Research articleLong-Term Effects of a Parent and Student Intervention on Alcohol Use in Adolescents: A Cluster Randomized Controlled Trial
Introduction
Prevention programs that involve parents as well as their children appear to be fairly successful in preventing the onset of drinking in adolescents aged <16 years.1, 2 The magnitude of effects of prevention programs curbing alcohol use in adolescents also depends on the interval between baseline measurement and follow-up. In some cases, the effectiveness of family interventions become stronger over time, with stronger and more robust effects of the interventions after a larger interval between baseline and follow-up.1 For example, the family-based intervention (Preparing for the Drug Free Years [PDFY]) of Park et al.3 showed stronger effects of the intervention over a period of 3.5 years. On the other hand, several studies showed that the effectiveness of interventions with respect to alcohol initiation decayed4, 5 or diminished6 over time. In general, relatively little data on longer-term effects (≥3 years) of parents and adolescent-based prevention regarding juvenile alcohol use have been reported.2, 7, 8, 9, 10
Spoth et al.10 argue that former studies also suffer from methodologic flaws, such as a lack of robust designs (e.g., weak experimental design), statistical power, representative samples, and theoretically founded interventions. A Dutch alcohol prevention program (prevention of alcohol use in students [PAS]) dealt with these issues. In a cluster randomized trial among a representative sample of 3490 Dutch early adolescents and their parents, the effects of a parent intervention and a student intervention were examined simultaneously as well as separately. Only when parents and their children were targeted simultaneously, the onset of (heavy) weekly drinking and the frequency of drinking were postponed effectively 10 and 22 months later.11 Targeting parents or adolescents separately did not reveal any significant effects. The PAS intervention was grounded on theoretic and empirical literature. The student part of the intervention was based on the Healthy School and Drugs program (HSD).12
In accordance with the principles of the theory of planned behavior13 and social cognitive theory,14 students were trained to develop a higher degree of self-control and more healthy attitudes about alcohol use, both strong predictors of alcohol use.15 The parent intervention consisted of a renewed Dutch version of the Swedish Örebro Prevention Program (ÖPP)16—based on research showing that a lack of rule-setting in parents is one of the best predictors of early adolescent drinking.17 Parents were informed about the negative consequences of alcohol use at an early age and they were encouraged to develop restrictive attitudes and to set strict rules toward their offspring's drinking. Mediation analyses revealed that the PAS intervention indeed modified these theory-based factors, which accounted for the delay in onset of drinking.18 The next step is to examine whether the effects of the PAS intervention also apply to the long-term follow-up, 3 years after baseline measurement.
Examining the long-term effects of interventions is important for the following reasons. It gives insight into (1) the decay or growth of effects; (2) the public health significance of the findings; and (3) various alcohol patterns over time due to the intervention.2 In addition, in this particular study, the long-term effectiveness provides insight into the strength of a brief universal multitarget prevention program focused on youth who drink at the age of 15 years, which is 1 year prior to the legal buying age in the Netherlands, whereas at the age of 15 years, 65% of Dutch adolescents already drink on a weekly basis.19 Thus, examining the long-term effects of alcohol prevention programs is an imperative step following the short-term results.
In sum, this study addressed whether the PAS intervention is effective in delaying the onset of (heavy) weekly drinking in early adolescents on the long term (34 months). In a cluster randomized trial including 3490 early adolescents, the effects of a parent and student intervention are examined simultaneously as well as separately. Relevant outcomes are onset of heavy weekly drinking and onset of weekly drinking.
Section snippets
Design and Procedure
From a list of Dutch high schools, 80 schools randomly were selected. Five schools, including 696 students per condition, were needed to power the trial to detect a reduction of 10% in weekly heavy drinking and weekly drinking relative to the control condition in a one-tailed test with a=0.05 at a power of (1b)=0.80, while accounting for 20% initial nonresponse, 30% loss to follow-up and the loss of power resulting from schools (not students) being randomized (an intraclass correlation of 0.30
Effects on Onset of Heavy Weekly Drinking
Table 2 presents the results of the interventions on the incidence of heavy weekly alcohol use at follow-up. At follow-up, significantly fewer students in the combined intervention had started to drink heavily on a weekly basis compared to the control condition (OR=0.69, p=0.00). No significant effects of either the parent intervention or student intervention were found on the incidences of heavy weekly drinking. This finding is replicated when previous alcohol use was included in the analysis
Discussion
In the present study, the long-term effects of a theory-based parent and student intervention were examined separately and simultaneously in a cluster RCT including 3490 adolescents. At 34-month follow-up, significant effects of the combined PAS intervention (parent and student) were found on both outcome measures. The onset of heavy weekly drinking and weekly drinking significantly was reduced by respectively 12.4% and 10.5% in adolescents who were targeted themselves as well as their parents.
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2019, Drug and Alcohol DependenceCitation Excerpt :However, in a much larger evaluation of the program in a different Swedish sample no evidence was found that the program was effective in delaying use (odds ratio (OR) = 0.99, 95% confidence interval (CI) = 0.61–1.60) or reducing drunkenness (OR = 1.07, 95% CI = 0.79–1.44) (Bodin and Strandberg, 2011). In an evaluation in the Netherlands, where the number of meetings was reduced from the original six to two, only a combined intervention targeting both parents and students directly had a positive effect on delaying heavy weekly alcohol use (Koning et al., 2013 2011a, 2011b, 2009; Verdurmen et al., 2014). Interventions targeting parents and students separately had no effect on adolescents’ alcohol use.
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