Multisystemic Therapy for Problem Sexual Behaviour (MST-PSB)

Multisystemic Therapy for Problem Sexual Behaviour (MST-PSB) is for families with a young person between the ages of ten and 17 who has committed a sexual offence or demonstrated sexually abusive behaviour. MST-PSB therapists work closely with the family and others (such as the young person’s school) to prevent further sexual abuse and improve the family’s functioning.

MST-PSB has established evidence of reducing young people’s sexual reoffending and problem sexual behaviours, other antisocial behaviour and the need to go into care or prison.

Please click here to download a PDF version of full programme description

How it works (Theory of change)

  • MST-PSB is informed by ecological theory that assumes that the young person’s problematic sexual behaviour is multi-determined by risks that occur at the level of the child, family, school and community.
  • MST-PSB also assumes that the young person’s caregivers are usually the primary agent of change.
  • MST-PSB therapists therefore works closely with the young person and his or her parents to develop a plan that increases their parenting effectiveness, improves communication within the family, decreases any denial that may exist regarding the child’s sexual behaviour and increases the safety to others.
  • Family denial decreases, parenting effectiveness increases, family communication improves and harmful sexual behaviour decreases.
  • The young person is ultimately less likely to reoffend and the need to go into care or prison is averted.

What happens during delivery?

How is it delivered?

  • MST-PSB is delivered by a therapist individually to families in their homes.
  • Therapists are available 24/7 to the family and carry a caseload of three to four families at a time.
  • Therapy sessions typically last between 50 minutes and two hours.
  • The frequency of the sessions vary depending on the needs of the family and the stage of the treatment, typically ranging from three days a week to daily. Therapists work with individual families for an average of six to nine months.


What happens during the intervention?

  • A primary aim of the treatment is to ensure that the child, family, community and victims are safe. The first goal of the programme is to therefore help the family develop a risk reduction and safety plan. This plan should include well-defined strategies for reducing the young person’s access to victims. The plan should also include basic rules that the young person must agree to.
  • A second aim of the treatment is to reduce the parents and young person’s denial about the sexual offence, as this can often be a barrier to the treatment’s success.

What are the implementation requirements?

Who can deliver it?

  • Practitioners should ideally have a QCF Level 7 or 8, although in some cases a Level 6 may be sufficient.
  • Therapists can be from a variety of professional backgrounds such as social work, probation, clinical psychology and systemic family therapy.
  • MST-PSB therapists should have experience of working with violent families.


What are the training requirements?

  • All MST personnel should attend the five day core MST training course where they learn the theoretical principles underpinning MST, methods for delivering the programme and opportunities to receive feedback through role play.
  • Once initial training is completed, therapists must then attend a two day training course covering principles specific to the PSB model.
  • Training continues once therapists start to work with families. This training includes weekly telephone consultations with the MST consultant and quarterly one-and-a-half-day booster training sessions.


How are the practitioners supervised?

  • The MST team meets weekly with the onsite MST supervisor.
  • Site supervisors attend two additional days of MST training and Advisor Supervisor workshops.
  • The MST team discusses their cases with an MST expert consultant once a week by phone to obtain additional feedback and direction as needed.


What are the systems for maintaining fidelity?

Programme fidelity is maintained through MST’s Quality Assurance/Quality Improvement (QA/AI) system, which includes the following components:

  • Manuals for therapists, supervisors, consultants and organisations
  • Training and quarterly booster training for therapists and supervisors
  • Weekly consultation (via phone) with the trainer/MST Expert assigned to the team/programme
  • Onsite clinical supervision for therapists
  • Expert consultation for therapists and supervisors
  • Programme development and support for the organisation operating the MST programme
  • Validated measures of implementation adherence for therapists, supervisors and consultants
  • A web-based implementation tracking and feedback system provided through the MST Institute
  • Bi-annual Programme Implementation reviews to assess programme fidelity and drift across a number of clinical, operational, organisational and system-level processes.

Projected Costs and Benefits

This information is not yet available.


MST-PSB has established evidence of reducing the re-occurrence of sexually offending behaviour from three randomised controlled trials.


Borduin, C.M., Henggeler S.W., Blaske, D.M., & Stein, R (1990) Multisystemic Treatment of Adolescent Sexual Offenders, International Journal of Offender Therapy and Comparative Criminology, 35, 105 – 114.

  • Reductions in sexual reoffending rates (criminal records)
  • Reductions in non-sexual reoffending rates (criminal records).


Borduin, C.M., Scharfferer, C.M., & Heiblun, N. (2009). A Randomized Clinical Trial of Multisystemic Therapy with Juvenile Sexual Offenders: Effects on Youth Social Ecology and Criminal Activity. Journal of Consulting and Clinical Psychology, 77, 26 – 37.

  • Reductions in sexual reoffending rates (criminal records)
  • Reductions in non-sexual reoffending rates (criminal records)
  • Improvements in family and peer relations (parent self-report)
  • Improvements in academic achievement (parent and teacher reports).


Letourneau, E.J., Henggler, S.W., Schewe, P.A., Borduin, C.M., McCart, M.R., Chapman, J.E. & Saldana, L. (2009) Multisystemic Therapy for Juvenile Sexual Offenders: 1-Year Results from a Randomized Effectiveness Trial, Journal of Family Psychology, 23, 89 –102.

  • Improvements in problematic sexual behaviour (adolescent self-report)
  • Improvements in delinquent behaviour (adolescent self-report)
  • Reductions in substance misuse (adolescent self-report).
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