Background: The effects of psychotherapy in reducing aggressive behaviours in children and adolescents using meta-analysis were estimated.
Method: Sixty-five studies were included, covering 4,971 cases. Teacher reported change in aggression, change in social functioning, and changes in parental distress were calculated.
Results: The mean effect size (ES) of change in aggression in studies with untreated controls was 0.62 and in studies without untreated controls the ES was 0.95. In studies with or without untreated controls, the ESs in teacher reported aggression was 0.41 and 0.63, the ESs in changes in social functioning was 0.42 and 0.49, and the ESs in changes in parental distress was 0.39 and 0.47, respectively.
Conclusion: Psychosocial treatments aimed at reducing aggressive behaviour have positive effects and additional treatment effects are moderate. In the moderator analysis, studies with untreated controls obtained significantly larger ESs if the sample size was small. Similarly, in studies without untreated controls, studies presenting diagnostic information, and studies with younger children resulted in significantly larger ESs, and studies applying behavioural interventions obtained significantly larger ESs as compared to studies applying family therapeutic interventions. There is still a need to further develop effective outpatient interventions for children being disruptive, and especially for adolescents.