the same child. But it would be interesting to analyze both parents separately to see
if they report differently. Fourth, because strict methodological criteria for inclusion
were conducted, 10 effect studies were not included in this meta-analysis. This metaanalysis
has assurance that the synthesis is based on only the best evidence, but its
results may summarize only a narrow research domain.
Directions for Future Research
Despite these limitations, this meta-analysis suggests that the Level 4 system of the
Triple P intervention is a worthwhile intervention to both prevent and treat behavior
problems in children. At the same time, because of the above-cited limitations, further
research is necessary. First, it may be useful to conduct more meta-analyses with all
other instruments in the studies on Level 4 Triple P, giving us more insight into the
effects of Triple P on Parental competences (De Graaf, Speetjens, Smit, & De Wolff,
2008), giving us more insight into differences between mothers and fathers, and
enabling the impact of Triple P on parental mental health to be examined. We are
also interested in the differences in effect sizes for the different delivery formats, especially
in the Self-Help Triple P, because of the promising effects in this meta-analysis.
Furthermore, it would be worthwhile to conduct meta-analyses on some other levels
of Triple P. A second direction for future research is to conduct more in-depth analyses
on the influences of the age and gender of the child on the effects of the Triple P
intervention. Because the long-term effects of studies with fewer boys were found
to have significantly larger long-term effects on behavior problems than studies with
more boys, it would be interesting to conduct more research on the influence of this
moderator. Third, it would be interesting to examine whether the observed maintenance
effects up to 3 years postintervention occur over a longer period into children
adolescence. A fourth suggestion is to tentatively add one or two more randomized
trials on Self-Directed Triple P to this meta-analysis. In a cumulative meta-analysis,
it can be established whether the Self-Directed Triple P is more effective than the
therapist-assisted Triple P interventions.
3.6 Conclusion
This meta-analysis was conducted to assess the effectiveness of Level 4 of the Triple
P multilevel intervention system on behavioral and emotional problems of children
across different target groups and intervention modalities. This level of intervention
is part of a multilevel suite of interventions designed as a public health strategy to
promote better parenting. It contains different delivery formats. We were interested in
the pooled effect sizes of the measures of disruptive behavior in children directly after
the intervention and after 6 and 12 months. The results indicate that the interventions
using Level 4 of Triple P improve the behavior of the child, as observed by the parents.
Improvements in children’s behavior are sustained over time and seem to even improve
somewhat in the long term. Because the analyses involved both prevention universal
52 Trimbos-instituut
samples and high-risk samples, the effect sizes are very large for a universally offered
public health intervention. The positive effects of Triple P shown in this study seem to
support the widespread adoption and implementation of the program in an increasing
number of countries in quite diverse cultural contexts around the world.