Marianne Welmers

Alliance and Treatment Outcome 59 CHAPTER 2 Limitations of the study The present study has several limitations. An important methodological limitation is the small number of studies included in the meta-analyses that investigated the association between split alliances and treatment outcome (five studies reporting on 17 effect sizes) and the association between alliance change scores and treatment outcome (three studies reporting on 15 effect sizes). Therefore, conclusions from these analyses should be interpreted with caution, and require future re-evaluation when a larger body of evidence has accumulated. Second, some categorical variables in the moderator analyses contained relatively few studies, which resulted in insufficient statistical power of the analyses. This was the case for all moderator variables in the associations between split alliances and outcome, and alliance change scores and outcome as a result of the small number of studies included in these meta-analyses. For the association between level of alliance and treatment outcome, the problem of insufficient statistical power might especially apply to problem type, treatment setting, treatment model, referral source and several outcome characteristics. A final limitation is that in the current meta-analysis, alliance-outcome associations were analyzed across a variety of research designs, ranging from uncontrolled pre-post designs to quasi-experimental designs. It could be reasoned that the strength of alliance- outcome associations differs considerably across research designs. Therefore, future research –based on a larger body of evidence than is currently available– may benefit from a finegrained analysis of the moderating effect of research designs on the alliance- outcome association in general. Implications for future research The sample of studies included in the present study shows that the association between alliances processes and treatment outcome has received less attention within specific treatment contexts. Treatment contexts that differ from the regular context of family- involved treatment for youth problems (i.e., family therapy in an outpatient clinic with families seeking help for a specific problem of their adolescent) might lead to different behaviors of clients, demanding different alliance building skills from therapists. Research on alliance in specific contexts, such as home-based interventions, interventions for multi-problem families or families receiving mandated treatment, might lead to a better understanding of how alliance processes are related to outcome within these specific contexts.