Elsevier

Addictive Behaviors

Volume 38, Issue 4, April 2013, Pages 2032-2039
Addictive Behaviors

A cluster randomized trial on the effects of a parent and student intervention on alcohol use in adolescents four years after baseline; no evidence of catching-up behavior

https://doi.org/10.1016/j.addbeh.2012.12.013Get rights and content

Abstract

Objective

It is questioned whether the alcohol prevention program “Prevention of Alcohol use in Students” (PAS) is effective in reducing the prevalence of heavy weekend drinking and the amount of drinking among adolescents at the age at which they are allowed to buy alcohol in The Netherlands (16 years). In addition, it is questioned whether the intervention effects are attributed to a delay in onset earlier in adolescence or to the development of skills due to the PAS intervention (mediation analyses).

Design

A cluster randomized trial including 3490 Dutch early adolescents (M age = 12.66, SD = 0.49) and their parents randomized over four conditions; 1) parent intervention, 2) student intervention, 3) combined intervention and 4) control group.

Outcome measures

Outcome measures were prevalence of heavy drinking and amount of weekend drinking measured at age 16, 50 months after baseline.

Results

Only when parents and students were targeted simultaneously could the prevalence of heavy weekend drinking (b =  .44, p = .02) and the amount of alcohol use (b =  .24, p = .02) be reduced. No significant effects of the separate parent and student interventions were found. The effect of the combined PAS intervention on heavy weekend drinking and amount of drinking can be attributed to respectively the increase in self-control and strict parenting, and a delayed alcohol initiation earlier in adolescence.

Conclusions

The current study confirms the effectiveness of the combined PAS intervention up to the legal drinking age of 16. The results underline that postponing the onset of drinking among early adolescents is not only crucial for health development in the short term, but also impacts the development of a healthier drinking pattern later on.

Highlights

► The long-term (mediation) effects of a parent-student alcohol prevention program. ► Adolescents are followed up to the legal drinking age, 50 months past baseline. ► Combined intervention curbs heavy weekend drinking and the amount of drinking. ► Self-control and strict parenting are important for reducing the incidence of heavy weekend drinking. ► Incidence of drinking is important to lower the amount of alcohol use one year later.

Introduction

Although declining, the rate of alcohol use among early adolescents in The Netherlands remains high. In 2010, 39% of 14-year-old adolescents drank on a monthly basis and this percentage increases to 71% at the age of 16 (van Dorsselaer et al., 2010). Moreover, once adolescents have started to drink, they tend to drink high amounts of alcohol. The use of alcohol at an early age is associated with several (health) risks later in life (e.g. substance abuse; DeWit, Adlaf, Offord, & Ogborne, 2000). Therefore, several attempts have been undertaken to postpone the onset of drinking until the age of 16, the legal buying age in The Netherlands. Studies have shown that prevention programs targeting adolescents as well as their parents demonstrate most promising findings (Smit et al., 2008, Spoth, Greenberg and Turrisi, 2008, Turrisi et al., 2009).

The present study reports findings from a randomized clinical trial of Prevention of Alcohol use in Students (PAS), a universal prevention program for adolescents (aged 12–15) and their parents. Previous reports show that only when adolescents as well as their parents are targeted does the PAS program effectively postpone the onset of (heavy) weekly drinking at 10, 22 and 34 months after baseline (Koning et al., 2009, Koning et al., 2011a). The parent intervention motivated parents to develop strict attitudes and to set restrictive rules about alcohol (Van der Vorst et al., 2005, Yu, 2003), whereas the student intervention encouraged the development of healthy attitudes about alcohol and self-control (Kam et al., 2009, Pasch et al., 2009) in adolescents. Mediation analyses show that the change in these theory-based factors indeed accounted for the effect of the PAS intervention at age 14 (Koning, van den Eijnden, Engels, Verdurmen, & Vollebergh, 2011b). Targeting parents or adolescents separately did not reveal any significant effects. Following these findings on the short- and long-term effectiveness and on mediation effects, it is important to examine the effect of PAS on the alcohol use of adolescents who have reached the legal buying age of 16, four years after baseline.

Adolescence is characterized by an increase in risk-taking behavior as a result of a higher susceptibility to peer influence and a lower level of impulse control (Steinberg, 2005). Concurrently, parents of adolescents tend to become less strict over time for the benefit of the adolescent's autonomy (Masche, 2010). Moreover, until only recently Dutch parents were advised to teach their children to drink moderately by occasionally offering them an alcoholic drink at home under their supervision during their early or middle adolescence. In this way, it was believed that at the age of 16, these adolescents would be more capable of dealing with alcohol in a responsible way. However, parents participating in the PAS program were encouraged to set restrictive rules in order to postpone the onset of drinking among their offspring until at least the age of 16, which is the legal buying age for light alcoholic drinks in The Netherlands. From then on, parental and societal restraints are lowered drastically. Moreover, the reactance theory (Brehm & Brehm, 1981) predicts that by restricting the use of alcohol, adolescents may respond with reactance once they turn 16. From this perspective, the PAS program may have a side effect that these adolescents are more likely to rapidly develop a pattern of irresponsible (excessive) drinking. The possibility of adolescents catching up their drinking behavior as a result of delayed drinking following the PAS intervention may put the relevance of delaying the onset of drinking into perspective. This makes it imperative to examine the effects of PAS in 16-year-old adolescents.

On the other hand, there are more reasons to believe that the previously obtained effects of the combined intervention sustain at the 4-year follow-up. First, fewer adolescents have started drinking before the age of 16 in the combined intervention compared to the control condition (Koning et al., 2009, Koning et al., 2011a). As a result, they may have developed a non-consumption habit over a period of years (Ouellette & Wood, 1998), which is known to be a strong predictor of future drinking behavior (Norman, 2011). In fact, an early age of onset is associated with stronger increases and higher levels of alcohol use during middle and late adolescence (Behrendt, Wittchen, Höfler, Lieb, & Beesdo, 2009). It can therefore be assumed that students in the combined intervention are likely to drink less alcohol at the age of 16 when they are allowed by their parents to drink alcohol. Second, adolescents in the combined intervention have developed a higher level of self-control, an important skill to resist peer pressure (Kam et al., 2009) and a protective factor for a diversity of drinking behaviors (Connor et al., 2011, Norman, 2011). These adolescents' parents are also more restrictive regarding alcohol use, a parenting practice that proves to be effective along adolescent development (Abar et al., 2009, Koning et al., 2012, Van der Vorst et al., 2006). It is thus likely that adolescents in the combined PAS intervention are more equipped to restrain their drinking (in line with Koning et al., 2011b), even when allowed to drink. The delay in onset as well as the development of relevant skills (self-control and strict parenting) may both increase the likelihood of finding long-term effects (Spoth, Redmond, & Shin, 2001) of the PAS intervention. In case long-term effects are found, it will be interesting to see which of these mediating factors (delayed initiation or development of skills) actually accounts for the effectiveness of PAS in 16-year-olds.

Nearly all adolescents in The Netherlands have initiated drinking before the age of 16 (85%; van Dorsselaer et al., 2010). Among these early adolescents (ages 12 to 16), a small percentage (9.4%) is involved in high-risk drinking (10 or more glasses on a weekend day). Drinking a high quantity of alcohol is related to major health risks, mainly in younger adolescents (Bava & Tapert, 2010). In previous reports, we examined the effects of PAS on the onset of (heavy) weekly drinking (Koning et al., 2009, Koning et al., 2011a, Koning et al., 2011b). Due to the high prevalence of drinking among Dutch adolescents aged 16, and the fact that PAS promoted the delay in onset until at least age 16, we are now interested in the effects of PAS on heavy drinking outcome measures. Hence the current study takes into account the effects of the PAS intervention on prevalence of heavy drinking and amount of drinking among adolescents aged 16, 50 months after baseline.

The research questions in the current study are twofold. First, we tested whether the favorable effects of the PAS intervention on adolescents under the legal drinking age sustain at age 16. Second, it is investigated whether the effects of PAS are due to change in the intervention-induced factors (self-control, rules and parental attitudes about alcohol) or to the delayed initiation of drinking. The research questions are tested in a cluster randomized trial including 2937 adolescents and their parents who participated from age 12 to 16.

Section snippets

Design and procedure

Nineteen secondary schools were randomly assigned by an independent statistician to one of the four conditions: (1) parent intervention, (2) student intervention, (3) combined student–parent intervention, and (4) control condition (business as usual). Randomization was carried out centrally, using a blocked randomization scheme (block size 5) stratified by level of education, with the schools as units of randomization. Within each participating school, all first-year students in different

Alcohol use at follow-up

Descriptive data of adolescents participating in the PAS program are depicted in Table 1. At follow-up, more than one quarter of the adolescents drink heavily (27%). On average, adolescents drink 3.7 glasses (SD = 3.4) on a weekend day.

Effects on heavy weekend drinking

Table 2 presents the results of the interventions' effects on the prevalence of heavy weekend drinking at age 16 (T4). At follow-up, significantly fewer students in the combined intervention had reported drinking heavily compared to the control condition (b =  .40, SE

Discussion

When adolescents turn 16, the legal buying age for light alcoholic drinks (beer and wine) in The Netherlands, a possible strong decline in parental strictness may result in “catching up” behavior among adolescents who postponed onset of alcohol use in the course of our alcohol-reduction intervention (PAS). The current study examines the long-term effects of the PAS intervention on heavy drinking (prevalence and amount) among 16-year-olds and their parents (50 month follow-up). The findings

Role of funding sources

This study was funded by grant number 6220 0021 from the Dutch Health Care Research Organization (Z.O.N.-M.W.) and the Dutch Ministry of Health, Welfare and Sport. Both funding sources had no role in the study design, collection, analysis or interpretation of the data, writing the manuscript, or the decision to submit the paper for publication.

Contributors

Vollebergh, Verdurmen and Engels designed the study and wrote the protocol. Koning carried out the study and wrote the first draft of the manuscript. Van den Eijnden significantly contributed to the improvement of the manuscript. All authors contributed to and have approved the final manuscript.

Conflict of interest

None of the authors have a conflict of interest.

Acknowledgments

We acknowledge the schools, teachers, students and parents who were involved in the study.

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