Economic Evaluation of the SOS Training to Reduce Victimization in Dual Diagnosis Patients

Objective: Economic evaluations of interventions for dual diagnosis patients are scarce. A recent randomized controlled trial has supported the effectiveness of the Self-wise, Otherwise, Streetwise (SOS) training to reduce victimization in dual diagnosis patients. The purpose of the current study was to analyze the cost-effectiveness and cost-utility of the SOS training as an add-on to care as usual (CAU). Methods: We performed an economic evaluation from a societal perspective alongside the SOS trial. Participants were 250 dual diagnosis patients recruited at three locations from a large urban psychiatric service in the Netherlands. The main outcomes were treatment response for victimization and quality-adjusted life years (QALYs). Both costs and effects were measured across a 14-month follow-up. Results: There was no significant difference between CAU + SOS and CAU in total costs (mean difference €4,859; 95% CI [−€4,795 to €14,513]) and QALY gains (mean difference 0.0012; 95% CI [−0.05 to 0.05]). Significantly more participants in CAU + SOS achieved treatment response for victimization compared to CAU (68% vs. 54%; mean difference 0.14; 95% CI [0.02 to 0.26]). The cost-effectiveness analysis indicated an 83% likelihood that CAU + SOS resulted in a higher treatment response rate for victimization at higher costs compared to CAU. The cost-utility analysis indicated that adding SOS-training to CAU is probably not cost-effective at conventional willingness-to-pay levels for QALYs. Conclusions: At a societal willingness-to-pay of €38,000 or more per extra treatment responder, adding SOS-training to usual care is probably more attractive than usual care alone with regard to cost-effectiveness. This is a considerable willingness to pay. However, the direct costs of offering the SOS training are expected to be minor. Our findings should be interpreted with caution due to the short follow-up period and absence of data on potential reductions in police and judicial costs other than prison costs.