioid users; those who did not report any of these were coded as not current nonmedical prescription opioid users. Similar questions were asked to capture current nonmedical use of prescription anxiolytics (Xanax® or Valium® ) and current nonmedical use of prescription stimulants (Adderall® , Ritalin® , Daytrana® , Concerta® and Vyvanse® ). 2.3. Statistical analyses Pearson’s chi-squared tests were used to analyze the descriptive statistics by users of AmED and alcohol only users. Multivariate logistic regression was used to compare the relative strength of associations between use of AmED and the stated factors. SAS 9.4 was used for all analyses. 3. Results Out of 4905 13–18 year olds, 1392 (28.4%) reported consuming alcohol on one or more days in the past 30 days. Among them, 27% (n = 376) reported mixing alcohol and energy drinks in the past 30 days; the remaining youth reported alcohol only use. Among the sample, 25% reported current tobacco use and 47.1% reported current marijuana use. Similarly, 7.5%, 2.2%, and 8.8% reported current nonmedical use of prescription opioids, anxiolytics, and stimulants, respectively. Table 1 shows the sociodemographic characteristics and correlates (current tobacco use, current marijuana use, current nonmedical use of prescription opioids, anxiolytics and stimulants) by use of AmED versus alcohol only use. Univariate analysis indicated no difference by age (p = 0.59), sex (p = 0.11), area of residence (p = 0.19) or living arrangements (p = 0.13). Significant differences between users of AmED and alcohol only were found by selfreported race (p = 0.03) and average grades (p < 0.001). Specifically, Caucasians, African Americans, and Asians reported higher use of alcohol only than AmED. In contrast, Hispanics and “other” races
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reported higher use of AmED than alcohol only. Additionally, more users of AmED reported lower grades than alcohol only users. Users of AmED versus alcohol only users were significantly more likely to report current tobacco use (37.2% versus 20.5%), current marijuana use (63.8% versus 40.9%) and nonmedical use of prescription opioids (12.5% versus 5.7%), anxiolytics (4.8% versus 1.3%), and stimulants (15.7 versus 6.2%). Multivariate logistic regression predicting use of AmED indicated that sociodemographic variables were not significant predictors of such use. The odds of mixing alcohol and energy drinks (use of AmED) compared to alcohol only continued to be higher among current than non-smokers (OR: 1.63; 95% CI: 1.22, 2.17), and were twice that for current marijuana users compared to those who did not endorse current marijuana use (OR: 1.99; 95% CI: 1.52, 2.59). Moreover, the odds of mixing alcohol and energy drinks versus alcohol only were more than twice as high among those who reported current nonmedical use of used prescription stimulants (OR: 2.13; 95% CI: 1.41, 3.23) compared to those who did not report such use. Nonmedical use of prescription opioids and anxiolytics was not associated with use of AmED Table 2.
4. Discussion As far as we know, this is the first study to report the correlates of use of AmED among youth between 13–18 years of age across the US. In this study, 27% of youth used alcohol mixed with energy drinks in the past 30 days. Our findings in this younger age group were similar to the findings of studies among college students (23–56%) (Malinauskas et al., 2007; O’Brien et al., 2008; Brache and Stockwell, 2011; Miller, 2012; Patrick et al., 2014) but were higher than those among 13–20 year olds surveyed using the web (Kponee et al., 2014). We thus add to the scant literature on this use among US adolescents. Unlike the results of the study conducted among 15–19 year olds (Flotta et al., 2014) and those of college students (O’Brien et al., 2008; Miller, 2012) that found an increased risk of AmED use among males, our analyses found no difference between use of AmED and alcohol only use by sex. Just as the proportion of youth drinking alcohol has recently shifted from more male to a more genderneutral pattern (White and Huselid, 1997; Wallace et al., 2003), so has the proportion of AmED users shifted. We may have captured such a shift due to the large size of our sample and the diversity of participants. The break down by race showed slightly different choice for alcohol only versus use of AmED, but in the multivariate model, race did not predict the use of AmED. Other factors found in prior studies of energy drink and substance use were not significantly associated with use of AmED, including rurality (Cronk and Sarvela, 1997), family composition (Barrett and Turner, 2006) and school performance (Hamilton et al., 2013; Ilie et al., 2015). Behavioral factors for use of AmED were consistent with studies of older youth. For instance, current tobacco users and marijuana users were almost twice as likely to be users of AmED, consistent with other studies (Flotta et al., 2014; Hamilton et al., 2013 and Ilie et al., 2015). Martz and colleagues had also shown an association between use of AmED and marijuana use and illicit drug use (Martz et al., 2015). Two studies among college students showed an association between energy drink use and nonmedical use of prescription stimulants (Arria et al., 2010; Woolsey et al., 2014). Moreover, a study among Canadian adolescents found an association between energy drink use and nonmedical use of prescription drugs (Hamilton et al., 2013). We also found an association between use of AmED and nonmedical use of prescription stimulants among our younger national sample. The increased nonmedical use of prescription stimulants in users of AmED may be explained by two factors. First, adolescents may use energy drinks to overcome the
Please cite this article in press as: Khan, S.R., et al., Correlates of use of alcohol mixed with energy drinks among youth across 10 US metropolitan areas. Drug Alcohol Depend. (2016), http://dx.doi.org/10.1016/j.drugalcdep.2016.04.030
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Table 1 Sociodemographic and behavioral characteristics by use of AmED among 13–18 years old alcohol users (n = 1392). Characteristic
Sociodemographic Age 13–14 15–16 17–18 Sex Male Race Caucasian African American Hispanic Asian Other Area of Residence Urban Suburban Rural Average Grades As or Bs Cs or lower Living arrangement Both Mom and dad Either mom/dad Foster parents/relatives/others Behavioral Current tobacco use Current marijuana use Current nonmedical prescription opioid use Current nonmedical prescription anxiolytic use Current nonmedical prescription stimulant use * ** ***
Overall(n = 1392)
Use of AmED(n = 376, 27%)
Alcohol only use(n = 1016, 73%)
N (%)
N (%)
N (%)
p value
165 (11.8) 531 (38.2) 696 (50.0)
41 (10.9) 139 (37.0) 196 (52.1)
124 (12.2) 392 (38.6) 500 (49.2)
0.593
628 (45.1)
183 (48.7)
445 (43.8)
0.105
711 (51.2) 183 (13.2) 271 (19.5) 68(4.9) 157 (11.3)
187 (49.7) 41 (10.9) 83 (22.1) 12 (3.2) 53 (14.1)
524 (51.7) 142 (14.0) 188 (18.5) 56 (5.5) 104 (10.3)
0.0316*
605 (43.5) 567 (40.7) 220 (15.8)
161 (42.8) 165 (43.9) 50 (13.3)
444 (43.7) 402 (39.6) 170 (16.7)
0.187
984 (70.7) 408 (29.3)
238 (63.3) 138 (36.7)
746 (73.4) 270 (26.6)
0.0002**
707 (50.8) 513 (36.9) 172 (12.4)
180 (47.9) 139 (37.0) 57 (15.2)
527 (51.9) 374 (36.8) 115 (11.3)
0.126
348 (25.0) 656 (47.1) 105 (7.5) 31 (2.2) 122 (8.8)
140 (37.2) 240 (63.8) 47 (12.5) 18 (4.8) 59 (15.7)
208 (20.5) 416 (40.9) 58 (5.7) 13 (1.3) 63 (6.2)
<0.0001*** <0.0001*** <0.0001*** <0.0001*** <0.0001***
p < 0.05. p < 0.001. p < 0.0001.
Table 2 Adjusted odds ratios for the association between AmED use and sociodemographic and behavioral characteristics among 13–18 years old alcohol users (n = 1392). Characteristic Sociodemographic Age 15–16 vs. 13–14 17–18 vs. 13–14 Sex (Male vs. female) Race Caucasian vs. other African American vs. other Hispanic vs. other Asian vs. other Area of Residence Urban vs. rural Suburban vs. rural Average Grades (Cs or lower vs. As or Bs) Living arrangement Either mom/dad vs. both Mom and dad Foster parents/relatives/others vs. both Mom and dad Behavioral Current tobacco use (Yes vs. no) Current marijuana use (Yes vs. no) Current nonmedical prescription opioid use (Yes vs. no) Current nonmedical prescription anxiolytic use (Yes vs. no) Current nonmedical prescription stimulant use (Yes vs. no)
Alcohol only use
Use of AmEDAOR (95% CI)
ref ref ref
0.98 (0.64, 1.50) 1.03 (0.68, 1.57) 1.05 (0.81, 1.35)
ref ref ref ref
0.80 (0.54, 1.18) 0.62 (0.38, 1.04) 1.07 (0.68, 1.66) 0.50 (0.24, 1.05)
ref ref ref
1.18 (0.79, 1.74) 1.39 (0.94, 2.04) 1.21 (0.91, 1.59)
ref ref
0.91 (0.69, 1.20) 1.09 (0.74, 1.61)
ref ref ref ref ref
1.63 (1.22, 2.17)** 1.99 (1.52, 2.59)*** 1.27 (0.80, 2.02) 1.79 (0.80, 4.01) 2.13 (1.41, 3.23)**
ref = reference. * p < 0.05. ** p < 0.001. *** p < 0.0001.
sedating effect of alcohol; when this is not enough, they may turn to more powerful prescription stimulants. Second, adolescents may try to maximize their activation of the pleasure-reward circuit. Energy drinks, similar to prescription stimulants, have ingredients (taurine, caffeine, glucose, guarana, ginseng, etc.) that increase the
release of pleasure-reward neurotransmitters in the brain. Regular energy drink users may use both energy drinks and prescription stimulants for this purpose (Woolsey et al., 2014). Future research should test hypotheses from both of these proposed mechanisms.
Please cite this article in press as: Khan, S.R., et al., Correlates of use of alcohol mixed with energy drinks among youth across 10 US metropolitan areas. Drug Alcohol Depend. (2016), http://dx.doi.org/10.1016/j.drugalcdep.2016.04.030
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The findings reported herein are subject to several limitations. Data were cross-sectional; therefore, causal inferences cannot be drawn. Self-reported data may have been biased by social desirability or recall. However, data were collected anonymously and the time periods assessed would be easily remembered (energy drink use in the past seven days and alcohol use and mixing energy drink and alcohol questions in the past 30 days). Because we only asked if participants had used energy drinks (without regard to whether or not they mixed them) in the past 7 days, and we asked about mixing them with alcohol in the past 30 days, we had to assume that the youth who endorsed mixing were also endorsing use of energy drinks. Restricting the sample to those who had used in the past 7 days would have biased our results to those who used during both time periods. The way the question on mixing was asked might have underestimated true users if the youth misunderstood the question to only include those who mixed the drinks for themselves and did not think that premixed or drinks made by others should be included. Findings are only generalizable to alcohol users only since only alcohol users can use AmED. Moreover, important indicators of use of AmED such as personality variables, drinking motives and levels of previous substance use experience were not measured in this study and these factors might have been important. The study also has strengths. The sample size of this study was large and was highly representative of the youth in these areas according to the results of the 2010 US census (Cottler et al., 2013). We uniquely captured data among out-of-school youth through an entertainment-intercept venue method and had ethnic diversity. Social desirability bias was less likely when compared to household or school based studies since we did not require parental approval for the NMAPSS study. Youth who had been expelled or were home schooled were included while they are missing from school-based studies. Knowing the increased risks for adverse events and outcomes associated with mixing alcohol and energy drinks, we set out to identify characteristics of youth engaging in such mixing. Based on our findings, about 28% of the 13–18 years olds exhibit underage drinking and the use of AmED is common among these alcohol users, with more than a quarter reporting consumption of AmED in the past 30 days. Tobacco and marijuana use and nonmedical use of prescription stimulants are significantly associated with such use. To help prevent youth from mixing alcohol and energy drinks, prevention efforts should target youth who engage in alcohol and drug use. Drug and alcohol intervention programs should incorporate education on the risks of combining alcohol and energy drinks, as the same population is at high risk for use of AmED and alcohol/drug use. The findings herein add to the literature suggesting an association between use of AmED and the nonmedical use of prescription stimulants. Conflict of interest There are no conflicts of interest. Role of funding source N-MAPSS was conducted under contract with Pinney Associates, Inc., with funding provided by Shire Development LLC and Noven Therapeutics (PI: LB Cottler). Contributors Ms. Khan helped develop the aims, conducted statistical analyses, prepared the tables and tables and wrote the initial draft of the manuscript. Dr. Cottler was the PI of the N-MAPSS study. She had oversight over the data collection and participated in some data
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collection herself. She managed the overall study and edited each draft of this manuscript. Dr. Striley collected data and supervised the staff as well as the preparation of this manuscript including shaping the aims and methods. She was a co-investigator on the N-MAPSS study. Acknowledgement We would like to thank all the participants of this study without whose support this study would not have been possible. References Arria, A.M., Caldeira, K.M., Kasperki, S.J., O’Grady, K.E., Vincent, K.B., Griffiths, R.R., Wish, E.D., 2010. Increased alcohol consumption, nonmedical prescription drug use, and illicit drug use are associated with energy drink consumption among college students. J. Addict. Med. 4, 74–80, http://dx.doi.org/10.1097/ ADM.0b013e3181aa8dd4. Barrett, A.E., Turner, R.J., 2006. Family structure and substance use problems in adolescence and early adulthood: examining explanations for the relationship. 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Contents lists available at ScienceDirect
Drug and Alcohol Dependence journal homepage: www.elsevier.com/locate/drugalcdep
Full length article
Correlates of use of alcohol mixed with energy drinks among youth across 10 US metropolitan areas Shivani R. Khan ∗ , Linda B. Cottler, Catherine W. Striley Department of Epidemiology, College of Public Health and Health Professions & College of Medicine, University of Florida, 2004 Mowry Road, Gainesville, FL 32610, United States
a r t i c l e
i n f o
Article history: Received 31 August 2015 Received in revised form 18 April 2016 Accepted 25 April 2016 Available online xxx Keywords: Energy drinks Alcohol Adolescents Correlates Youth
a b s t r a c t Background: Predictors of use of alcohol mixed with energy drinks (AmED) among youth have been understudied. The current analyses investigated the prevalence of and correlates for use of AmED among alcohol users from a national study of stimulant use among youth. Methods: The National Monitoring of Adolescent Prescription Stimulants Study (N-MAPSS) assessed behaviors and risk factors for stimulant use from 11,048 youth, 10–18 years of age recruited from entertainment venues across 10 US cities. Of the four cross sections, two had questions on having alcohol mixed with energy drinks (AmED) in the past 30 days along with sociodemographic characteristics, current tobacco and marijuana use and current nonmedical use of prescription opioids, anxiolytics, and stimulants. Only 13 to18 year olds and those who reported alcohol use were included in the analyses. Results: Overall, 28.4% (1392 out of 4905) of the 13 to18 year olds reported past 30-day alcohol use. Among alcohol users, 27% reported having alcohol mixed with energy drinks in the past 30 days. Multivariate logistic regression indicated that use of AmED was significantly associated with tobacco and marijuana use and nonmedical use of prescription stimulants. Conclusions: Underage drinking is common among youth and more than a quarter of these drinkers use AmED. Use of AmED is significantly associated with tobacco and marijuana use and nonmedical use of prescription stimulants. Drug and alcohol intervention programs should educate on the risks of AmED, as the same population is at high-risk for use of AmED and alcohol/drug use. © 2016 Elsevier Ireland Ltd. All rights reserved.
1. Introduction Energy drinks are beverages containing high concentrations of caffeine and other additives such as taurine, carbohydrates, glucuronolactone, 1-carnitine, vitamins, guarana and ginseng (O’Brien et al., 2008; Ishak et al., 2012; Seifert et al., 2011). Energy drinks provide a boost in energy, promote wakefulness and enhance mental alertness and are mostly consumed by adolescents and young adults for these reasons (Seifert et al., 2011; Striley and Khan, 2014). However, due to the high caffeine content in these beverages, teens and young adults who are less tolerant to caffeine may have a greater risk of getting intoxicated (Goldman, 2013). Reports from the Drug Abuse Warning Network (DAWN) showed a two-fold increase in emergency department visits among youth from 2007 to 2011 due to energy drink use (SAMHSA, 2013). Energy drink use
∗ Corresponding author. E-mail address: khanshr1@ufl.edu (S.R. Khan).
has also been linked with heavy alcohol use and illicit drug use among college students (Arria et al., 2010). In recent years, the popularity of consuming alcohol mixed with energy drinks (AmED) has raised concerns among public health officials. Studies have shown that 23% to 56% of college students reported use of AmED in the past 30 days (Malinauskas et al., 2007; O’Brien et al., 2008; Brache and Stockwell, 2011; Miller, 2012; Patrick et al., 2014) with males having higher odds of consuming AmED than females (O’Brien et al., 2008; Miller, 2012). More than half of the college students who used AmED reported it in the context of partying (Malinauskas et al., 2007) and reported increased heavy episodic drinking and weekly drunkenness compared to those using alcohol alone (O’Brien et al., 2008, 2013). Use of AmED is also associated with an increase in alcohol use disorders among users (Reissig et al., 2009). A review of the current literature found consuming alcohol mixed with energy drinks to be more dangerous than consuming alcohol or energy drinks alone (Striley and Khan, 2014). In 2010, the US Food and Drug Administration (FDA) banned the sale of energy drinks premixed with alcohol. However, individuals still
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mix energy drinks with alcohol in venues such as bars, home and other venues (Snipes and Benotsch, 2013). In 2011, the US National Poison Data System reported that of all energy drink-related calls, the rate of adverse events from AmED was higher than energy drinks without alcohol (39.3% versus 15.2% respectively). Among AmED users who called, 68% were under 20 years of age; 77% were subsequently referred to a healthcare facility to seek immediate treatment (Seifert et al., 2013). Moreover, among college students who consumed a similar amount of alcohol, those who mixed it with energy drinks felt less impaired than those who consumed alcohol alone (Marczinski et al., 2013). The use of AmED seems to mask the symptoms of intoxication and to increase alcohol consumption, which may lead to risky sexual activities and risky and illegal driving behavior (O’Brien et al., 2008; Miller, 2012; Eckschmidt et al., 2013; O’Brien et al., 2013). Evidence for the increased risks of mixing alcohol and energy drinks compared to alcohol use alone is clear among college students between the ages of 18 and 24 (O’Brien et al., 2008; Eckschmidt et al., 2013; O’Brien et al., 2013). Few studies have been conducted among younger age groups. In one, a web-based survey among 13–20 year olds, 19.6% endorsed using premixed caffeinated alcoholic beverages or self-mixed alcohol and energy drinks in the past 30 days (Kponee et al., 2014). Those consuming these beverages, compared to those mixing alcohol with coffee, tea or soda, had higher odds of heavy episodic drinking, fighting and experiencing alcohol-related injuries (Kponee et al., 2014). In a study of 15–19 year olds, use of AmED was significantly associated with being male, having a higher number of sex partners, being a current smoker, riding with an intoxicated driver and using marijuana (Flotta et al., 2014). In another study, among 12th graders, Martz et al. (2015) found that 24.8% endorsed use of AmED in the past year and that use was associated with missing classes, evening outings for fun and recreation, binge drinking, marijuana use and illicit drug use. Martz et al. (2015) distinguished between AmED users and nonusers regardless of their alcohol use. While studies have shown a significant association between prescription drug use and energy drink use among college students (Miller, 2008; Arria et al., 2010; Hamilton et al., 2013; Woolsey et al., 2014), such an association has not been studied with use of AmED. Among Canadian high school students, age and sex were not associated with energy drink use in multivariate models, while being employed, having lower educational performance, tobacco, marijuana and prescription drug misuse, as well as binge drinking, high sensation seeking and having been injured were significantly associated (Hamilton et al., 2013; Ilie et al., 2015). Factors associated with energy drink and AmED use thus have been identified for this analysis from the empirical literature. Other factors that may be associated with AmED use are theorized to be factors that are associated with other drug use. Sociodemographic variables such as rurality (Cronk and Sarvela, 1997), and family structure (Barrett and Turner, 2006) have been associated with using other substances. Testing their association with use of AmED may be valuable. AmED use continues to be understudied among US adolescents. The field needs to explicate factors associated with the use of AmED based on prior findings for other drugs, ED alone, and AmED. Factors associated with alcohol use versus AmED use are also needed for increased specificity of association. We had the opportunity to: 1) examine the prevalence of current use of AmED and 2) identify the correlates of AmED among youth 13–18 years of age from 10 US metropolitan areas versus alcohol alone. Identifying the youth at highest risk for use of AmED may help target prevention efforts.
2. Methods 2.1. Sample The National Monitoring of Adolescent Prescription Stimulants Study (N-MAPSS) recruited 11,048 youth 10–18 years of age from the 10 US cities (Boston, MA; New York, NY; Philadelphia, PA; Tampa, FL; Cincinnati, OH; Houston, Texas; St. Louis; MI; Denver, CO; Los Angeles, CA; and Seattle, WA) to investigate the prevalence of prescription stimulant use and misuse and associated risk behaviors. N-MAPSS used an entertainment-intercept venue method, recruiting from movie theatres, shopping malls, libraries, parks, sports and recreational centers, arcades and skate parks in prespecified zip codes in urban, suburban and rural areas. The sample in N-MAPSS was highly representative of 2010 US census when age, sex, race and rurality for each of the cities were compared. Surveys were completed by trained, certified interviewers in four cross sections: Fall, 2008, Spring, 2009, Fall, 2010 and Spring, 2011. The reliability of the assessment was found to be high (kappas = 0.6–1.0) in a test-retest study design (Cottler et al., 2013). The Washington University in St. Louis Institutional Review Board approved the study protocol and waived written informed consent. Further details on the study methodology have been published (Cottler et al., 2013). For this analysis, data was taken from the last two cross sections (n = 5569), which included a question on mixing alcohol and energy drinks (described below). Youth who reported no alcohol use in the past 30 days were excluded. Only 17 youth aged 10–12 years of age reported alcohol use in the past 30 days; hence, 10–12 year olds were excluded from analyses. The total number of 13–18 year olds in the sample was 4905. Data for these analyses were limited to the 13–18 year olds who reported alcohol use in the past 30 days from the last two cross sections (n = 1392). 2.2. Measures All data came from the self-reported booklet assessment used in N-MAPSS. 2.2.1. Alcohol use. To assess alcohol use, youth were asked, “In the last 30 days, on how many days did you drink alcohol?” Those who reported consuming alcohol on 1 or more days in the past 30 days were categorized as alcohol users and were included in the analyses. 2.2.2. AmED use. Youth who reported alcohol use in the past 30 days were asked, “Have you mixed alcohol and energy drinks together in the past 30 days?” Youth who responded “yes” were categorized as AmED users. Those who responded “no” were categorized as alcohol only users. 2.2.1. Sociodemographic characteristics. Sociodemographic variables included self-reported age, gender, race, area of residence, perceived average grades and living arrangement. Age was categorized into 13–14 year olds, 15–16 year olds, and 17–18 year olds. Race was divided into Caucasian, African American, Hispanic, Asian, and others (Alaskan Native, Asian American, Middle Eastern, Pacific Islander, Multiracial). Area of residence was categorized into urban, suburban, and rural by city limits, proximity to city limits and population density, using US census criteria. Self-reported average grades in school were dichotomized into As or Bs and Cs or lower. Living arrangement was categorized into three groups: living with both parents, living with either mom or dad, or living with foster parents, relatives or others.
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2.2.2. Current tobacco use. First, youth were asked, “Have you ever smoked a cigarette?” Youth who gave a positive response to this question were further asked “Do you still smoke cigarettes every day or some days. Possible responses were ‘No’, “Yes, I currently smoke cigarettes everyday”, and “Yes, I currently smoke cigarettes some days”. Youth who reported smoking every day or some days were categorized as current tobacco users and those who responded “no” to the question were categorized as not current tobacco users. 2.2.3. Current marijuana use. To determine current marijuana use, youth were asked, “In the last 30 days, on how many days did you use marijuana?” Youth who reported marijuana use on 1 or more days in the last 30 days were categorized as current marijuana users and those who reported use on 0 days in the last 30 days were categorized as not current marijuana users (they may have used, but were not currently using). 2.2.4. Current nonmedical use of prescription opioids, prescription anxiolytics and prescription stimulants. To measure prescription opioid use, youth were asked if they had taken Vicodin® (hydrocodone) or OxyContin® (oxycodone) in the past 30 days. Pictures of the medications were shown. Youth who reported using Vicodin® or OxyContin® in the past 30 days were asked about all the ways they had used the drug, if they had a prescription or refill, or if they had used medication that belonged to someone else in the past 30 days. Those who reported use of Vicodin® or OxyContin® by routes other than by mouth (snorted or sniffed, smoked, other), use without a prescription for use or refill, or use of medications that belonged to someone else in the past 30 days were coded as current nonmedical prescription opioid users; those who did not report any of these were coded as not current nonmedical prescription opioid users. Similar questions were asked to capture current nonmedical use of prescription anxiolytics (Xanax® or Valium® ) and current nonmedical use of prescription stimulants (Adderall® , Ritalin® , Daytrana® , Concerta® and Vyvanse® ). 2.3. Statistical analyses Pearson’s chi-squared tests were used to analyze the descriptive statistics by users of AmED and alcohol only users. Multivariate logistic regression was used to compare the relative strength of associations between use of AmED and the stated factors. SAS 9.4 was used for all analyses. 3. Results Out of 4905 13–18 year olds, 1392 (28.4%) reported consuming alcohol on one or more days in the past 30 days. Among them, 27% (n = 376) reported mixing alcohol and energy drinks in the past 30 days; the remaining youth reported alcohol only use. Among the sample, 25% reported current tobacco use and 47.1% reported current marijuana use. Similarly, 7.5%, 2.2%, and 8.8% reported current nonmedical use of prescription opioids, anxiolytics, and stimulants, respectively. Table 1 shows the sociodemographic characteristics and correlates (current tobacco use, current marijuana use, current nonmedical use of prescription opioids, anxiolytics and stimulants) by use of AmED versus alcohol only use. Univariate analysis indicated no difference by age (p = 0.59), sex (p = 0.11), area of residence (p = 0.19) or living arrangements (p = 0.13). Significant differences between users of AmED and alcohol only were found by selfreported race (p = 0.03) and average grades (p < 0.001). Specifically, Caucasians, African Americans, and Asians reported higher use of alcohol only than AmED. In contrast, Hispanics and “other” races
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reported higher use of AmED than alcohol only. Additionally, more users of AmED reported lower grades than alcohol only users. Users of AmED versus alcohol only users were significantly more likely to report current tobacco use (37.2% versus 20.5%), current marijuana use (63.8% versus 40.9%) and nonmedical use of prescription opioids (12.5% versus 5.7%), anxiolytics (4.8% versus 1.3%), and stimulants (15.7 versus 6.2%). Multivariate logistic regression predicting use of AmED indicated that sociodemographic variables were not significant predictors of such use. The odds of mixing alcohol and energy drinks (use of AmED) compared to alcohol only continued to be higher among current than non-smokers (OR: 1.63; 95% CI: 1.22, 2.17), and were twice that for current marijuana users compared to those who did not endorse current marijuana use (OR: 1.99; 95% CI: 1.52, 2.59). Moreover, the odds of mixing alcohol and energy drinks versus alcohol only were more than twice as high among those who reported current nonmedical use of used prescription stimulants (OR: 2.13; 95% CI: 1.41, 3.23) compared to those who did not report such use. Nonmedical use of prescription opioids and anxiolytics was not associated with use of AmED Table 2.
4. Discussion As far as we know, this is the first study to report the correlates of use of AmED among youth between 13–18 years of age across the US. In this study, 27% of youth used alcohol mixed with energy drinks in the past 30 days. Our findings in this younger age group were similar to the findings of studies among college students (23–56%) (Malinauskas et al., 2007; O’Brien et al., 2008; Brache and Stockwell, 2011; Miller, 2012; Patrick et al., 2014) but were higher than those among 13–20 year olds surveyed using the web (Kponee et al., 2014). We thus add to the scant literature on this use among US adolescents. Unlike the results of the study conducted among 15–19 year olds (Flotta et al., 2014) and those of college students (O’Brien et al., 2008; Miller, 2012) that found an increased risk of AmED use among males, our analyses found no difference between use of AmED and alcohol only use by sex. Just as the proportion of youth drinking alcohol has recently shifted from more male to a more genderneutral pattern (White and Huselid, 1997; Wallace et al., 2003), so has the proportion of AmED users shifted. We may have captured such a shift due to the large size of our sample and the diversity of participants. The break down by race showed slightly different choice for alcohol only versus use of AmED, but in the multivariate model, race did not predict the use of AmED. Other factors found in prior studies of energy drink and substance use were not significantly associated with use of AmED, including rurality (Cronk and Sarvela, 1997), family composition (Barrett and Turner, 2006) and school performance (Hamilton et al., 2013; Ilie et al., 2015). Behavioral factors for use of AmED were consistent with studies of older youth. For instance, current tobacco users and marijuana users were almost twice as likely to be users of AmED, consistent with other studies (Flotta et al., 2014; Hamilton et al., 2013 and Ilie et al., 2015). Martz and colleagues had also shown an association between use of AmED and marijuana use and illicit drug use (Martz et al., 2015). Two studies among college students showed an association between energy drink use and nonmedical use of prescription stimulants (Arria et al., 2010; Woolsey et al., 2014). Moreover, a study among Canadian adolescents found an association between energy drink use and nonmedical use of prescription drugs (Hamilton et al., 2013). We also found an association between use of AmED and nonmedical use of prescription stimulants among our younger national sample. The increased nonmedical use of prescription stimulants in users of AmED may be explained by two factors. First, adolescents may use energy drinks to overcome the
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Table 1 Sociodemographic and behavioral characteristics by use of AmED among 13–18 years old alcohol users (n = 1392). Characteristic
Sociodemographic Age 13–14 15–16 17–18 Sex Male Race Caucasian African American Hispanic Asian Other Area of Residence Urban Suburban Rural Average Grades As or Bs Cs or lower Living arrangement Both Mom and dad Either mom/dad Foster parents/relatives/others Behavioral Current tobacco use Current marijuana use Current nonmedical prescription opioid use Current nonmedical prescription anxiolytic use Current nonmedical prescription stimulant use * ** ***
Overall(n = 1392)
Use of AmED(n = 376, 27%)
Alcohol only use(n = 1016, 73%)
N (%)
N (%)
N (%)
p value
165 (11.8) 531 (38.2) 696 (50.0)
41 (10.9) 139 (37.0) 196 (52.1)
124 (12.2) 392 (38.6) 500 (49.2)
0.593
628 (45.1)
183 (48.7)
445 (43.8)
0.105
711 (51.2) 183 (13.2) 271 (19.5) 68(4.9) 157 (11.3)
187 (49.7) 41 (10.9) 83 (22.1) 12 (3.2) 53 (14.1)
524 (51.7) 142 (14.0) 188 (18.5) 56 (5.5) 104 (10.3)
0.0316*
605 (43.5) 567 (40.7) 220 (15.8)
161 (42.8) 165 (43.9) 50 (13.3)
444 (43.7) 402 (39.6) 170 (16.7)
0.187
984 (70.7) 408 (29.3)
238 (63.3) 138 (36.7)
746 (73.4) 270 (26.6)
0.0002**
707 (50.8) 513 (36.9) 172 (12.4)
180 (47.9) 139 (37.0) 57 (15.2)
527 (51.9) 374 (36.8) 115 (11.3)
0.126
348 (25.0) 656 (47.1) 105 (7.5) 31 (2.2) 122 (8.8)
140 (37.2) 240 (63.8) 47 (12.5) 18 (4.8) 59 (15.7)
208 (20.5) 416 (40.9) 58 (5.7) 13 (1.3) 63 (6.2)
<0.0001*** <0.0001*** <0.0001*** <0.0001*** <0.0001***
p < 0.05. p < 0.001. p < 0.0001.
Table 2 Adjusted odds ratios for the association between AmED use and sociodemographic and behavioral characteristics among 13–18 years old alcohol users (n = 1392). Characteristic Sociodemographic Age 15–16 vs. 13–14 17–18 vs. 13–14 Sex (Male vs. female) Race Caucasian vs. other African American vs. other Hispanic vs. other Asian vs. other Area of Residence Urban vs. rural Suburban vs. rural Average Grades (Cs or lower vs. As or Bs) Living arrangement Either mom/dad vs. both Mom and dad Foster parents/relatives/others vs. both Mom and dad Behavioral Current tobacco use (Yes vs. no) Current marijuana use (Yes vs. no) Current nonmedical prescription opioid use (Yes vs. no) Current nonmedical prescription anxiolytic use (Yes vs. no) Current nonmedical prescription stimulant use (Yes vs. no)
Alcohol only use
Use of AmEDAOR (95% CI)
ref ref ref
0.98 (0.64, 1.50) 1.03 (0.68, 1.57) 1.05 (0.81, 1.35)
ref ref ref ref
0.80 (0.54, 1.18) 0.62 (0.38, 1.04) 1.07 (0.68, 1.66) 0.50 (0.24, 1.05)
ref ref ref
1.18 (0.79, 1.74) 1.39 (0.94, 2.04) 1.21 (0.91, 1.59)
ref ref
0.91 (0.69, 1.20) 1.09 (0.74, 1.61)
ref ref ref ref ref
1.63 (1.22, 2.17)** 1.99 (1.52, 2.59)*** 1.27 (0.80, 2.02) 1.79 (0.80, 4.01) 2.13 (1.41, 3.23)**
ref = reference. * p < 0.05. ** p < 0.001. *** p < 0.0001.
sedating effect of alcohol; when this is not enough, they may turn to more powerful prescription stimulants. Second, adolescents may try to maximize their activation of the pleasure-reward circuit. Energy drinks, similar to prescription stimulants, have ingredients (taurine, caffeine, glucose, guarana, ginseng, etc.) that increase the
release of pleasure-reward neurotransmitters in the brain. Regular energy drink users may use both energy drinks and prescription stimulants for this purpose (Woolsey et al., 2014). Future research should test hypotheses from both of these proposed mechanisms.
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The findings reported herein are subject to several limitations. Data were cross-sectional; therefore, causal inferences cannot be drawn. Self-reported data may have been biased by social desirability or recall. However, data were collected anonymously and the time periods assessed would be easily remembered (energy drink use in the past seven days and alcohol use and mixing energy drink and alcohol questions in the past 30 days). Because we only asked if participants had used energy drinks (without regard to whether or not they mixed them) in the past 7 days, and we asked about mixing them with alcohol in the past 30 days, we had to assume that the youth who endorsed mixing were also endorsing use of energy drinks. Restricting the sample to those who had used in the past 7 days would have biased our results to those who used during both time periods. The way the question on mixing was asked might have underestimated true users if the youth misunderstood the question to only include those who mixed the drinks for themselves and did not think that premixed or drinks made by others should be included. Findings are only generalizable to alcohol users only since only alcohol users can use AmED. Moreover, important indicators of use of AmED such as personality variables, drinking motives and levels of previous substance use experience were not measured in this study and these factors might have been important. The study also has strengths. The sample size of this study was large and was highly representative of the youth in these areas according to the results of the 2010 US census (Cottler et al., 2013). We uniquely captured data among out-of-school youth through an entertainment-intercept venue method and had ethnic diversity. Social desirability bias was less likely when compared to household or school based studies since we did not require parental approval for the NMAPSS study. Youth who had been expelled or were home schooled were included while they are missing from school-based studies. Knowing the increased risks for adverse events and outcomes associated with mixing alcohol and energy drinks, we set out to identify characteristics of youth engaging in such mixing. Based on our findings, about 28% of the 13–18 years olds exhibit underage drinking and the use of AmED is common among these alcohol users, with more than a quarter reporting consumption of AmED in the past 30 days. Tobacco and marijuana use and nonmedical use of prescription stimulants are significantly associated with such use. To help prevent youth from mixing alcohol and energy drinks, prevention efforts should target youth who engage in alcohol and drug use. Drug and alcohol intervention programs should incorporate education on the risks of combining alcohol and energy drinks, as the same population is at high risk for use of AmED and alcohol/drug use. The findings herein add to the literature suggesting an association between use of AmED and the nonmedical use of prescription stimulants. Conflict of interest There are no conflicts of interest. Role of funding source N-MAPSS was conducted under contract with Pinney Associates, Inc., with funding provided by Shire Development LLC and Noven Therapeutics (PI: LB Cottler). Contributors Ms. Khan helped develop the aims, conducted statistical analyses, prepared the tables and tables and wrote the initial draft of the manuscript. Dr. Cottler was the PI of the N-MAPSS study. She had oversight over the data collection and participated in some data
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collection herself. She managed the overall study and edited each draft of this manuscript. Dr. Striley collected data and supervised the staff as well as the preparation of this manuscript including shaping the aims and methods. She was a co-investigator on the N-MAPSS study. Acknowledgement We would like to thank all the participants of this study without whose support this study would not have been possible. References Arria, A.M., Caldeira, K.M., Kasperki, S.J., O’Grady, K.E., Vincent, K.B., Griffiths, R.R., Wish, E.D., 2010. Increased alcohol consumption, nonmedical prescription drug use, and illicit drug use are associated with energy drink consumption among college students. J. Addict. Med. 4, 74–80, http://dx.doi.org/10.1097/ ADM.0b013e3181aa8dd4. Barrett, A.E., Turner, R.J., 2006. Family structure and substance use problems in adolescence and early adulthood: examining explanations for the relationship. 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Please cite this article in press as: Khan, S.R., et al., Correlates of use of alcohol mixed with energy drinks among youth across 10 US metropolitan areas. Drug Alcohol Depend. (2016), http://dx.doi.org/10.1016/j.drugalcdep.2016.04.030
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Please cite this article in press as: Khan, S.R., et al., Correlates of use of alcohol mixed with energy drinks among youth across 10 US metropolitan areas. Drug Alcohol Depend. (2016), http://dx.doi.org/10.1016/j.drugalcdep.2016.04.030