Discussion
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DER
The results of the present cost-effectiveness analyses indicate that the three forms of PE do not differ in costs, when taking the societal perspective. In addition, differences in gains in QALYs based on the EQ-5D-5L between treatments were negligible. As such, in light of medical decision making, the overall impression is one of equivalence of the three interventions. Only some small differences between treatment conditions could be observed. In the PE condition, societal costs were lower compared to the other conditions and this is therefore the preferred treatment option at a low WTP. At a high WTP, however, gains in QALYs based on the EQ-5D-5L were slightly in favour of the i-PE treatment condition. Also, (non-mental) healthcare costs and QALYs based on the VAS were in favour of i-PE, possibly owing to the shorter period of active treatment duration. Between-person differences could play a role in the group differences, such as the considerable individual differences in professional home care hours and work loss, which are also reflected by the relatively large standard errors. Despite these findings in favour of (i-)PE, a pronounced preference for any one of the three evidence-based treatments cannot be made based on the main outcomes of our economic evaluation, i.e. total societal costs and QALYs based on the EQ-5D-5L.Based on the findings of the current health-economic evaluation, i-PE and STAIR + PE could therefore be treated as equivalent to PE by policy makers when considering implementation. It is well known that treatment preference positively influences patients’ satisfaction as well as treatment outcomes and dropout (Windle et al., The cost-effectiveness of i-PE and STAIR + PE compared to PE has not been studied until now. Although we were unable to compare the three exposure therapies to treatment as usual and no treatment, it could be assumed that all three variants of exposure therapy are more cost-effective than treatment as usual and no treatment, based on previous findings (von der Warth et al., 