We tested the effectiveness of the preventive behavioral parent training (BPT) program, The Incredible Years (IY), and the independent effects of previously suggested sociodemographic and intervention-based moderator variables (i.e., initial severity of externalizing problem behavior, child gender, social economic status, family composition, and number of sessions parents attended), in a large-scale randomized controlled trial. Questionnaire and observation data from 387 parents and children ages 4–8 years (Mage = 6.21, SD = 1.33, 55.30% boys) across pretest, posttest, and 4-month follow-up were analyzed, using full intention-totreat analyses and correcting for multiple testing. IY was successful in decreasing parent-reported child externalizing behavior (Cohen’s d = 0.20 at posttest, d = 0.08 at follow-up), increasing parent-reported (d = 0.49, d = 0.45) and observed (d = 0.06, d = 0.02) positive parenting behavior, and decreasing parent-reported negative parenting behavior (d = 0.29, d = 0.25). No intervention effects were found for reported and observed child prosocial behavior, observed child externalizing behavior, and observed negative parenting behavior. Out of 40 tested moderation effects (i.e., 8 Outcomes × 5 Moderators), only three significant moderation effects appeared. Thus, no systematic evidence emerged for moderation of IY effects. The present multi-informant trial demonstrated that many previously suggested moderators might not be as potent in differentiating BPT effects as once thought.

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doi.org/10.1016/j.beth.2016.08.002, hdl.handle.net/1765/122505
Behavior Therapy

Weeland, J., Chhangur, R., Van der Giessen, D., Matthys, W., Orobio de Castro, B., & Overbeek, G. (2016). Intervention Effectiveness of The Incredible Years. Behavior Therapy. doi:10.1016/j.beth.2016.08.002