Multisystemic therapy refers to a treatment for adolescents with severe antisocial behaviour and includes their families. It is appropriate and cost-effective for youth referred to by the juvenile justice system with serious and chronic patterns of offending and at high-risk of out-of-home placement due to the relative intensity of the treatment. Teenagers with conduct disturbances and substance abuse problems can also be included.

MST aims to address multiple risk factors associated with juvenile offending and bases itself on Bronfenbrenner’s model. Therefore, MST tries to target risk actors at multiple levels (e.g. individual; family; peer; school). MST also needs to address difficulties between the systems (e.g. caregiver interaction with teachers and peers). The factors that create barriers to the effective functioning of proximal systems must be addressed. MST thus tries to understand behaviour within its naturally occurring context. The intervention is delivered in ecologically valid environments (e.g. home; school) and whenever possible, delivered by key ecology members (e.g. teachers; caregivers).

The caregivers are seen as the main conduits of change. Interventions focus on empowering them with the resources and skills they need to be more effective. The therapist guides the caregiver efforts to successful outcomes. The main goals are improving parenting and decreasing youth association with deviant peers. The therapist works with the family and uses family strengths to overcome barriers to caregiver effectiveness. The therapist helps the caregiver design and implement interventions aimed at decreasing youth antisocial behaviour when the caregiver effectiveness increases. It is important to try and surround the adolescent with a context that supports prosocial behaviour, effectively replacing the context that contributes to antisocial behaviour.

The MST clinicians should be available 24/7 to make sure the sessions can occur at times convenient for the families. This allows the therapist to react quickly to crises (e.g. caregiver  needs evening support for drug relapse). The duration of the intervention is 3 to 5 months but is intensive.

MST does not follow a rigid manual and is based on nine principles. The interventions are designed to promote generalization and long-term maintenance. All aspects of MST must be strengths-based and the ecological strengths need to be used as mechanisms of change. The therapist thus needs to identify strengths and use these.

At the beginning of treatment, referral behaviour and other problem behaviours to be targeted are specified from the perspectives of stakeholders (e.g. caregivers). At this point, ecological strengths are also identified and perspectives on why problem behaviour keeps occurring is assessed. The desired goals are synthesized into overarching goals of the treatment. The ecological factors that appear to be driving the problem are organized into a coherent conceptual framework (i.e. fit). The therapist then outlines intermediary goals that need to be achieved to achieve the overarching goals. Based on this, specific intervention strategies are designed. The advances and barriers of treatment effectiveness are then measured and this is used to re-evaluate whether the ecological factors that drive the problem behaviour have changed. Intermediary goals are set so that ecology members can achieve them in a few days and can receive a reward to ensure treatment progress.

MST has treatment effects on delinquency (1), psychopathology (2), substance use (3), family functioning (4), peer relations (5) and out-of-home placements (6). MST seems to be effective and efficacious with a 63% reduction in recidivism and very long-term maintenance of the results. A higher therapist fidelity to MST is associated with better youth outcomes. MST seems to be useful for juvenile offenders and juvenile sex offenders as well. However, it is not clear whether it also works for youth with conduct disorder. Participation in MST seems to save a lot of costs if the treatment works.

Greater programme and therapist experience are associated with better outcomes. Ongoing organizational support is critical to the successful implementation of MST. This requires quality assurance procedures to be in place.

In short, MST:

• Addresses known risk factors.
• Focuses on the family as the key change agent.
• Provides services in the community setting and not in restrictive settings.
• Incorporates pragmatic and behaviourally-oriented intervention techniques.
• Includes well-conceived quality assurance protocols to support treatment fidelity.