Multisystemic treatment (MST) of antisocial behaviour in youth : the role of the family in facilitating change : a thesis presented in partial fulfillment of the requirements of the Doctor of Philosophy in Psychology at Massey University, Palmerston North, New Zealand

Abstract

The current dissertation includes three studies that examined (a) the overall effectiveness of Multisystemic Treatment (MST) achieved in previous outcome studies, (b) the effectiveness of MST with antisocial youth in New Zealand, and (c) a range of variables and their ability to predict MST treatment outcomes. Study 1 adopted meta-analytic strategies to evaluate the overall effectiveness of MST in comparison to other treatment approaches or usual services in the treatment of antisocial behaviour in youth. The meta-analysis integrated the results from seven primary and four secondary MST outcome studies involving 708 participants. Results indicate that across different presenting problems and samples, the average effect of MST was d = 0.55; across both instrumental and ultimate outcome measures, youth and their families treated with MST were functioning better and offending less than 70% of their counterparts who received alternative treatment or services (Curtis et al., 2004). Study 2 used a one-group pre- to post-treatment design to evaluate the efficacy of MST in New Zealand with 65 antisocial youth and their families. Results show that significant pre- to post-treatment improvements occurred in many of the instrumental and ultimate indicators of treatment outcomes. Gains were either maintained at or evident by the 6- and 12-month follow-up intervals. Study 3 examined data collected from participants in Study 2 to explore a range of variables hypothesised to predict the effectiveness of MST in New Zealand. Results show that parent and youth stages of change were significantly related to improvements in ultimate outcomes (i.e., school attendance and decreased frequency and severity of offending behaviour) at post-treatment. With regard to decisional balance, parent perceptions of youth motivation and improved family relations (pros) were positively related to their youth's readiness to change. Findings related to therapist availability indicate evidence of a potential sleeper effect in that the benefits of therapist contacts during treatment appear not to have been fully realised until follow-up periods. No valid associations were found between adherence ratings and treatment outcomes. Implications of these results for the continued refinement and dissemination of MST are discussed.