Background Early‐onset child conduct problems are common and costly. A large number of studies and some previous reviews have focused on behavioural and cognitive‐behavioural group‐based parenting interventions, but methodological limitations are commonplace and evidence for the effectiveness and cost‐effectiveness of these programmes has been unclear. Objectives To assess the effectiveness and cost‐effectiveness of behavioural and cognitive‐behavioural group‐based parenting programmes for improving child conduct problems, parental mental health and parenting skills. Search methods We searched the following databases between 23 and 31 January 2011: CENTRAL (2011, Issue 1), MEDLINE (1950 to current), EMBASE (1980 to current), CINAHL (1982 to current), PsycINFO (1872 to current), Social Science Citation Index (1956 to current), ASSIA (1987 to current), ERIC (1966 to current), Sociological Abstracts (1963 to current), Academic Search Premier (1970 to current), Econlit (1969 to current), PEDE (1980 to current), Dissertations and Theses Abstracts (1980 to present), NHS EED (searched 31 January 2011), HEED (searched 31 January 2011), DARE (searched 31 January 2011), HTA (searched 31 January 2011), mRCT (searched 29 January 2011). We searched the following parent training websites on 31 January 2011: Triple P Library, Incredible Years Library and Parent Management Training. We also searched the reference lists of studies and reviews. Selection criteria We included studies if: (1) they involved randomised controlled trials (RCTs) or quasi‐randomised controlled trials of behavioural and cognitive‐behavioural group‐based parenting interventions for parents of children aged 3 to 12 years with conduct problems, and (2) incorporated an intervention group versus a waiting list, no treatment or standard treatment control group. We only included studies that used at least one standardised instrument to measure child conduct problems. Data collection and analysis Two authors independently assessed the risk of bias in the trials and the methodological quality of health economic studies. Two authors also independently extracted data. We contacted study authors for additional information. Main results This review includes 13 trials (10 RCTs and three quasi‐randomised trials), as well as two economic evaluations based on two of the trials. Overall, there were 1078 participants (646 in the intervention group; 432 in the control group). The results indicate that parent training produced a statistically significant reduction in child conduct problems, whether assessed by parents (standardised mean difference (SMD) ‐0.53; 95% confidence interval (CI) ‐0.72 to ‐0.34) or independently assessed (SMD ‐0.44; 95% CI ‐0.77 to ‐0.11). The intervention led to statistically significant improvements in parental mental health (SMD ‐0.36; 95% CI ‐0.52 to ‐0.20) and positive parenting skills, based on both parent reports (SMD ‐0.53; 95% CI ‐0.90 to ‐0.16) and independent reports (SMD ‐0.47; 95% CI ‐0.65 to ‐0.29). Parent training also produced a statistically significant reduction in negative or harsh parenting practices according to both parent reports (SMD ‐0.77; 95% CI ‐0.96 to ‐0.59) and independent assessments (SMD ‐0.42; 95% CI ‐0.67 to ‐0.16). Moreover, the intervention demonstrated evidence of cost‐effectiveness. When compared to a waiting list control group, there was a cost of approximately $2500 (GBP 1712; EUR 2217) per family to bring the average child with clinical levels of conduct problems into the non‐clinical range. These costs of programme delivery are modest when compared with the long‐term health, social, educational and legal costs associated with childhood conduct problems. Authors' conclusions Behavioural and cognitive‐behavioural group‐based parenting interventions are effective and cost‐effective for improving child conduct problems, parental mental health and parenting skills in the short term. The cost of programme delivery was modest when compared with the long‐term health, social, educational and legal costs associated with childhood conduct problems. Further research is needed on the long‐term assessment of outcomes.

A community-based randomized controlled trial (RCT) was conducted in urban areas characterized by high levels of disadvantage to test the effectiveness of the Incredible Years BASIC parent training program (IYBP) for children with behavioral problems. Potential moderators of intervention effects on child behavioral outcomes were also explored. Families were included if the child (aged 32-88 months) scored above a clinical cutoff on the Eyberg Child Behavior Inventory (ECBI). Participants (n = 149) were randomly allocated on a 2:1 ratio to an intervention group (n = 103) or a waiting-list control group (n = 46). Child behavior, parenting skills, and parent well-being were assessed at baseline and 6 months later using parent-report and independent observations. An intention-to-treat analysis of covariance was used to examine postintervention differences between groups. Statistically significant differences in child disordered behavior favored the intervention group on the ECBI Intensity (effect size = 0.7, p < .001) and Problem subscales (effect size = 0.75, p < .001). Intervention effects on child hyperactive-inattentive behaviors and social competence, as well as parent competencies and well-being, were also found. Moderator analyses showed that the effects of the IYBP intervention on the primary child outcomes were not moderated by child or family demographic characteristics or risk factors. The results demonstrate the effectiveness of the IYBP in alleviating problem behavior among children and in improving well-being among families living in disadvantaged areas. The findings also highlight the importance of parental intervention in early childhood for parents and children most in need of support.