Preventing Binge Drinking in Adolescents
Results from a school-based, cluster-randomized study
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Background: In a survey taken in Germany in 2015, 14.1% of the 12– to 17-year-olds surveyed had practiced binge drinking at least once in the preceding 30 days. The school program “Klar bleiben” (“Keep a Clear Head”) was designed for and implemented among 10th graders. The participants committed themselves to abstain from binge drinking for 9 weeks. We studied whether this intervention influenced the frequency and intensity of binge drinking.
Methods: This cluster-randomized controlled trial was carried out in 196 classes of 61 schools, with a total of 4163 participants with a mean age of 15.6 years (standard deviation 0.73 years). Data were collected by questionnaire in late 2015, before the intervention and again six months later. The primary endpoints were the frequency of consumption of at least 4 or 5 alcoholic drinks (for girls and boys, respectively) and the typical quantity consumed. This trial was registered in the German Clinical Trials Registry (Deutsches Register Klinischer Studien, DRKS) with the DRKS ID number DRKS00009424.
Results: At the beginning of the trial, there was no difference between the intervention group and the control group with respect to the primary endpoints. After the intervention, differences were found among participants who had consumed alcohol before the trial (73.2% of the overall sample): binge drinking at least once in the preceding month was reported by 49.4% of the control group and by 44.2% in the intervention group (p = 0.028). The mean number of alcoholic drinks consumed in each drinking episode was 5.20 in the control group and 5.01 in the intervention group (p = 0.047).
Conclusion: The intervention was effective only in the large subgroup of adolescents who had previously consumed alcohol: they drank alcohol less often and in smaller amounts than their counterparts in the control group.
Alcohol consumption is widespread among the German population. In recent years it has remained at a constantly high level of almost 10 L of pure alcohol per person per year (1). Calculations based on epidemiological models put the number of 18– to 64-year-olds who have consumed alcohol within the last 30 days at approximately 37 million (2). Almost 12 million people in this age group also engage in occasional binge drinking, defined as consumption of 5 or more alcoholic drinks on one day in the last 30 days. According to the World Health Organization’s Global status report on alcohol and health, this makes Germany a high-alcohol-consumption country (3). High consumption figures are relevant medically and for health policy, because in 2015 alcohol consumption was one of the 10 main factors responsible for reduced quality of life and premature death worldwide (4).
Alcohol remains by far the most popular drug among adolescents. Although occasional weekly alcohol consumption among adolescents is falling slightly (5, 6), consumption is widespread among adolescents in Germany and is ranked as high in international comparisons (7). Germany’s Federal Centre for Health Education (Bundeszentrale für gesundheitliche Aufklärung, BZgA) estimates that in 2015 almost 70% of 12– to 17-year-olds in Germany had already drunk alcohol, and that approximately 1 in 7 adolescents had consumed 4 or more alcoholic drinks on at least one of the last 30 days (6).
Alcohol consumption reduces coordination and the ability to react and at the same time increases the readiness to take risks. Alcohol consumption among adolescents can have direct adverse consequences, including vandalism, violence, sexual assault, suicide, and accidents (8). Furthermore, brain development is not yet complete during adolescence, so frequent alcohol consumption in particular can lead to an accelerated decrease in volume in the frontal and temporal cortical structures—important for behavior control and memory— and reduced growth of white matter (9). In addition, there is mounting evidence that adolescents who frequently consume large quantities of alcohol maintain this consumption pattern in adulthood, rather than giving it up. This leads to the associated danger of subsequent alcohol-related problems (10).
Various behavioral preventive measures have been developed in Germany to prevent binge drinking in adolescents. Examination of 208 alcohol prevention projects revealed that only 11 of the prevention programs were suitable for investigation of their efficacy. Two of these studies were rated as having adequate methodologies (11): one controlled trial on the elementary-school program Klasse2000 (“Class 2000”) showed that at follow-up 36 months after the end of grade 4 of elementary school (age 10, thus age 13 at follow-up) alcohol consumption was lower in the intervention group than in the control group among adolescents who had already consumed alcohol (12). The findings of a cluster-randomized study on the alcohol prevention program Aktion Glasklar (“Action Crystal Clear”), aimed at students in their first year of secondary school (age 10 to 12) a significant preventive effect on binge drinking in adolescents one year after the end of the intervention (13).
This study aims to investigate the efficacy of a new school-based approach to preventing binge drinking in adolescents. This initiative is applied to class groups and aims to establish a social norm of not binge drinking.
The school-based prevention program Klar bleiben (“Stay clear-headed”) aims to reduce binge drinking and to develop a responsible attitude to alcohol. It is aimed at grade 10 classes (age 15 to 16) and is implemented by teachers. Students in the participating classes undertake to refrain from binge drinking for 9 weeks. This undertaking is put in writing by all the students signing a class contract (contract management). Every 2 weeks, the drinking behavior of the students is recorded as a class. The aim is for at least 90% of the class not to engage in binge drinking. Classes that remain “binge-free” throughout then enter a raffle to win prizes. The intervention also includes four ideas for class activities on the subject of alcohol (eBox 1).
This study is a cluster-randomized, two-arm controlled trial (14). Students in the intervention group took part in the ‘Klar bleiben’-program from January to March 2016. During the same period, those in the control group pursued the normal school curriculum instead of undergoing any specific intervention. Both groups completed a preintervention questionnaire in November and December 2015 and a postintervention questionnaire between April and July 2016, concerning their alcohol consumption. Randomization was performed at the school level to rule out interference between the intervention and control groups (eBox 2).
The study was approved by the relevant education authorities of the states of Schleswig-Holstein and Lower Saxony and was rated as ethically sound by the ethics committee of the German Psychological Society (Deutsche Gesellschaft für Psychologie, DGPs). The students’ parents were informed of the study in writing and had the opportunity to oppose their children’s participation in it.
Participants and procedure
A priori power analysis showed a required sample size of at least 3000 students and 150 classes (eBox 3). A flow diagram illustrates enrolment, randomization, follow-up, and data analysis of the sample (Figure 1). Additional information is provided in eBox 4.
Primary outcomes: The primary outcomes of the study were frequency, intensity, and consequences of binge drinking. To define binge drinking, the 5+/4+ measure has been established in the international literature (15). This uses the following questions to ascertain whether adolescents have ever engaged in binge drinking: “Have you ever had 4 or more (girls)/5 or more (boys) drinks of alcohol on one occasion?” (Yes/No). The following question determines the frequency of binge drinking: “How often do you drink 4 or more (girls)/5 or more (boys) drinks of alcohol on one occasion?” Possible answers are as follows: “Never,” “Less than monthly,” “Monthly,” “Weekly,” “Daily or almost daily.” The answers were converted into a binary outcome for statistical analysis: “Monthly” or more frequently versus other answers.
The question “When you drink alcohol, how many drinks of alcohol do you typically drink on one day?” is used to determine the intensity of binge drinking. The following prompt is provided: “One drink of alcohol is approximately 0.3 L beer, 0.1 L of wine/champagne, or 0.04 L (2 glasses) spirits.” The possible answers are numbers from “1” to “10 or more.”
The CRAFFT-d (Car, Relax, Alone, Forget, Friends, Trouble) Screening Test was used to ascertain any associated alcohol-related problems (16) (eBox 5).
Secondary outcomes: Secondary outcomes included general alcohol use (lifetime prevalence, current consumption), social factors (susceptibility, perceived descriptive norm), alcohol-related cognition (reasons for drinking, self-efficacy regarding alcohol, expected effects of alcohol), and use of other substances (cigarettes, cannabis/marijuana) (eBox 6).
Social demographics and covariates: Age, sex, religion, and type of school were documented. The language mostly spoken at home was recorded as an indicator of a migrant background. Parents’ level of education was recorded as an indicator of socioeconomic status. Alcohol consumption in students’ environment, in terms of friends, was recorded using the question “How many of your friends drink alcohol?” Possible answers were “None,” “Not many,” “Some,” “Most,” and “All.” This variable was converted into binary form for statistical analysis: “Most” and “All” versus other answers. The personality traits sensation-seeking and impulsiveness were determined using the Substance Use Risk Profile Scale (17) (eBox 7).
The effects of the intervention were tested using multilevel logistic and linear regression at the class and individual levels. In addition to group and time variables and the interaction term group × time, all variables which differed substantially between the study groups at baseline were recorded as covariates (school type, religion, parents’ level of education, peers’ alcohol consumption). Analyses were performed both for the sample as a whole and for only those who had reported prior alcohol consumption in the preintervention questionnaire (73.2% of the total sample) (eBox 8).
361 students (8.7%) did not complete the study. The levels of attrition in the intervention and control groups were similar (eBox 9).
Description of sample
Table 1 shows the characteristics of the sample at baseline. Compared to the intervention group, the control group contained more university preparatory high school students and fewer students from other types of schools. In addition, the level of education of the students’ parents was higher, more students had no religious affiliation, and more students reported that their friends consumed alcohol more frequently. There were no differences between the groups in terms of whether they had ever consumed alcohol or the frequency or intensity of binge drinking. Students in the control group scored significantly higher on the CRAFFT-d test.
Frequency and intensity of binge drinking were strongly associated with the personality traits sensation-seeking and impulsiveness (eTable 1).
Effects of the intervention
Primary outcomes: For the sample as a whole, the rate of binge drinking at least once a month according to the postintervention questionnaire was 2.9 percentage points lower in the intervention group than in the control group (Figure 2). This difference was not statistically significant.
For adolescents who had already consumed alcohol, the difference in frequency of binge drinking and thus absolute risk reduction after the intervention was 5.2% percentage points. This is equivalent to a relative risk reduction of 10.4% in comparison to the control group. The adjusted odds ratio for the interaction term group × time is significant, at 1.38 (Table 2).
Figure 2 also shows the findings concerning intensity of binge drinking. For the sample as a whole, the absolute mean difference between the groups after the intervention, 0.14 alcoholic drinks per occasion, is insignificant (Table 2). Adolescents in the intervention group who had already consumed alcohol consumed significantly less on one occasion—0.19 fewer alcoholic drinks—than those in the control group (adjusted regression coefficient for the interaction term group × time: 0.19) (Table 2).
The intervention had no significant effects regarding consequences of alcohol consumption (eFigure, Table 2).
Secondary outcomes: The intervention had no significant effects regarding general alcohol use, social factors, alcohol-related cognition, or use of other substances (eTable 2).
The findings of this cluster-randomized study show that school-based intervention programs can have an effect on the frequency and intensity of binge drinking among adolescents who have already consumed alcohol. A 2011 Cochrane review on the efficacy of school-based alcohol prevention programs included 53 studies, most of which were cluster-randomized (18). Quantitative meta-analysis could not be performed, due to the great variation between interventions, study groups, and outcome measures. Six of the 11 studies that investigated alcohol-specific interventions found a preventive effect when compared to the standard curriculum. There were preventive effects either for the whole population or for certain subgroups in 14 of the 39 studies testing interventions that aimed to prevent several risk-entailing behaviors simultaneously (e.g. alcohol, tobacco, or drug use, antisocial behavior). The findings of the 3 remaining studies, which investigated interventions targeting misuse of alcohol and cannabis, drugs and alcohol, and tobacco alone, were inconsistent.
One cluster-randomized study involving a cohort of grade 7 German students (age 12 to 13) showed that school-based programs targeting younger students below the legal minimum age for purchasing alcohol could at least delay the beginning of binge drinking (13).
Our research shows that school-based, alcohol-specific interventions can also reduce the frequency and intensity of binge drinking among grade 10 students who report that they have already consumed alcohol and can purchase it legally. No effects of the intervention on associated alcohol-related problems were observed. Such problems were documented using CRAFFT-d. The very low mean values suggest a floor effect. In addition, the internal consistency of the scale was not satisfactory.
During the half-year observation period it became clear that the frequency and intensity of binge drinking and associated alcohol-related problems were increasing in both study groups. The explanation for this is that on completing the postintervention questionnaire, unlike at baseline, the students were on average 16 years old and could therefore legally purchase beer, wine, and champagne. In the very large subgroup of adolescents who had already consumed alcohol before the study, the intervention had a small preventive effect on both the frequency and the intensity of binge drinking.
This study has several limitations that must be taken into account when interpreting its findings. Despite randomization, which took the form of cluster-randomization, the preintervention questionnaire revealed differences between the study groups in terms of some variables, although not in terms of the outcome measures. Statistical analysis therefore controlled for the substantial baseline differences between the groups. Attrition of participants over time must also be taken into account: 8.7% of the participating students could not be contacted again for the postintervention questionnaire. However, a bias in the study findings is unlikely, as there was no selective attrition. In addition, the data obtained is subjective information documented using questionnaires, rather than objective measurements. Systematic tendencies in the answers given in these questionnaires are perfectly possible. For example, there may have been a tendency to give socially desirable answers, particularly in the intervention group.
There is also the question of whether the findings of this study can be extrapolated to other settings. The study was conducted in two federal states in the west of Germany, so it is at least possible that there are regional differences between these and other German federal states. For instance, it is known that more beer but less wine and spirits are drunk in southern federal German states than in northern ones (19). Finally, follow-up was possible on only one occasion, in a postintervention questionnaire a mean of 9 weeks after the end of the intervention. This means that conclusions can only be drawn on the immediate effects of the intervention program, not on its medium- or even long-term effects. The analyses presented here did not control for how well the intervention was implemented, i.e. classes in which it was implemented very thoroughly have been included in the evaluation in the same way as classes in which it was not implemented according to instructions or in which it was not completed. We have thus taken a conservative approach. Unpublished subgroup analyses indicate that the effects of the intervention were greater when it was implemented successfully and comprehensively than in classes in which implementation was rudimentary or the intervention was not implemented at all.
The findings presented here are encouraging, as is the fact that the intervention was relatively inexpensive. The core of the intervention, students entering into a contract to refrain from binge drinking, has become an established method in the primary prevention of smoking (20) but to the best of our knowledge had not previously been used in the prevention of alcohol consumption. These findings must be replicated elsewhere, and sufficiently long follow-up must be performed.
The authors would like to thank Toska Jakob, Corinna Köhler, Luise Rehermann, Milene Wiehl, Jörn Frischemeier, Markus Watermeyer, Hanife Özbek, Melanie Maida, Myriam Lemberger, Sarah C. Murray, and Lena Heister for their support in data collation. We would also like to thank all the schools, teachers, and students involved for their collaboration.
The study was sponsored by Germany’s Federal Centre for Health Education (BZgA, Bundeszentrale für gesundheitliche Aufklärung) and commissioned by Germany’s Federal Ministry of Health.
IFT-Nord both developed and evaluated the intervention.
Conflict of interest statement
The authors declare that no conflict of interest exists.
Manuscript received on 14 November 2016, revised version accepted on 31 January 2017.
Translated from the original German by Caroline Shimakawa-Devitt, M.A.
Prof. Dr. phil. Reiner Hanewinkel
Institute for Treatment and Health Research
24114 Kiel, Germany
For eReferences please refer to:
eBoxes, eTablesn, eFigures:
2014. Geneva: World Health Organization.
Prof. Dr. phil. Hanewinkel, Dr. phil. Tomczyk, Dr. rer. nat. Isensee
Federal Centre for Health Education, Cologne, Germany: Michaela Goecke, MA
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