Multisystemic Therapy (MST) is an evidence- and family-based treatment for youth with serious aggressive and delinquent behavior. Despite randomized controlled trials demonstrating short- and long-term effectiveness of MST, arrest is still a concern for many youths who complete treatment. Prior studies examined risk factors for arrest after MST treatment but accounted for risk at pre-treatment rather than over the course of treatment and failed to consider the combined impact of risk and protective factors by the end of treatment on long-term outcomes. Models of resilience suggest that when faced with cumulative stress, the effects of family could serve as a protective factor that promotes either stabilizing, enhancing, or reactive effects. As such, the current study examined family environment (i.e., cohesion and flexibility) at the end of treatment as a moderator of relations between cumulative stress by the end of treatment and the likelihood of arrest at follow-up. Results demonstrated that high family cohesion and flexibility served as protective factors by decreasing the likelihood of arrest when cumulative stress was low
however, these effects faded as cumulative stress increased. These results suggest the protective effects of known targets of MST (i.e., family cohesion and flexibility) do not buffer against post-treatment arrest for all youth in treatment. Treatment targeting family cohesion and flexibility is less likely to be effective in preventing arrest for youth that continue accumulating stressful life events during treatment. Results of this study suggest that MST treatment should be further tailored to account for these families.