JOURNAL ARTICLE
RANDOMIZED CONTROLLED TRIAL

Effectiveness of a web-based brief alcohol intervention and added value of normative feedback in reducing underage drinking: a randomized controlled trial

Renske Spijkerman, Marion A E Roek, Ad Vermulst, Lex Lemmers, Annemarie Huiberts, Rutger C M E Engels
Journal of Medical Internet Research 2010, 12 (5): e65
21169172

BACKGROUND: Current insights indicate that Web-based delivery may enhance the implementation of brief alcohol interventions. Previous research showed that electronically delivered brief alcohol interventions decreased alcohol use in college students and adult problem drinkers. To date, no study has investigated the effectiveness of Web-based brief alcohol interventions in reducing alcohol use in younger populations.

OBJECTIVE: The present study tested 2 main hypotheses, that is, whether an online multicomponent brief alcohol intervention was effective in reducing alcohol use among 15- to 20-year-old binge drinkers and whether inclusion of normative feedback would increase the effectiveness of this intervention. In additional analyses, we examined possible moderation effects of participant's sex, which we had not a priori hypothesized.

METHOD: A total of 575 online panel members (aged 15 to 20 years) who were screened as binge drinkers were randomly assigned to (1) a Web-based brief alcohol intervention without normative feedback, (2) a Web-based brief alcohol intervention with normative feedback, or (3) a control group (no intervention). Alcohol use and moderate drinking were assessed at baseline, 1 month, and 3 months after the intervention. Separate analyses were conducted for participants in the original sample (n = 575) and those who completed both posttests (n = 278). Missing values in the original sample were imputed by using the multiple imputation procedure of PASW Statistics 18.

RESULTS: Main effects of the intervention were found only in the multiple imputed dataset for the original sample suggesting that the intervention without normative feedback reduced weekly drinking in the total group both 1 and 3 months after the intervention (n =575, at the 1-month follow-up, beta = -.24, P = .05; at the 3-month follow-up, beta = -.25, P = .04). Furthermore, the intervention with normative feedback reduced weekly drinking only at 1 month after the intervention (n=575, beta = -.24, P = .008). There was also a marginally significant trend of the intervention without normative feedback on responsible drinking at the 3-month follow-up (n =575, beta = .40, P =.07) implying a small increase in moderate drinking at the 3-month follow-up. Additional analyses on both datasets testing our post hoc hypothesis about a possible differential intervention effect for males and females revealed that this was the case for the impact of the intervention without normative feedback on weekly drinking and moderate drinking at the 1-month follow-up (weekly drinking for n = 278, beta = -.80, P = .01, and for n = 575, beta = -.69, P = .009; moderate drinking for n = 278, odds ratio [OR] = 3.76, confidence interval [CI] 1.05 - 13.49, P = .04, and for n = 575, OR = 3.00, CI = 0.89 - 10.12, P = .08) and at the 3-month follow-up (weekly drinking for n = 278, beta = -.58, P = .05, and for n = 575, beta = -.75, P = .004; moderate drinking for n = 278, OR = 4.34, CI = 1.18 - 15.95, P = .04, and for n = 575, OR = 3.65, CI = 1.44 - 9.25, P = .006). Furthermore, both datasets showed an interaction effect between the intervention with normative feedback and participant's sex on weekly alcohol use at the 1-month follow-up (for n = 278, beta = -.74, P =.02, and for n = 575, beta = -.64, P =.01) and for moderate drinking at the 3-month follow-up (for n = 278, OR = 3.10, CI = 0.81 - 11.85, P = .07, and for n = 575, OR = 3.00, CI = 1.23 - 7.27, P = .01). Post hoc probing indicated that males who received the intervention showed less weekly drinking and were more likely to drink moderately at 1 month and at 3 months following the intervention. For females, the interventions yielded no effects: the intervention without normative feedback even showed a small unfavorable effect at the 1-month follow-up.

CONCLUSION: The present study demonstrated that exposure to a Web-based brief alcohol intervention generated a decrease in weekly drinking among 15- to 20-year-old binge drinkers but did not encourage moderate drinking in the total sample. Additional analyses revealed that intervention effects were most prominent in males resulting in less weekly alcohol use and higher levels of moderate drinking among 15- to 20-year-old males over a period of 1 to 3 months.

TRIAL REGISTRATION: ISRCTN50512934; http://www.controlled-trials.com/ISRCTN50512934/ (Archived by WebCite at http://www.webcitation.org/5usICa3Tx).

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