Early conduct problems include a spectrum of externalizing, antisocial, and rule-breaking behaviors, such as temper tantrums, arguing, and non-compliance. Although many young children occasionally show such behavior, some children show them more frequently and persist to show these behaviors across developmental phases (Bongers et al.
2003; Matthys and Lochman
2017). It may be hard for parents to redirect these behaviors and to avoid falling into a negative interaction pattern in which they unwillingly reinforce externalizing, antisocial, and rule-breaking behaviors (coercive cycles; Patterson
1982). Without effective family support, conduct problems in early childhood can therefore develop into disruptive behavior disorders (Loeber et al.
2000; Hoeve et al.
2008). These disorders in turn increase risk for academic problems, substance abuse, deviant peer associations, and delinquency (Capaldi
1992; Patterson et al.
2000).
The Incredible Years parenting intervention aims to prevent these unfavorable trajectories by reducing conduct problems in early childhood (Webster-Stratton
2001). It is an established behavioral parenting intervention which demonstrated immediate effects in numerous trials (see Menting et al.
2013, for a meta-analysis). During 14 weekly group sessions, parents learn relationship building techniques (e.g., play and involvement), positive reinforcement techniques (e.g., praise and celebrations), and non-violent discipline techniques (e.g., limit setting and ignore). With these techniques, parents are guided to shift their attention from negative to positive child behavior, thereby avoiding coercive interactions and increasing positive interactions. Incredible Years is recommended by the Dutch (NJI) and British (NICE) registry of evidence-based interventions but endorsed as “promising” rather than as “effective” in the USA (Blueprints) due to a lack of high-quality longer-term assessments (> 1-year follow-up).
We conducted a longer-term follow-up of the effects of Incredible Years for reducing conduct problems in a prevention setting with children who scored at or above the 75th percentile on the Eyberg Child Behavior Inventory (ORCHIDS; Chhangur et al.
2012). Immediately after the intervention and 4 months later, families showed reduced parent-reported, but not observed, conduct problems, parallel with improvements in parent-reported and observed parenting practices (Weeland et al.
2017; Weeland et al.
2018a). In this paper, we present the effects of Incredible Years on children’s broader mental health 2.5-year post-intervention.
Are there Sustained Effects on Conduct Problems?
On the one hand, the parent-perceived effects of parenting interventions such as Incredible Years may sustain. If children’s conduct problems reduce when parents participate in Incredible Years, this will probably reinforce parents’ more positive strategies, reducing conduct problems further. Related to this, when parents see that their parenting strategies reduce children’s conduct problems, feelings of parental competence and satisfaction may increase (Levac et al.
2008). In turn, this may help them keep using these strategies, also in the face of new challenges (Bandura
1977; Mouton and Roskam
2015; Deković et al.
2010).
On the other hand, the parent-perceived effects of parenting interventions such as Incredible Years may not sustain. As for any new behavior, it might be hard for parents to stay positive and use their newly learned strategies consistently in the face of new challenges and absence of therapist support. Children with conduct problems frequently challenge their parents, and conduct problems tend to be fairly persistent (Shaw et al.
2005). If parents occasionally invest less in positive interaction or give in to their child’s challenging behavior, this could put the family at risk for falling back to coercive interaction patterns. Empirically, systematic reviews and meta-analyses suggest that, across different programs, parenting intervention effects on children’s conduct problems are sustained in the longer term (Lundahl et al.
2006; Sandler et al.
2011; Sandler et al.
2015; Van Aar et al.
2017).
For the Incredible Years program specifically, randomized trials with a controlled follow-up 1 year after the intervention report mixed findings. Some show that initial effects on conduct problems were retained (Perrin et al.
2014; Brotman et al.
2008; Gross et al.
2003; Kim et al.
2008; Lavigne et al.
2008), while others show that initial effects had faded out (Reedtz et al.
2011; Stewart-Brown et al.
2004). What explains this variation remains unknown.
The only longer-term randomized controlled trial of Incredible Years (> 1 year, including follow-up data of control group) included assessments 5 to 10-year post-intervention (Scott et al.
2014). Results suggested sustained improvements in conduct problems for children in a clinical setting, but not for children in a prevention setting. This might in part be because effect sizes tend to be smaller in prevention settings (Leijten et al.
2018). To be able to detect smaller effect sizes, larger sample sizes are needed. The sample size of 109 families in the prevention trial by Scott et al. (
2014) may have been too small to detect such smaller prevention effects. Other follow-up studies have been reported, but due to waitlist control designs, follow-up data for control groups were not available. We conducted a longer-term (albeit shorter than Scott and colleagues) follow-up including the control group in a large randomized controlled trial (
N = 387), to ensure sufficient power to detect smaller effects on children’s conduct problems.
Are there Broader Benefits of Incredible Years on Children’s Development?
Without intervention, coercive interactions and conduct problems can evolve into additional problems across different developmental domains. This might be due to the psychological burden and social isolation or marginalization that children may experience because of the negative interactions with parents, other authority figures, and peers that result from their conduct problems (e.g., dual failure model; Capaldi
1992). More specifically, children’s conduct problems may lead to accumulating experiences of failure and rejection by parents and, if carried forward to the school context, by peers and teachers that may contribute to depressive feelings. Thus, the fact conduct problems often co-develop with other mental health problems (e.g., Overbeek et al.
2001; Beauchaine and McNulty
2013) raises the question whether a parenting intervention that reduces children’s conduct problems also prevents broader mental health problems, such as peer problems or emotional problems.
Previous research indicates that, indeed, parenting interventions may yield broader benefits in the longer term. In trials of the New Beginnings Program and Family Bereavement Program—aimed at teaching effective parenting skills, active listening skills, and behavior management strategies to increase positive family interactions—significant reductions in emotional problems and substance use were found at 6-year and 15-year follow-ups which, at the 6-year follow-up, coincided with significantly increased self-esteem, educational goals, and job aspirations. Such longer-term, broader benefits of parenting interventions may come about because the improvements in parenting cause an increase in children’s competencies and self-regulation abilities (see Sandler et al.
2011), which in the longer term may be related to a range of positive child development outcomes (Eisenberg et al.
2010).
For the Incredible Years program specifically, the evidence for broader parenting intervention effects is mixed. Some trials indeed suggest broader benefits of Incredible Years on emotional problems (e.g., Webster-Stratton and Herman
2008), but others did not find this (e.g., Stewart-Brown et al.
2004), and a recent individual participant data meta-analysis found no support for such broader benefits (Leijten et al.
2018). Although no clear-cut explanations can be presented to explain these mixed findings, they may have come about as consequence of differences between studies in sample size, measurements, and sociodemographic sample characteristics.
Importantly, estimating broader benefits requires well-powered longer-term assessments, because broader effects may be even smaller than effects on the targeted behavior and may need time to evolve before they become apparent. In addition, broader benefits are ideally assessed using multiple informants, because children’s peer problems are not always observable for parents (Winsler and Wallace
2002), nor are negative emotions and feelings (Sourander et al.
1999). Therefore, only longer-term assessments with multiple informants, including teachers and children themselves, can rigorously test whether Incredible Years has broader benefits on children’s peer problems and emotional problems.
In addition, many children with conduct problems show symptoms of attention-deficit/hyperactivity disorder (ADHD; prevalence of comorbidity is 24–33%, Waschbusch
2002). These symptoms include inattentive, impulsive, and hyperactive behaviors that are related to underlying neuropsychological deficits, such as sustained attention and inhibitory control (American Psychiatric Association
2013). In contrast to conduct problems, ADHD symptoms are less driven or maintained by parenting practices (Burke et al.
2008) and may therefore be less likely to change when parenting changes (hence, the development of more ADHD-specific programs, e.g., Sonuga-Barke et al.
2006). Although previous research has generally shown favorable effects of Incredible Years and other parenting interventions on parent-reported ADHD symptoms (Leijten et al.
2018), less is known about whether such effects speak to the core of the ADHD construct—assessed as children’s inhibitory control ability. Indeed, parenting interventions generally do not reduce ADHD symptoms as reported by blind assessors (Daley et al.
2014). Thus, in addition to reports of blind assessors and parents, neuropsychological tasks can provide information on whether parenting interventions could alleviate core deficits in sustained attention and inhibitory control.
Finally, it is important to know whether Incredible Years reduces parents’ and children’s service use. Conduct problems lead to increased societal costs, primarily because children with conduct problems need special education and mental healthcare more often than children without conduct problems (Gustavsson et al.
2011; Romeo et al.
2006). When children’s conduct problems reduce, their service use may reduce, because they may be less likely to drop out from regular schools, and their parents may be less likely to seek additional professional help regarding their child or childrearing. Indeed, one previous study demonstrated that receiving the Incredible Years parenting intervention was associated with less use of additional mental healthcare (Weeland et al.
2017). In this study, we will examine whether Incredible Years impacts families’ service use in the years after intervention (e.g., use of special education services, use of additional mental healthcare related to parenting or child behavior problems).