Our results reported that a third of adolescents in Europe (33.9%) consumed alcohol mixed with energy drinks during the past year. This prevalence is similar to that found in the USA (Schulenberg et al. 2020). Students engaging in risk-taking behaviours showed higher odds of being AmED consumers (daily tobacco smoking, illicit drug use, heavy episodic drinking, truancy at school, engaging in physical fights, etc.). On the contrary, lower odds were found for reading books for enjoyment, having other hobbies, higher parental educational level, low or medium family economic status and parental monitoring of Saturday night activities.

Similar to other studies examining the relationship between drugs, nonmedical prescription stimulant use and AmED use (Snipes and Benotsch 2013; Woolsey et al. 2015; Housman and Williams 2018), we found significant relationships between illegal substances use and AmED. The multivariate logistic regression analysis indicated that students who used inhalants, cocaine/crack, NPS and cannabis were more likely to use AmED. Energy drink use and subsequent drugs use during adolescence seem to be related, despite that the causal mechanisms remain unknown (Arria et al. 2017). This represents a particularly fragile population of high-risk adolescents who should be noted by health professionals and substance use and misuse prevention specialists.

In line with previous studies providing laboratory evidence (double-blind, within-subjects, placebo-controlled study design) that AmED beverages lead to a greater desire to drink alcohol versus the same amount of alcohol consumed alone (Marczinski et al. 2016), our results show that students engaged in heavy episodic drinking (binge drinking and intoxication) were more than twice as likely to use AmED.

Consistent with previous comparisons of driving behaviour among AmED consumers (Brache and Stockwell 2011), the odds of being AmED users was higher for the students involved in an accident while driving, even only at univariate analysis level. The differential development of acute tolerance may explain why many studies observe higher rates of impaired driving for AmED consumers (Marczinski et al. 2018). In a study testing subjective versus objective measures of alcohol intoxication, young adults reported feeling that they had less impaired motor coordination when they consumed AmED compared to when they consumed only alcohol (Ferreira et al. 2006).

In the same way, a positive relationship was found between AmED use and experience of physical fights, serious arguments and truancy at school, as reported in other studies (Howland and Rohsenow 2013; Azagba et al. 2013). A survey on college students who consumed AmED highlighted that they were at increased risk of being injured or hurt (O’Brien et al. 2008); in addition, we found association with experience of deliberately hurting themselves. Hence, especially risk behaviours that are deliberately inflicted should be taken seriously by prevention specialists.

Hypotheses of association between risk-taking and AmED consumption were also supported for engagement in sexual intercourse without a condom and trouble with police: these behaviours increased the likelihood of AmED use after controlling for all the other variables. Also in previous studies, AmED consumption was associated with an increased likelihood of specific behaviours, including sexual behaviour and aggressive behaviours (Snipes and Benotsch 2013; Berger et al. 2013).

Our data show that students going out in the evening and around with friends are at greater odds for AmED consumption. Conversely, AmED use decreases when students read books for enjoyment and have other hobbies, such as playing an instrument, etc., thus supporting the evidence that organized and constructive leisure-time activities protect against common risky behaviours in adolescence (Badura et al. 2017). Tobacco use every day in the past month is also associated with AmED consumption. This is in line with previous studies indicating that AmED use could be a potential marker for smoking susceptibility among never-smoking adolescents (Azagba and Sharaf 2014).

Given this high variability, the countries were grouped to analyse the influence between positive and negative associations at personal- and family-level in countries presenting a low to high prevalence of AmED.

Our results clearly show that in Europe there is not a well-defined spatial distribution of youth AmED consumption prevalence. This may suggest that, in the case of AmED, differently from other risk behaviours (i.e. alcohol use) (Bendtsen et al. 2014), cultural factors depending on geographical proximity may play a very limited role or are outweighed by the influence of country socio-economic indicators or individual factors.

Regarding cross-country comparisons, parents schooling college or university, being involved in serious arguments and in an accident while driving were statistically significant only for the high group, suggesting that such behaviours could be related to widespread use of AmED. On the contrary, going out in the evening, around with friends just for fun, having other hobbies, engaging in sexual intercourse without a condom, in binge drinking, in intoxication drinking alcoholic beverages and using cannabis in the past year remained significant for all low, medium and high groups, indicating that the consumption of AmED is associated with serious consequences even when the prevalence of use is low.

The uneven results of the multivariate analysis stratified by country groups deserve further investigation, in future work the socioeconomic context of each country should also be considered. This might contribute considerably to a clearer explanation of the observed between-country variability.

The most remarkable strength of the study is the use of a consistent methodology throughout 35 European countries, resulting in a very large sample of adolescents, although the question about AmED is adopted only in 17 countries. Furthermore, all samples had a national geographical coverage, except for Finland, where the Åland Islands were not covered by the sampling frame. The student representativeness was large in the majority of the participating countries, as well as the students’ response rate (average 86%) (ESPAD Group 2020). The students were recruited and surveyed with homogeneous procedures in each country, in terms of inclusion and exclusion criteria and outcome measures. The questionnaire was adapted to the common language of each country through a strict translation and back-translation process. Furthermore, to the best of our knowledge, this study on young AmED users comprises the largest geographic area reported so far.

With regard to limitations, our study does not account for quantity of consumption. Students were asked on how many occasions in the past 12 months they had used alcohol mixed with energy drinks, regardless of the intake amount. Comprehensive research that takes into consideration the role of alcohol intake in determining risk-taking behaviours is needed. Disinhibition as a consequence of acute alcohol intoxication is well-recognized, with a linear relationship between breath alcohol concentration and risk of negative behavioural outcomes (e.g. falls and injuries, motor vehicle accidents) (Taylor et al. 2010). Moreover, we do not know whether beverage consumption characteristics (i.e. ED and alcohol use) were associated with greater risk-taking during AmED sessions to determine whether they are preventable risk factors for AmED risk-taking.

Another limitation to be mentioned concerns the ESPAD methodology. All participants were 16-year-old students. Future studies should include students of different ages. ESPAD is a survey conducted only among high school students: the findings of this study may therefore not be extendable to young people not involved in education pathways. In addition to common limitations of self-reporting data (e.g. memory recall biases and social desirability biases), since ESPAD is a cross-sectional study, it is clearly not possible to establish causal directionality of the revealed relationships.