Cost-effectiveness of preventing first-episode psychosis in ultra-high-risk subjects: multi-centre randomized controlled trial H. K. Ising 1 , F. Smit 2,3,4 , W. Veling 5 , J. Rietdijk 6 , S. Dragt 7 , R. M. C. Klaassen 8 , N. S. P. Savelsberg 1,2 , N. Boonstra 9 , D. H. Nieman 7 , D. H. Linszen 7 , L. Wunderink 9 and M. van der Gaag 1,2 * 1 Department of Psychosis Research, Parnassia Psychiatric Institute, The Hague, The Netherlands 2 Department of Clinical Psychology, VU University and EMGO Institute for Health and Care Research, Amsterdam, The Netherlands 3 Department of Public Mental Health, Trimbos Institute (Netherlands Institute of Mental Health and Addiction), Utrecht, The Netherlands 4 Department of Epidemiology and Biostatistics, VU University Medical Center, Amsterdam, The Netherlands 5 Department of Psychiatry, University Medical Center Groningen, Groningen, The Netherlands 6 Department of Early Psychosis, Dijk en Duin Psychiatric Institute, Castricum, The Netherlands 7 Department of Psychiatry, Academic Medical Center, Amsterdam, The Netherlands 8 Department of Child and Adolescent Psychiatry, GGZ Rivierduinen, Leiden, The Netherlands 9 Department of Research and Education, Friesland Mental Health Services, Leeuwarden, The Netherlands Background. Although there is evidence for the effectiveness of interventions for psychosis among ultra-high-risk (UHR) groups, health economic evaluations are lacking. This study aimed to determine the cost effectiveness and cost–utility of cognitive–behavioural therapy (CBT) to prevent first-episode psychosis. Method. The Dutch Early Detection and Intervention Evaluation study was a randomized controlled trial of 196 UHR patients with an 18-month follow-up. All participants were treated with routine care (RC) for non-psychotic disorders. The experimental group (n = 95) received add-on CBT to prevent first-episode psychosis. We report the intervention, medical and travel costs, as well as costs arising from loss of productivity. Treatment response was defined as psy- chosis-free survival and quality-adjusted life years (QALYs) gained. Results. In the cost-effectiveness analysis, the proportion of averted psychoses was significantly higher in the CBT con- dition (89.5% v. 76.2%). CBT showed a 63.7% probability of being more cost effective, because it was less costly than RC by US$844 (£551) per prevented psychosis. In the cost–utility analysis, QALY health gains were slightly higher for CBT than for RC (0.60 v. 0.57) and the CBT intervention had a 52.3% probability of being the superior treatment because, for equal or better QALY gains, the costs of CBT were lower than those of RC. Conclusions. Add-on preventive CBT for UHR resulted in a significant reduction in the incidence of first psychosis. QALY gains show little difference between the two conditions. The CBT intervention proved to be cost saving. Received 25 May 2014; Revised 14 August 2014; Accepted 25 September 2014 Key words: Prevention, psychosis, quality-adjusted life years, ultra-high-risk patients. Introduction Schizophrenia is among the world’s leading causes of disability (Murray et al. 2012; Neil et al. 2014b) and is associated with substantial health-related and econ- omic costs (Neil et al. 2014a). The main driver of treat- ment costs is hospitalization. Although hospitalization costs vary from setting to setting, these have been reported to be 77% of total treatment costs, whereas unemployment is the main driver of indirect costs (Carr et al. 2003). In most patients, a first episode of psychosis is pre- ceded by a prodromal period. In the last decades this so-called ultra-high-risk (UHR) state can be detected. The UHR state is characterized by subclinical psychotic symptoms and/or a genetic predisposition and, most importantly, by functional decline and social with- drawal (Yung et al. 2005, 2008). Because 31.5% [95% confidence interval (CI) 23.8–35.0%] of people at UHR have been found to develop first-episode psy- chosis within 3 years (Fusar-Poli et al. 2012), this allows us to apply targeted prevention of a first episode of psychosis. Prevention may help to maintain quality of life, reduce the risk of onset and reduce the * Address for correspondence: M. van der Gaag, Department of Clinical Psychology, VU University Amsterdam, Van der Boechorststraat 1, 1081 BT Amsterdam, The Netherlands. (Email: m.vander.gaag@vu.nl) Psychological Medicine, Page 1 of 12. © Cambridge University Press 2014 doi:10.1017/S0033291714002530 ORIGINAL ARTICLE