Treatment of young people with severe conduct disorder is, as Professor Werry (1997) stated, "not for the faint hearted". In order for any treatment programme to be effective, a range of causal factors need to be addressed if a positive outcome is to be achieved (Schoenwald & Henggeler, 1999). The factors that appear to cause conduct disorder include parenting/caregiving variables, interfamilial factors (eg, marital stressors) and extra-familial factors (eg, school, peers). Currently, the treatment modality that addresses these factors with the largest effect sizes is Multisystemic Therapy (MST) (Fraser et al., 1997).

MST uses both cognitive behavioural and family systems interventions, and is designed for use with young people who are still living at home with their families/whanau or caregivers. The first controlled study of MST with juvenile offenders was published in 1986, and since then, three randomised clinical trials with violent and chronic juvenile offenders have been conducted. In these trials, MST has demonstrated long-term reductions in criminal activity, drug-related arrests, violent offences and incarceration. This success has led to several randomised trials and community-based studies aimed at extending the effectiveness of MST to other populations of youth presenting serious clinical problems and their families.

Although treatment in the community is ideal and cost-effective, for some young people a residential placement is required. This is often due to the severity of their antisocial behaviour, the difficulty the family are having in controlling the young person's behaviour at home and/or care and protection concerns in the home environment. Effective treatment for young people in residential care includes the use of social learning principles and parent management training for caregivers. These principles form part of the treatment plan that enables the young person to reintegrate into a more stable home environment (Chamberlain, 1999, Kazdin, 1987; Werry, 1997).

Components of treatment programmes found to improve outcomes are those based upon cognitive behavioural therapy principles. These include social skills training and Goldstein's aggression replacement training (Goldstein, Glick and Gibbs, 1998; Kazdin, 1987). In addition, treatment of other conditions such as depression, Post Traumatic Stress Disorder (PTSD), alcohol and drug abuse, and Attention Deficit Hyperactivity Disorder (ADHD), is essential to improve and maintain effectiveness (Werry, 1997). Targeting school achievement is also found to be an effective goal if treatment gains are to be maintained (Chamberlain, 2003).