Hester van Eeren

| Addendum | 154 In health care, economic evaluation studies using state of the art decision analytic methods are common practice. The data used in such studies are often gathered within randomized clinical trials, but observational data are considered a valid alternative. In contrast, in Dutch youth care cost-effectiveness research and the use of available, non- randomized data are not common practice. Therefore, this thesis addressed the use and feasibility of state of the art decision analytical methods in youth care and showed how available, non-randomized data can be used when evaluating youth care. In Chapter 2 , we constructed a probabilistic Markov model to assess the cost- effectiveness of systemic interventions in youth care. To illustrate model functioning and the interpretation of the results, Functional Family Therapy (FFT) was compared to Treatment as Usual (TAU). The assumptions and parameters normally used to evaluate health care interventions were adjusted to better fit the characteristics of the systemic interventions. The treatment outcome, for example, was defined as Criminal Activity Free Years (CAFY) to address the clinical and the societal effect of the interventions. In addition, costs of resource use of the adolescents and of one of their parents were taken into account in the model, because systemic interventions are not only aimed at the referred client (i.e., the adolescent), but also at the system surrounding him or her. Resource use was defined broader than health care costs alone; The assignment to a foster home, a residential institution, or several contacts within the criminal justice system, for example, were also measured and expressed in costs per adolescent. Because the interventions were provided to youth aged 12 to 18 years and treatment effects can be expected to last into adulthood, long-term cost-effectiveness was estimated. The results of this model showed that (slightly adjusted) common economic evaluation methods are applicable in evaluating youth care. Moreover, the results can be interpreted in the same way as other economic evaluation results. These findings are an important first step towards a more systematic application of this method in youth care. The findings also led to important recommendations, such as defining an outcome that allows comparisons with other youth care interventions and taking into account costs outside the health care system (e.g., victim costs and reduced costs of avoided crimes). Because the input in a cost-effectiveness analysis can be uncertain due to imperfect or incomplete estimates of costs and effects, the decision whether or not to reimburse an intervention, based on this cost-effectiveness analysis, is marked by uncertainty. Further research may reduce this uncertainty, but is probably not without costs. The added value of future cost-effectiveness research is estimated in a value of information analysis. The aim of Chapter 3 was to investigate whether a value of information analysis, which is commonly applied in health care evaluation studies, is feasible and meaningful in youth care as well, and especially applicable to systemic interventions aimed at reducing criminal activity of adolescents. The cost-effectiveness model of Chapter 2 was used to illustrate such a value of information analysis, in which FFT was compared to the Course House (i.e., a comparative intervention on which we had literature data). Model parameters were grouped to identify those parameters that contributed most to the uncertainty and, therefore, would be most worthwhile for future research. Thereby, it was needed to assume a ‘willingness-to-pay (WTP) value’ for one CAFY (i.e., what is society willing to pay for one year without criminal activity of one adolescent?), because