Aims: Psychotic disorders are one of the main causes of chronic disability in young people. An at-risk mental state (ARMS) is represented by subclinical symptoms that precede the first episode of psychosis (FEP). The PsyYoung project aims to optimize the detection of an ARMS while reducing unnecessary psychiatric treatments. It investigates the effects of service changes on the referrals and outcomes of young people with ARMS or a FEP. Methods: Six psychiatric outpatient clinics in three cantons (Basel-Stadt, Vaud, and Geneva) participated in the project. They passed through an implementation phase including service changes and the adaptation of a standardized stepped care model for diagnosis and assessment, in addition to measures for increasing the awareness, networking and training of local professionals. Preliminary results: All participating cantons had entered the implementation phase. By March 2023, there were 619 referrals to participating sites. A total of 163 patients (37% FEP and 31% ARMS) and 15 close relatives had participated in individual longitudinal assessments, and 26 patients participated in qualitative interviews. Conclusion: This national collaborative project addresses the issue of early intervention for emerging psychoses, and creates spaces for fruitful reflections and collaboration in Switzerland. The ultimate aim of PsyYoung is to harmonize clinical practices in early intervention of psychosis on a national level.

Clinical High Risk for Psychosis (CHR) states are associated with an increased risk of transition to psychosis. However, the predictive value of CHR screening interviews is dependent on pretest risk enrichment in referred patients. This poses a major obstacle to CHR outreach campaigns since they invariably lead to risk dilution through enhanced awareness. A potential compensatory strategy is to use estimates of individual pretest risk as a 'gatekeeper' for specialized assessment. We aimed to test a risk stratification model previously developed in London, UK (OASIS) and to train a new predictive model for the Swiss population. The sample was composed of 513 individuals referred for CHR assessment from six Swiss early psychosis detection services. Sociodemographic variables available at referral were used as predictors whereas the outcome variable was transition to psychosis. Replication of the risk stratification model developed in OASIS resulted in poor performance (Harrel's c = 0.51). Retraining resulted in moderate discrimination (Harrel's c = 0.67) which significantly differentiated between different risk groups. The lowest risk group had a cumulative transition incidence of 6.4% (CI: 0% - 23.1%) over two years. Failure to replicate the OASIS risk stratification model might reflect differences in the public health care systems and referral structures between Switzerland and London. Retraining resulted in a model with adequate discrimination performance. The developed model in combination with CHR assessment result, might be useful for identifying individuals with high pretest risk, who might benefit most from specialized intervention.